A GEO INVES disserta CHEMI TIGAT tion subm CAL AN IONS O ASHFA Em Sidney itted fo Univers — Sept D SED F YOU LL DEP ma Ga Sussex C r the deg ity of Cam ember IMENT NGEST OSITS tti ollege ree of Do bridge 2012 — OLOG TOBA ctor of P ICAL TUFF hilosophy DECLARATION This dissertation is the result of my own work and includes nothing which is the outcome of work done in collaboration, except where specifically indicated in the text. I confirm that it does not exceed the word limit required by the degree committee of Geography and does not contain work that has been submitted for a degree, diploma or other qualification at any other university. ............................................................. Emma Gatti i Acknowledgements I owe an enormous debt of gratitude to many people who assisted well beyond their duty during my PhD, and taught me about science, volcanoes, rivers, India, England, and, more generally, about life. Firstly I thank my supervisor Clive Oppenheimer. His insight, critical thinking and gentle direction have made this thesis far more than it would otherwise have been. His kind assistance always made me feel prepared. This helped me to carry on and bring this work to conclusion. He also tried to teach me good English manners. That did not work out fine. Secondly, I am very grateful for the support and teaching of my second supervisor Phil Gibbard, who has worked closely with me on the project in the past three years. His wisdom, patience and gentle manners really made working with him a pleasure. He also tried to teach me good English manners, and that did not work out either. The generous support of the Domestic Research Scholarship and the Cambridge European Trust has provided me with a solid foundation from which to do my research. Without them this thesis would not have been possible, nor would I have had the opportunity to work in Cambridge for four years. Travel in India, Malaysia and Indonesia has been fully sponsored by the Cambridge-India Partnership Fund and the SMUTS Memorial Fund, both of the University of Cambridge. Dame Sandra Dawson is especially to be thanked for her nurturing of my project in England and in India. The William Vaughan Lewis and Philip Lake Fund from the Department of Geography have allowed me to undertake my second field work in Malaysia and Indonesia. The Dudley Stamp Memorial Award (Royal Geographical Society), the William George Fearnsides Fund (Geological Society of London) and Sidney Sussex College sponsored the laboratory analyses. I particularly thank Hema Achyuthan (University of Chennai), a role model for all women who wish to pursue a career in science. Without her my field work in India would not have being possible. Hema introduced me to the Indian view of life, in which nothing is perfect but you have to let problems go, especially in science. She was right. I owe especial thanks to Igor Villa (University of Milano Bicocca) for continuously encouraging me to aim higher. His insights into the world of geochemistry, mineralogy and dark chocolate have been invaluable. He has been my teacher since my undergraduate days, and I hope he feels proud of his old “studentessa”. This research would have not been possible without the assistance of Chiara Petrone, Jason Day, Steve Boreham, Chris Jeans and Chris Rolfe. Their knowledge and continuous support exceed their role as technicians, making them outstanding scientists in their own right. In particular, Chris Jeans’ garden parties provided many of my best memories in Cambridge. His famous Christmas roast pork is an experience that should not be missed. During my project several friends helped me generously. I owe a great debt of gratitude to Jamie Blundell, who —way beyond his mission as my boyfriend— helped me in understanding how to write a scientific paper and corrected all my written creations. I got angry with him so many times that just for putting up with my ego and supporting me through difficult times, he deserves acknowledgement. During the past two years he taught me everything I know about cycling, tennis, football, rugby, basketball, handball, mountain biking, squash, badminton, real tennis, golf, ping-pong, archery, shooting, poker, snooker, darts and the Victoria Line engineering works. We went a long way together, through good and bad, and I hope that the exciting adventures are still to come. Alex Diment is a fine editor disguised in a Zoologist’s clothing. He spent days with me, teaching me how to edit my own work. I am profoundly grateful to have met him on my journey. If this thesis meets the requirements for a PhD, it is also thanks to him. Besides, since work is not everything, he provided me with accommodation for the last five months, he celebrated with me when there was no one else ii around, and he took me to eat zebra steak for the first time in my life. He made my last months in Cambridge memorable. Simon Wongsuwarn is the best of house mates. He put up with me when I was down, and gave me beer when I needed it. He sat next to me when I was lonely, and kept me company in the hardest moments, when the rain seemed as if it would never stop (June 2012) and the future bright as a November day (July 2012). Because I know that friends are rare, and no success is the result of a single effort, I consider him an integral part of my accomplishments. Eszter Kovac is an incredible woman who shared with me two crazy holidays in Italy, one year of absolutely failed rowing experiences, tears and laughter. She is hilarious and deep at the same time, and I loved to have her around. She also helped me during the proof-reading process, and wrote with me several applications in the middle of the night, tolerating without complaint my complete absence of organization. She has heard me complaining about everything so many times that I am surprised she still hangs out with me. I spent the last three years living with a group of amazing people from every part of the world. I won’t forget 19 Saxon Road and our nights in front of the TV watching The Wire (“Those are for you McNutty!”) and The Apprentice (“Stuart the brand, you are fired!”), our Sunday breakfasts at Hot Numbers, and our joint effort to try to avoid the Council Tax. For this I thank the 19 Saxon Road Crew: Jamie Blundell, Simon Wongsuwarn, Dino Ott, Sabrina Jahn and Alex Silver. In particular, Alex gave us a free TV and paid for the TV licence throughout 2011, although he had been living in Japan since 2010. So, thank you Alex. We made the most of it. I also thank my fieldwork companions: Naomi Matthews, Adam Durant, Christina Neudorf, Clair Harris, Ceri Ben Shipton, Kathryne Price, Kate Connell, Jinu Koshy, Janaradhana B., Racha Raj and Alpa Sridhar. It was —to all extent— a mind-blowing experience. I would leave again right now if I had the chance. I am particularly grateful to Sacha Jones, the writer of an impressive 700 page thesis on the Toba super- eruption. It seems that everything I did, she had done before me. Her help, suggestions and hints about living in India were life saving. I thank all my special editors and proof-readers who assisted me in polishing the language of my thesis: Amy Donovan, Tehnuka Ilanko, Kayla Iacovino, Amy Prendergast, Helena van der Merwe, Eszter Kovac, Alex Diment, Marie Edmonds and Derek Birch. Life in the Department of Geography would have not been the same without my PhD companions: Maria Angelica Godoi, Paul van der Vegt, Sebastian Gibson, Karolina Lesczcynska, Tobias Gerken, Lex Hoffmann (also invaluable San Francisco hotel companion), Priti Nigam, Andre Silveira and Isayvani Naicker. I owe you all interesting dinners involving rum on fire, Risk games in which one becomes as tense as a violin string, and general day-to-day amusements in Downing College Hall. Without you, my life would have been a simple sequence of days in and out of the office. During the last few months, the only social activity that kept me sane was kick-boxing. For this I thank the company of Einat Elmalem who shared with me the mind-numbing experience of boxercise first, and kick boxing after. We met late, but I hope our friendship will last. Finally, I must thank my mum and dad. Everything I am, think and feel comes ultimately from them. I hope I have made them proud. iii ‘Happy families are all alike; each unhappy family is unhappy in its own way’ Leo Tolstoy ‘Primary ash are all alike; each reworked ash is reworked in its own way’ A Geologist version v Summary The ~ 73 ka ‘super-eruption’ of the Toba caldera in Sumatra is the largest known eruption of the Quaternary. The products of this eruption, the Youngest Toba Tuff (YTT), have been implicated in global and regional climate deterioration with widespread ecological effects. In this thesis I study the YTT co-ignimbrite ashfall, in particular the mechanisms of transport, sedimentation and preservation of ash deposits. I use distal marine and terrestrial ash sediments: a) to estimate the volume of YTT ash fallout; b) to quantify variability in the geochemistry of YTT ash; c) to assess the reliability of YTT ash as a chronostratigraphic marker; and d) to determine local influences on the reworking of YTT ash deposits. Following the introductory chapters, I address topics a) and b) through detailed investigations of published physical and chemical evidence. Chapter three shows that particle size and sediment thickness do not decline exponentially with distance from the eruption vent, highlighting the limitations of current methods of volume estimation for co-ignimbrite super-eruptions. Chapter four analyses geochemical variation in 72 YTT samples, and reveals the signatures of magma chamber zonation and post-depositional alteration. I address topics c) and d) through fieldwork in six locations, and detailed analysis of ash samples from a wide variety of local depositional environments. Chapter five uses high-resolution stratigraphic analysis of the YTT layer in the Son Valley, India, to show that variable deposition and sediment reworking may compromise the reliability of the ash layer as an isochronous marker for interpreting archaeological sequences. Chapter six combines a new understanding of the mechanisms of reworking, using new data on microscopic characteristics of reworked ash at four sites in Malaysia to demonstrate the necessity of accounting for reworking in palaeoenvironmental reconstructions. I conclude that accurate analyses of distal ash deposits can reliably determine the chemical properties of the YTT eruption, and that a detailed understanding of deposition and reworking processes is essential to inference of the environmental impacts of super-eruptions. vii Table Of Contents Acknowledgements ............................................................................................................................. i Summary .............................................................................................................................................. v Table Of Contents ............................................................................................................................ vii Table of Tables ................................................................................................................................... xii CHAPTER 1. INTRODUCTION ............................................................. 1 1.1 The ~ 73 ka Toba super-eruption ..................................................................................... 3 1.2 Recent Toba activity ....................................................................................................... 11 1.3 The potential impact of the ~ 73 ka Toba super-eruption ............................................ 13 1.3.1 Climatic impact ........................................................................................................................ 13 1.3.2 Environmental impact ............................................................................................................. 15 1.3.3 Human impact and archaeological evidences ...................................................................... 18 1.4 Research rationale and objectives .................................................................................. 19 1.5 Thesis structure .............................................................................................................. 23 1.6 Comments on the authorship of journal papers revised as chapters ............................ 24 CHAPTER 2. RESEARCH METHODS ................................................... 27 2.1 Field methods ................................................................................................................. 27 2.2 Laboratory methods ....................................................................................................... 29 2.2.1 Electron probe microanalyses ......................................................................................... 29 2.2.2 Laser ablation ICP-MS..................................................................................................... 30 2.2.3 Malvern Mastersizer 2000 particle size analyser .......................................................... 32 2.2.4 Magnetic susceptibility .................................................................................................... 32 viii CHAPTER 3. PARTICLE SIZE, THICKNESS AND VOLUME OF THE YTT CO- IGNIMBRITE ASHFALL ......................................................................... 33 3.1 Introduction ...................................................................................................................... 33 3.2 Methods of volume calculation in ignimbrite and co-ignimbrite eruptions ................... 34 3.3 Study methods ................................................................................................................... 38 3.4 Results ............................................................................................................................... 43 3.4.1 Size characteristics of distal fallout ......................................................................................... 43 3.4.2 Thickness variations and volume ............................................................................................ 44 3.5 Discussion ......................................................................................................................... 47 3.5.1 Distribution of YTT co-ignimbrite ash as a function of particle size ........................ 47 3.5.2 Wind patterns .................................................................................................................... 48 3.5.3 Validity of volume models applied to the YTT ............................................................. 48 3.6 Conclusion ........................................................................................................................ 50 CHAPTER 4. GEOCHEMICAL PATTERNS IN PROXIMAL AND DISTAL TOBA GLASS…………… ................................................................................. 53 4.1 Introduction ...................................................................................................................... 53 4.2 Geochemistry of the YTT.................................................................................................. 55 4.3 Methods ............................................................................................................................. 57 4.4 Results ............................................................................................................................... 58 4.4.1 Analytical bias ........................................................................................................................... 58 4.4.2 Magmatic differentiation ......................................................................................................... 58 4.4.3 Post-depositional alteration ..................................................................................................... 60 4.5 Discussion ......................................................................................................................... 62 4.5.1 Analytical bias ........................................................................................................................... 62 4.5.2 Pre-eruptive magmatic differentiation ................................................................................... 62 4.5.3 Post-depositional alteration and definition of geochemical provinces .............................. 64 4.6 Conclusion ........................................................................................................................ 66 ix CHAPTER 5. STRATIGRAPHIC SIGNIFICANCE OF THE YTT LAYER IN THE SON VALLEY………….. ................................................................................ 77 5.1 Introduction ...................................................................................................................... 77 5.2 Study Area .......................................................................................................................... 79 5.3 Methods ............................................................................................................................. 83 5.3.1 Criteria for discriminating primary ash fallout and reworked tephra deposits ....... 86 5.4 Tephrostratigraphy ........................................................................................................... 86 5.4.1 Primary and secondary ash sites .................................................................................... 86 5.4.2 Sites showing only reworked ash .................................................................................... 89 5.4.3 Tephra sedimentological structures and geometry ...................................................... 90 5.5 Discussion .......................................................................................................................... 91 5.5.1 The local environment pre- and post-deposition of the YTT in the Middle Son Valley…… .......................................................................................................................................... 91 5.5.2 YTT deposits in the Middle Son Valley as a chronostratigraphic marker? .............. 95 5.5.3 Reliability of the YTT as palaeoenvironmental marker .............................................. 96 5.5.4 Reliability of the YTT as an archaeological marker ..................................................... 97 5.6 Conclusion ......................................................................................................................... 97 CHAPTER 6. DEPOSITIONAL PROCESSES AND SEDIMENTOLOGY OF YTT DEPOSITS IN THE LENGGONG VALLEY, MALAYSIA .................................... 99 6.1 Introduction ................................................................................................................... 99 6.2 Study Area .................................................................................................................... 101 6.2.1 Geomorphological setting ............................................................................................. 104 6.3 Methods ........................................................................................................................ 106 6.4 Results ........................................................................................................................... 106 6.4.1 Geochemistry .................................................................................................................. 106 6.4.2 Stratigraphy ..................................................................................................................... 109 6.4.3 Sedimentology ................................................................................................................ 111 x 6.5 Discussion .................................................................................................................... 115 6.5.1 Primary and reworked tephra: a reliable method of distinction? ............................ 116 6.5.2 Mechanisms of tephra reworking in the Lenggong valley ........................................ 121 6.6 Conclusion ................................................................................................................... 124 CHAPTER 7. CONCLUSIONS ............................................................ 127 7.1 Synthesis .......................................................................................................................... 128 7.2 Limitations of the research ............................................................................................. 130 7.3 Future research ............................................................................................................... 130 7.4 Broader implications ...................................................................................................... 132 CHAPTER 8. REFERENCES ............................................................... 135 APPENDIX. RAW GEOCHEMICAL DATA ................................................ 155 9.1 Internal Standards (in wt%) measured with LA-ICP-MS .............................................. 155 9.2 Rare elements geochemical analyses (LA-ICP-MS) ....................................................... 157 9. 3 Major components internal standards and calibration (EPMA) .................................. 175 9.4 Major components geochemical analyses (EPMA) ........................................................ 177 Table of Figures Figure 1-1. ..................................................................................................................................................... 2 Figure 1-2. ..................................................................................................................................................... 3 Figure 1-3. ..................................................................................................................................................... 4 Figure 1-4. ..................................................................................................................................................... 6 Figure 1-5. ..................................................................................................................................................... 7 Figure 1-6. ..................................................................................................................................................... 8 Figure 1-7. .................................................................................................................................................. 12 Figure 1-8. .................................................................................................................................................. 15 xi Figure 1-9. .................................................................................................................................................. 17 Figure 1-10. ................................................................................................................................................ 19 Figure 1-11. ................................................................................................................................................ 22 Figure 2-1 ................................................................................................................................................... 28 Figure 2-2 ................................................................................................................................................... 28 Figure 2-3 . ................................................................................................................................................. 30 Figure 3-1. .................................................................................................................................................. 35 Figure 3-2 ................................................................................................................................................... 41 Figure 3-3. .................................................................................................................................................. 42 Figure 3-4 ................................................................................................................................................... 43 Figure 3-5. .................................................................................................................................................. 44 Figure 3-6 ................................................................................................................................................... 45 Figure 3-7. .................................................................................................................................................. 46 Figure 4-1. .................................................................................................................................................. 54 Figure 4-2 ................................................................................................................................................... 56 Figure 4-3 ................................................................................................................................................... 57 Figure 4-4. .................................................................................................................................................. 58 Figure 4-5. .................................................................................................................................................. 59 Figure 4-6. .................................................................................................................................................. 60 Figure 4-7. .................................................................................................................................................. 61 Figure 4-8. .................................................................................................................................................. 63 Figure 5-1 ................................................................................................................................................... 79 Figure 5-2. .................................................................................................................................................. 85 Figure 5-3 ................................................................................................................................................... 88 Figure 5-4 ................................................................................................................................................... 89 Figure 5-5. .................................................................................................................................................. 90 Figure 5-6. .................................................................................................................................................. 92 xii Figure 5-7. .................................................................................................................................................. 94 Figure 6-1 ................................................................................................................................................. 102 Figure 6-2 ................................................................................................................................................. 103 Figure 6-3 ................................................................................................................................................. 105 Figure 6-4 ................................................................................................................................................. 108 Figure 6-5 ................................................................................................................................................. 110 Figure 6-6 ................................................................................................................................................. 111 Figure 6-7. ................................................................................................................................................ 114 Figure 6-8. ................................................................................................................................................ 115 Figure 6-9. ................................................................................................................................................ 117 Figure 6-10. .............................................................................................................................................. 119 Figure 7-1 ................................................................................................................................................. 128 Table of Tables Table 1-1. ....................................................................................................................................................... 5 Table 1-2. .................................................................................................................................................... 11 Table 2-1. .................................................................................................................................................... 27 Table 3-1 ..................................................................................................................................................... 38 Table 3-2 ..................................................................................................................................................... 39 Table 3-3. .................................................................................................................................................... 40 Table 3-4. .................................................................................................................................................... 50 Table 4-1 ..................................................................................................................................................... 57 Table 4-2 ..................................................................................................................................................... 67 Table 4-3 ..................................................................................................................................................... 72 Table 5-1. .................................................................................................................................................... 82 Table 5-2 ..................................................................................................................................................... 84 Table 5-3. ................................................................................................................................................... 87 xiii Table 6-1 ................................................................................................................................................... 107 Table 6-2 ................................................................................................................................................... 112 Table 6-3. .................................................................................................................................................. 116 Table 6-4. .................................................................................................................................................. 120 1 Chapter 1. Introduction Super-eruptions are rare and extreme volcanic events that have not been experienced in recorded human history. As a working definition, eruptions producing 1000 km3 or more (bulk volume) of magma may loosely be considered ‘super-eruptions’ (Figure 1-1). One of the most recent is the Youngest Toba Tuff (YTT) eruption, which occurred at what is now Lake Toba, in Sumatra, Indonesia. The lake resulted from the collapse of the Toba caldera after several very large explosive eruptions, culminating in the YTT eruption ~ 73 ka ago. In addition to voluminous ignimbrites, the YTT eruption produced a tephra fall deposit estimated at ~ 800 km3 Dense Rock Equivalent (DRE) consisting of fine volcanic ash (equivalent to a solid cube of rock measuring 9 km in each dimension). The ash is found to have a thickness of 1 cm as far as 4000 km from the vent. To put this into context, the 2010 eruption of Eyjafjallajökull, which caused the largest disruption in European civil aviation since World War II, deposited no more than 8 mm of ash at a maximum 60 km from the volcano (Bonadonna et al., 2011). YTT ash deposits have been discovered in over 100 terrestrial and marine sites in southern Asia, covering an area of at least 1.3 × 107 km2, equivalent to the combined areas of the United States and Canada. The thickness of the YTT deposits ranges from 0.1 mm in deep ocean sediments to 7 m in river valleys. These variations reflect various factors operating on what might be considered the primary ash fallout (i.e., reworking by various agents). The exceptional amount of ash erupted and the distance the ash reached suggest that the YTT is possibly the largest volcanic eruption of the last 2 million years. This thesis considers several YTT ash sites in a variety of environmental contexts, and focuses on the interactions between ash and the receiving environment. In particular, it examines the mechanisms of transport, aggradation and preservation of the metres-thick tephra sequences in terrestrial sites. The dynamics of sedimentation of distal tephra are important to a wide range of fields including Quaternary studies, Volcanology, Geochronology and Archaeology. The applications of tephrostratigraphy span from single grain micron-scale analyses to kilometre-scale stratigraphic correlations: geochemical and isotopic investigations on single ash grains can 2 determine t sequences t palaeoenvir identificatio and dating i This chapte concludes w Figure 1- eruption km3 is fin the USGS he age and housands o onmental st n of abrupt n archaeolo r introduce ith a synop 1 Comparison to have occur e ash. This is volcano Haz provenance f kilometr udies, whic environme gical recons s the YTT e sis of the res of eruption red in the pa more than t ard Program. of the ash es apart. R h use the ntal change tructions. ruption (1. t of the thes sizes based on st 2 million y he entire volu , and this i ecently, tep tephra as a s (possibly 1), the ratio is (1.3). the volume ears, with 280 me of Moun n turn can hrostratigr chronostra associated nale and go of magma. To 0 km3 of mat t Everest (230 be used to aphy has b tigraphic m with ash de als of the t ba is conside erial erupted 0 km3) Pictu link geolo een applied arker to en position its hesis (1.2), red the larges , of which 800 re courtesy o gical to able elf), and t f 1.1 The Eart larg Carb and (Pag Eura km 198 acce F c The Ros Che arou m th den for t Tab The ~ Toba calde h (Figure 1 est volcanic oniferous m Ghazali, 19 e, 1979), g sian (McCa ridge (the In 1). Its loca ntuate volat igure 1-2 a) aldera and th caldera com e, 1991), ea sner et al., nd Lake To ick near Ha se-rock equi he HDT eru le 1-1. 73 ka Tob ra, in north -2). It measu lake on th etamorphi 84). Toba is enerated by rthy and El vestigator R tion probab ile release b The Toba ca e Toba lake f plex consi ch of which 1991). The ba. This is a ranggaol (F valent (DRE ption is a fi a super-e Sumatra, res 100 km e planet (R c rocks, Mio part of the the subdu ders, 1997; idge Fractu ly coincide eneath the v ldera in Sum rom Prapat. sts of four o is associat Haranggao densely we igure 1-3). C ) volume o ssion track ruption Indonesia, i x 30 km, a ose and Ch cene sedim active volc ction of th Masturyono re Zone) th s with a b olcano (Fau atra from Go verlapping ed with an l Dacite Tu lded tuff ex hesner and f ~ 35 km3 o age of 1.2 M s the larges nd it is part esner, 1990 entary rock anic arc tha e Indian-Au et al., 200 at subducts end in th zi et al., 199 ogle Earth; b calderas (N ignimbrite ff (HDT) i posed in th Rose (1991 f material ( a by Nishim t resurgent ially occupi ). The cald s, and Quat t follows th stralian pla 1). The plat directly be e subductin 6). ) View of th ishimura et eruption (C s the oldest e northern ) estimated Table 1-1). ura et al. (1 Quaternary ed by the To era consist ernary volca e NW trend te beneath e is characte neath Toba g ridge, w e western sid al., 1984; C hesner and ignimbrite caldera wal that the HD The only pu 977), as sum 3 caldera on ba lake, the s of Permo nics (Aldiss of Sumatra continenta rised by a 2 (Nishimura hich migh e of Toba hesner and Rose, 1991 recognised ls, up to 100 T erupted a blished date marized in - l , t ; 4 Figure 1- with shor The Oldest the walls of places in wh River canyo OTT as a de by its revers 1987, Table deposits hav (Dehn, 1991 km3. The third, o the HDT (F of ~ 60 km3 3 Toba calder t red dashes. Toba Tuff ( the souther ich it has b ns and in a nsely welde e polarity ( 1-1). Knigh e recently b ; Pattan et r Middle T igure 1-3). DRE of ign a complex lo The Samosir l OTT) is exp n and easter een identifie fault block n d rhyolite tu Table 1-1). t et al. (1986 een identifi al., 1999; Le oba Tuff (M Chesner and imbrite. San cation (from C ava domes ar osed along n portions o d outside t orth of the ff (69–74 w The OTT h ) estimated ed in deep- e et al., 2004 TT), is lim Rose (199 idine dated hesner, 2012 e outlined by the wester f the calder he present c lake (Chesn t. % SiO2) d as been dat an initial D sea cores in ), increasin ited to the n 1) estimated by 40Ar/39A ). The inner orange circles n scarp of t a (Figure 1- aldera are in er, 2012). C istinguishe ed by 40Ar/ RE volume the Indian g the estim orthern wa that this e r provided a YTT collapse . he Uluan p 3, Chesner, the deeply hesner (199 d from Youn 39Ar at 840 of ~ 500 km Ocean and s ated DRE vo lls of the ca ruption ejec n age of 50 fault is shown eninsula, an 2012). The incised Asa 8) described gest Toba T ka (Diehl e 3. Yet OTT outh China lume to ~ 2 ldera, overl ted a minim 1 ka (Chesn d in only han the uffs t al., ash Sea 300 ying um er et 5 al., 1991, Table 1-1). The MTT has the same mineralogy as that of the other Toba tuffs, but it can be distinguished from them by its whole rock and mineral chemistry as well as its strontium isotopic composition (Chesner, 2012). Dehn et al. (1991) identified MTT ash in deep-sea cores from the Indian Ocean, but Chesner (2012) argues against dispersal of the MTT beyond Sumatra. Table 1-1 Characteristics and ages of the four eruptions of the Toba Caldera Complex. The Youngest Toba Tuff (YTT) is the youngest of the three major rhyolitic tuffs of Quaternary age associated with the Toba caldera (Chesner et al., 1991, Table 1-1). The eruption is partially responsible for the collapsed structure visible today (Figure 1-3); a resurgent dome formed within the caldera, consisting of two half-domes separated by a longitudinal structure called the Prapat graben (Bellier and Sebrier, 1994). Today the collapsed caldera includes all the previous calderas. The steep slopes of the caldera walls suggest the caldera collapsed along a ring fracture structure (Figure 1-2). From crude stratigraphical evidence the total magma volume of the YTT has been estimated as ~ 2800 km3 DRE, of which the ashfall accounts for ~ 800 km3 DRE (Rose and Chesner, 1987; Chesner and Rose, 1991; Gardner et al., 2002). Proximal plinian pumice fall deposits of the YTT have not been found. This led Rose and Chesner (1987) to conclude that the YTT fallout is entirely of co-ignimbrite origin. Such eruptions develop a buoyant cloud from pyroclastic density currents, rather than from the vent (Figure 1-4). In cases where the density of Unit Thickness (m) Volume (km3) Age Method References Youngest Toba Tuff (YTT) < 400 2800 73.88 ± 0.32 ka 40Ar/39Ar Storey et al. (2012) 74 ka 73 ± 4 ka 75 ka 74.9 ± 12 ka; 73.5 ± 3 ka Average 40Ar/39Ar Oxygen isotope stratigraphy K/Ar Oppenheimer (2002) Chesner et al. 1991 Ninkovich et al. (1979) Ninkovich et al. (1978a) Middle Toba Tuff (MTT) > 140 60 0.50 Ma 40Ar/39Ar Chesner et al. (1991) Oldest Toba Tuff (OTT) > 300 500 0.84 Ma 40Ar/39Ar Diehl et al. (1987) Haranggaol Dacite Tuff (HDT) < 200 35 1.2 Ma Fission track Nishimura et al. (1977) 6 the particle- the eruptive These form Wilson, 197 Huang, 198 is progressiv gas (Textor pyroclastic f 1989; Wood enter the bu of particle (A Figure 1- pyroclast formed a Wohletz, gas mixture column can ations gener 6). The flow 0). As fine a ely enriche et al., 2003) lows and ca s and Wohl oyant plum ndrews an 4 Schematic ic flows after s the buoyan 1991). is too high not becom ate dense p s segregate sh and gas e d in ash and . This gener rrying large etz, 1991). e, the result d Manga, 20 representatio the collapse t mixture of for a given e buoyant, a yroclastic fl into a dens scape from gases, and ates the co- quantities Since fine-g ing remain 12). n of a) plin of the plinian fine ash rises initial vertic nd forms a c ows that tra e lower par the dense lo becomes b ignimbrite of ash and m rained and ing pyroclas ian eruptive column, c) off the pyro al momentu ollapsing fo vel on the t and an up wer flow in uoyant beca cloud, a buo agmatic g low-density tic deposits column, b) development clastic flow ( m, the mat untain (Spa ground surf per dilute p to the uppe use of the e yant cloud ases (Sigurd particles ar are deplete fountain gen of the co-ign modified from erial rising f rks et al., 19 ace (Sparks art (Sparks r part, the l xpansion o rising above sson and C e more like d in those t erating latera imbrite cloud Woods and rom 86). and and atter f the the arey, ly to ypes l F I The intr thic outf nort volu The sout Indi et al and an B Oce igure 1-5 Th sland. tuffs depo acaldera tuf k, and are e low sheet e hern Suma mes of 1000 distal ash heaster Asi a (Korisetta ., 1995; Kar Chesner, 19 asu, 1993) an, the Ben ick YTT sem sited by th fs, an extens xposed betw xceeds 100 tra (Aldiss km3 (DRE has been re a (Figure 1 r et al., 1988 malkar et a 90; Chesne . Equivalent gal Fan, the i-welded pyro is colossal ive outflow een Prapa m in thickn and Ghaz ) caldera fill ported to -6). YTT as ; Acharyya l., 1998; We r et al., 1991 material h South Chin clastic density eruption a sheet, and d t and Porse ess and cov ali, 1984). and 1000 k cover an ar h deposits and Basu, 1 stgate et al., ; Shane et a as been rec a Sea and t current dep re known istal ash. In a (Figure 1- ers between Rose and C m3 (DRE) o ea of at lea have been i 993; Kale et 1998), Mal l., 1995) an ognised in he Arabian osits on the e as the YTT tracaldera t 5, Chesner, ~ 20,000 hesner (19 f outflow sh st 1.3 × 10 dentified at al., 1993; M aysia (Ninko d possibly in sea-floor s Sea (Ninko astern scarp o , and cons uffs are less 1998). By c km2 to ~ 30 87) crudel eets. 7 km2 in so terrestrial ishra et al., vich et al., Banglades ediments in vich, 1979; 7 f Samosir ist of thick than 100 m ontrast, the ,000 km2 o y estimated uthern and locations in 1995; Shane 1978b; Rose h (Acharyya the Indian Pattan et al. f , 8 1999; Buhri al., 2002; Liu Figure 1- YTT has The distanc remarkable ignimbrite c They argued higher mag height at wh the eruption magnitude ng et al., 20 et al., 2006 6 The distrib been identifie e reached characterist louds gene that the lar ma flux, wh ich the clou , the highe of the erup 00; Gasparo ). ution of the Y d. by the ash ics of the rated from ge source a ich in turn d starts exp r the colum tion is larg tto et al., 20 TT. Each po (more tha YTT erupti super-erupt rea (i.e., the governs th anding hor n (this prin e enough 00; Huang int represent n 4000 km on. Baines ions (M > area covere e cloud dev izontally). T ciple is bas to produce et al., 2001; s a marine co from the and Sparks 6.5) could c d by pyrocla elopment a hey therefo ed on a mo a large so Liang et al. re or terrest caldera) is (2005) sug over contin stic flows) w nd entrainm re suggeste del by Woo urce area a , 2001; Schu rial site wher another of gested that ent-sized a ould produ ent height d that the la ds, 1988). I nd an elev lz et e the co- reas. ce a (the rger f the ated 9 magmatic flux, then the model by Baines and Sparks (2005) shows that the eruption can generate giant clouds with diameters of a few thousands km, whose neutral buoyancy height can reach the stratosphere. Because of the extreme diameter these giant clouds’ radial expansion speeds are greater than typical stratospheric wind speeds and thus they are initially insensitive to winds. This allows the clouds to expand in all directions, developing diameters greater than 600 km (Baines and Sparks, 2005). The spin velocity increases with the size: thus the expansion of the giant clouds becomes controlled by a balance between gravity and Earth’s rotational forces. The Coriolis forces transform the giant clouds into spinning bodies of nearly fixed proportions. The constraints of the Earth’s rotation transforms the ash clouds into compact, rigid-body-like structures, and this helps to maintain the clouds’ integrity, so that they can carry on spinning for some time, before they become unstable owing to baroclinic disturbances and break up into eddies. Recently, Herzog and Graf (2010) questioned the assumption that the size of the source, magma flux and the neutral buoyancy height are effectively correlated. They suggested that co-ignimbrite clouds are inefficient in terms of vertical transport, because they are produced by multiple updrafts developing from the pyroclastic flow, all characterised by the same energy. They argued that the energy of each single updraft is not enough to produce a sustained umbrella cloud in the stratosphere for the time necessary to produce the spinning cloud suggested by Baines and Sparks (2005). Ninkovich et al. (1978a) provided the first age estimation for the YTT deposit. They obtained a K- Ar age of 73.5 ± 3 ka on sanidine from sample 72-0-60 from Prapat (Malaysia). The same method on biotite from sample Id680 from Si Gura Gura (Sumatra) provided an age of 74.9 ± 12 ka (Table 1-1). Chesner et al. (1991) obtained a mean age of 73 ± 4 ka for a welded tuff from Samosir Island and for an ash sample from Malaysia. Both these samples were dated using laser-fusion 40Ar/39Ar on individual sanidine phenocrysts. Later, Zielinski et al. (1996a) suggested an age of 71±5 ka based on a peak in volcanic sulphur in an ice-core from Greenland. More recently, Oppenheimer (2002) proposed a mean age of ~ 73 ka, while Williams et al. (2009) suggested an average age of 73 ± 2 ka. Storey et al. (2012) recently dated sanidine collected from YTT in the Lenggong valley (Malaysia) with 40Ar/39Ar and obtained an age of 73.88 ± 0.32 ka (Table 1-1). Earlier literature 10 refers to the YTT as dating 74 ka (Williams and Clarke, 1995; Oppenheimer, 2002) or 71 ka (Zielinski et al., 1996a; Zielinski et al., 1996b; Zielinski, 2000). The YTT eruption has been calculated to have lasted 7-14 days (Table 1-2), on a grain-size deposition model (Ninkovich et al., 1978b; Ledbetter and Sparks, 1979). The plume column has been estimated to have been 31 ± 5 km high, on the basis of a linear relationship between the height of the umbrella cloud and the magnitude of the eruption (Chesner and Rose, 1991; Woods and Wohletz, 1991). These calculations are highly model-dependent and the estimations are heavily influenced by assumption. Herzog and Graf (2010) recently modelled the spread of a co- ignimbrite plume in three dimensions, and suggested that the maximum overshooting of such an eruption does not depend linearly on the magnitude. They recalculated the initial parameters and suggested that in cases of large co-ignimbrite eruption (radius > 70 km) the maximum overshoot height is expected to reach around 20 km. Rampino and Self (1992; 1993) used the assessed duration and maximum column height to obtain the H2SO4- burden emitted by the volcano, essential to determining the climatic effect of the eruption. By studying compositions of YTT pumices and welded tuffs, they were able to suggest 1 × 1015 g of sulphate aerosols were released from the erupted magma, together with 2 × 1016 g of fine dust. Another study estimated the dissolved amount of sulphate from the composition of pyrrhotite inclusions in magnetite, and suggested that the eruption ejected a minimum of ~ 3.5 × 1015 g of H2S (Rose and Chesner, 1990) and 1 × 1016 g of sulphur aerosol into the stratosphere (Chesner et al., 1991). However, Scaillet et al. (1998) questioned this estimate which was based upon the low solubility and diffusivity of sulphur in low temperature silicic melts. A recent study on the YTT melt inclusions by Chesner and Luhr (2010) determined a sulphur content of just 6– 32 ppm by using microprobe analyses of the YTT melt inclusions. They estimated a syn-eruptive production of H2SO4 of 1014 g, two orders of magnitude less than the earlier calculation, although this estimate neglects the possibility of a separate gas/fluid phase before the eruption. It is fair to say that we have no reliable estimate of the sulphur yield of the YTT eruption. Table 1-2 summarise the extrapolated eruptive parameters. 11 Table 1-2 Modelled and estimated YTT volcanic parameters (modified from Woods ad Wohletz, 1991). Column height by a) Herzog and Graf (2010) and b) Woods and Wohletz, (1991); total volume and duration of the eruption by Chesner and Rose (1991); mass of sulphur from Chesner and Luhr, (2010) and Rose and Chesner, (1990). Total volume erupted (km3 DRE) Volume of ash elutriated (km3 DRE) Duration of co- ignimbrite column Mass eruption rate from vent (109 kg s-1) Column height (km) Mass of sulphur aerosol (g) 2840 840 7-14 days 7.1 20a to 30b 1014 or 1015 The YTT magma was sourced from a compositionally zoned magma chamber (Chesner, 1998). The compositional zoning results from the crystal fractionation occurring in the YTT source magma chamber during ~ 150 ka cycles (Bachmann and Bergantz, 2008). The result is a magma that is more evolved near the chamber roof and less evolved at deeper levels. A model described by de Silva et al. (2006) suggested that eventually water saturation and roof-magma density contrasts lead to the caldera collapse and consequent ignimbrite eruption. 1.2 Recent Toba activity The ~ 73 ka Toba eruption left a 2 km deep, steep-walled caldera, with a flat floor covered by a thick accumulation of welded YTT. Immediately following the eruption, Lake Toba began to fill with water (Chesner et al., 1996). The most evident post-eruption feature is Samosir Island, a resurgent dome that was lifted at least 1100 m to its present position (Figure 1-2a). It is unclear when resurgence began and ended, but a 14C date of 33,090 ± 570 (Chesner et al., 2000) on organic-rich lake sediments collected near the highest elevations on Samosir indicated that about 33 ka ago Samosir Island was still beneath lake level. Samosir Island is covered by the sediments of the Samosir Formation, which were deposited on the sub-lacustrine caldera floor after the filling of the Toba Lake. The formation comprises fining-upwards sequences of debris flow, volcanic breccias, and conglomerates, overlain by laminated tuffaceous sand and silt, diatomaceous clay and volcanic ash (Figure 1-7, Marel, 1947; Van Bemmelen, 1970). Since the YTT eruption, volcanic activity has continued at Toba. The northern area of Samosir Island (Pintubatu) includes active hot springs and fumaroles, and the area along the lake shore beneath Parapat and Samosir is intensely hydrothermally altered. Several overlapping lava domes 12 have been i andesitic ce side of the m formed sinc the eruption erupted in h al., 1996). Figure 1- Formatio volcanicla cm. dentified on ntres, the T ain caldera e the YTT e and now istorical tim 7 Laminated n identified o stic deposits northeaste andukbenu . Both cone ruption. An rises over 1 es, but an tuffaceous sa n the northe emerged from r Samosir a and Singg s rise ~ 500 intracalde 000 m abo active solfa nd and silt, d rn part of Sa water when Island and alang volca m above the ra volcano, ve lake leve tara is prese iatomaceous mosir Island Samosir beca near Tuk-T noes, are lo YTT outfl the Pusikbu l (Chesner, nt on its no clay and volc . The Samosi me resurgent uk (Figure cated outsi ow sheet and kit volcano, 2012). Pus rtheaster fl anic ash from r Formation , ca. 30 ka. Sca 1-3). Two s de the north appear to developed ikbukit has ank (Chesn the Samosi is a post-YTT le divisions: 2 mall ern have after not er et r 13 1.3 The potential impact of the ~ 73 ka Toba super-eruption Ever since the discovery of tephra beyond the Indian Ocean (Ninkovich, 1979), there has been speculation concerning the possible effects of the YTT eruptive event. The discussion has touched upon climate, environmental and palaeoanthropological aspects. Here each of these is addressed in turn. 1.3.1 Climatic impact It has been suggested that the YTT eruption was responsible for an extended cooling period and consequent icesheet advance at the beginning of the last ice age (Rampino and Self, 1992; Rampino and Self, 1993; Ambrose, 1998). Since volcanic sulphur aerosols are known to be the principal cause of volcanic-generated climatic perturbations, several studies have attempted to estimate the amount of sulphur emitted during the YTT event (§ 1.1). The postulated exceptional mass of sulphur released has prompted several hypotheses concerning the effect of the super-eruption on climatic deterioration. Rampino and Self (1982; 1992; 1993) proposed that the YTT led to a ‘volcanic winter’: a surface cooling of up to 5 °C caused by increased atmospheric opacity, similar to post-nuclear war scenarios. This global cooling effect, they argued, would have lasted for several years, generating up to 12 °C of cooling. A negative feedback would consequentially have developed, precipitating the Earth into a millennium of cold climate (Rampino and Self, 1993). A key paper by Zielinski et al. (1996a) argued against the ‘volcanic winter’ hypothesis, emphasising that the eruption and the millennium of cooling that occurred afterwards are unrelated. They reported a volcanic sulphate peak at about 71,100 ± 5000 year in the Greenland ice-core GISP2 (Yang et al., 1996; Zielinski et al., 1996a; Zielinski et al., 1996b), and equated it to the YTT event (Figure 1-8). Yet they showed that the ~ 1000 years of cooling between the interstadial 20 (IS20, ~ 74.5 ka) and interstadial 19 (IS19, ~ 69 ka) that Rampino and Self (1992) identified as a post-YTT cooling effect, was already underway before the eruption occurred (cf. Jouzel et al., 1987; Bond et al., 1993, Leuschner and Sirocko, 2000). This demonstrated that the YTT occurred too late to have initiated a major millennial-scale glacial period. Furthermore, it suggested that, despite the record’s indicating an increased amount of SO2-4, the sulphur emission 14 was insufficient to trigger significant climatic change. Nevertheless, they noticed that the climate system between IS20 and IS19 was in ‘shifting mode’ (i.e. highly sensitive to perturbations), and this instability could have amplified the effects of the Toba aerosols. They concluded that the magnitude and long residence time of aerosols resulted in a complex environmental feedback, which might have been responsible for a 200 years period of enhanced cooling at the beginning of the 71 ka stadial event. Yet, Oppenheimer (2002) argued that the apparent perturbations in the ice-core chemistry could reflect post-deposition reactions occurring in the highly acidic YTT horizon, and pointed out that no other ice core has yet been reported a similar peak at ~ 70 ka. However, a recent work of Svensson et al. (2012) linked the Greenland (NGRIP) and Antarctic (EDML) ice cores at the Toba eruption, using matching patterns of bipolar volcanic spikes. Nine volcanic spikes identified in both cores allowed a unique match, confirming with decadal precision that the Toba event occurred between the onsets of Greenland Interstadials (GI) 19 and 20 and the Antarctic counterpart Antarctic Isotope Maxima (AIM) 19 and 20 (Figure 1-8). A recent study simulated a 100-times-Pinatubo sulphur emission scenario (a putative YTT eruption) to investigate its possible impact on the regional climate (Timmreck et al., 2010; Timmreck et al., 2012). They found that even under interglacial conditions (capable of amplifying the eruption impact), the effects of the YTT on climate were reduced to minor changes, such as two years of reduced precipitation, anomalously strong fluvial discharges and a few decades of possible vegetation changes in which trees were replaced by grasses. They concluded that the climate changes arising from the YTT eruption were insufficient in terms of temporal scale to have drastic, lasting consequences for the biota, including humans (Timmreck et al., 2012). There is no general consensus on the climatic impact of the YTT ashfall. The initial hypotheses are strongly challenged by the evidence of more limited sulphur emissions and the lack of clear evidence of long-term global climatic shock (cf. Kilian et al., 2006). More recent studies emphasise the role of the YTT eruption in environmental change on the local to regional rather than global scale. Figu Proje arou Toba matc 74.5, shift 1.3 Foll envi Asia Mod scen in S aero re 1-8 Synch cts 2), EDM nd Greenland volcanic ma h points to s are the best in the d-exce .2 Environ owing the ronmental i . els. Robock ario by app outh Asia c sol cloud. ronization of L (EPICA Dr Interstadial tch. All reco ynchronize th candidates to ss close to the mental imp argument mpact that et al. (2009 lying a two- hanged dra the NGRIP onning Maud 20 (GI 20) a rds show δ18O e records (T represent the marker (from act of Rampin such a clim ) simulated dimensiona matically as (North Green Land), EDC nd the Antar except EDC 1-T9). Match Toba event. Svensson et o and Se atic shift cou the environ l climatic m a result of land Ice Cor (EPICA dom ctic Isotope M that is δD. points T1 to T2 is conside al., 2012). lf (1992), ld have ind mental imp odel and fo the reductio e Projects), G e C) and Do axima (AIM Nine volcani T4, whose ag red the most several stu uced in the act of a 100 und that the n of sunlig ISP2 (Green me Fuji 1 iso ) 19 and 20, c spikes have es fall in the probable due dies hypot ecosystems -times-Pina vegetation ht induced 15 land Ice Core topic profile based on the been used a interval 74.1 to an abrup hesised the of southern tubo mode distribution by the large s s - t l 16 Terrestrial proxies. Williams et al. (2009) analysed terrestrial pollen from sediments from the northern Bay of Bengal. They found a distinct change in Indian vegetation from tree and shrub before, to more open vegetation immediately following the eruption. Van der Kaars et al. (2012) studied pollen collected from the marine core BAR94-25, in the northwest of Sumatra, and suggested that the YTT instantaneously destroyed the local pine forests on Sumatra. Ambrose (2003) and Williams et al. (2009) investigated stable carbon isotopes in carbonate nodules from above and beneath the ash in the Son Valley, India. The results suggested an increase in C4 and decrease in C3 plants immediately following the YTT, corroborating the conclusion that the YTT caused a shift in local vegetation from trees to open grassland. Haslam et al. (2010) measured stable carbon isotopes from south central India, and found the same dramatic climatic shift to drier/cooler conditions after the eruption. These authors suggested that such an environmental shift lasted at least several centuries (Haslam et al., 2010; Haslam et al., 2011). Marine proxies. Schulz et al. (2002) analysed monsoon-influenced proxies extracted from core SO130-289 KL, from the northern Arabian Sea. They showed substantial interstadial/stadial fluctuations in sea-surface temperatures during the Toba interval, confirming that the Late Pleistocene was characterised by climatic instability in the region (Figure 1-9). However, the monsoon oscillations recorded by the proxies did not appear to have been influenced by the YTT event. These studies overall suggest that the YTT had a strong impact on the environment (especially the vegetation) of local areas directly affected by the ashfall (i.e. Sumatra and India) but had only a minor impact on monsoonal circulation. These discoveries initiated a reconsideration of previous conceptions of the impact of the YTT event. Oppenheimer (2002) noted that there was a large range of uncertainty in estimates of important eruptive parameters, including eruption volume, height of eruptive plume, duration of the eruption and the amount and duration of stratospheric sulphur aerosol. He suggested that the data did not provide compelling evidence for strong and enduring climatic impact. F p S U Rec were Sinc (Cam Clem asse rath igure 1-9 Pa (MAGSUS), lankton fora 76,000 yr ago tage; IS= Int k 37 –based s bulloides; (e) G ently Van de clearly lin e the Late po et al., ens and P mblages det er than vo laeoclimatic sediment acc minifer Glob ., independen er-Stadial. (a ea-surface tem ISP2 δ 18Oice r Kaars et a ked to long Pleistocene 1982; Prell rell, 2003; v ected by W lcanically-i proxy data fr umulation ra igerina bullo tly from the ) Magnetic S peratures; ( record. l. (2012) po -term trend was char and Kutzba an der Ka illiams et al. nduced effe om the Arab te, sea-surfa ides all show YTT event ( usceptibility d) relative ab inted out th s initiated a acterised by ch, 1987; P ars et al., 2 (2009) cou cts. This ian Sea core ce temperatu relative inst from Schulz (MAGSUS); undance of t at the chang few thousa oscillating rell and Ku 010; Xiao e ld have been explanation SO90-93KL. re and relat ability in the et al., 2002). (b) sediment he planktic f es determin nd years be climate a tzbach, 199 t al., 2011) linked to e has been Magnetic sus ive abundan time window MIS= Marin accumulation oraminifer G ed from pol fore the YT nd unstable 2; Kudrass , the chang xternally-d further su 17 ceptibility ce of the 64,000- e Isotope rate; (c) lobigerina len analyses T eruption monsoons et al., 2001 es in pollen riven factors pported by . ; 18 Blinkhorn et al. (2012), who re-calculated the carbon isotope ratios from specific YTT sediments sites in southern India. They obtained values related to local morphological changes rather than the presence (or absence) of the ash. Williams (2012a) concluded that the resolution of the sediments in which the proxies (both marine and terrestrials) are preserved is too low to isolate the environmental changes related exclusively to the YTT ashfall. 1.3.3 Human impact and archaeological evidences A major motive for studies of the ~ 73 ka Toba super-eruption is the need to understand the effects that the YTT event might have had on the prehistoric human populations living in Asia and elsewhere at the time of the eruption. Rampino and Self (1992 and 1993) after proposing the ‘volcanic winter’ hypothesis, argued that the supposed millennium of cold climate generated by the YTT eruption might have led to a crash in ancient modern-human population size. Ambrose (1998) developed the idea further, proposing the concept of a ‘volcanic winter bottleneck’. The author suggested that YTT ashfall were responsible for a Late Pleistocene human bottleneck (Figure 1-10, Ambrose, 1998). He speculated that the feedback caused by the volcanic winter could have induced low primary productivity and famine; thus the YTT might have had a substantial impact on human populations (Ambrose, 1998). Gathorne-Hardy and Harcourt-Smith (2003) argued against the YTT ‘bottleneck’ hypothesis, stating that there was little fossil and genetic evidence to support it. Archaeological work by Petraglia et al. (2007) in southern India supported the ‘low-impact’ hypothesis of Oppenheimer (2002), Schulz et al. (2002) and Gathorne-Hardy and Harcourt-Smith (2003). The archaeologists suggested that the impact of the ash was minimal and very short-lived, since the technology of the stone tools recovered both below and above the ash was the same (Petraglia et al., 2007). Williams (2012a) reminds us, however, that the Optically Stimulated Luminescence (OSL) dates constraining the sediment ages below and above the ash have substantial uncertainties (81–67 ka above and 83–71 ka below the ash) and so they cannot exclude the possibility of long (millennial scale) abandonment of the area. F s c Jone to th seve mod than lesse (Op 1.4 The YTT them dete In h add igure 1-10 T ubdivision d aused by the s (2010) pr e YTT even rely affected ern-human ks to the a ned the s penheimer, Resea previous se eruption. T in terms rmine the e is reviews, ressed when he Late Pleist ue to dispersa Toba-induce oposed that t, with som . This conc s were stro bundance o everity of 2009). rch ration ctions have his section of the aims nvironment Williams (2 considerin ocene ‘volcan l within Afri d volcanic win different ar e parts of s ept was supp ngly affect f local envi a local g ale and o shown that discusses t of the the al impacts c 012a, 2012 g the envir ic winter’ bot ca during the ter (from Am eas gave ris outh Asia se orted by O ed by the Y ronmental enetic ‘bot bjectives much work he many qu sis. The ini aused by th b) suggeste onmental i tleneck propo early Late Pl brose, 1998) e to differe rving as ref ppenheimer TT conse diversities a tleneck’ an has gone in estions that tial goal of e YTT ashfa d that a fun mpact of th sed by Ambr eistocene is f . nt palaeoan ugial areas w (2012), wh quences, bu vailable in d enabled to understa remain una this study ll. damental i e YTT is t ose, (1998). P ollowed by b thropologic hilst other o suggested t recovered India. These rapid re- nding the im nswered, an was to re-e ssue that n he availabil 19 opulation ottlenecks al responses s were more that ancien afterwards conditions colonisation pact of the d addresses xamine and eeded to be ity of high t - 20 resolution, accurate environmental proxy records directly related to the tephra. Jones (2010) recommended the addressing of two issues: the rate of accumulation of the secondary tephra and the time/seasonality of the eruption, since the local climate could drastically amplify or reduce the effects of the tephra accumulation (cf. Todesco et al., 2004; Favalli et al., 2006). Three objectives were therefore established in this study: a) to find high resolution proxies directly related to the YTT; b) to assess the rate of accumulation of reworked deposits; and c) to investigate the time and seasonal setting of the eruption. However, while reviewing the literature on the subject, several recurring issues related to the use of the tephra deposits were identified. Accordingly, the research was reoriented to focus on the following questions: 1) What is the primary thickness of the YTT? Thickness, together with grain size, is the most important and discussed characteristic of the tephra, since it is used in models and simulations to assess the eruption’s environmental impact (i.e. Rose and Chesner, 1987, Robock et al., 2009). However, the thickness varies substantially from site to site. Several previous studies used an approximated average thickness, but it is not clear how such constraints were obtained. It is therefore necessary to understand how the ash is distributed and accumulated, the variability of particle sizes and how the deposit's thickness varies with distance from the source, and to assess the uncertainty inherent in estimating these physical factors. 2) What is the geochemical variation in YTT glass? Geochemical fingerprinting is the accepted method by which YTT deposits are identified and correlated (Westgate and Gorton, 1981). Because of the large body of literature available, it is common to use geochemical data from published studies for comparison with new results. The question therefore arises of the extent to which analyses performed in different laboratories are comparable. Could the depositional environment modify the geochemistry of the glass? The variability of the major chemical components in the YTT has not hitherto been closely examined. Yet, given the large amount of geochemical data collected for the YTT since the 1930s, it seems appropriate to compare the available chemical evidence and in addition to investigate the causes and effects of chemical variations. 21 3) How reliable are previous reconstructions of the YTT environmental impacts? Assessments of the environmental impact of the YTT are typically based upon evaluation of proxies collected from sediments immediately under- and overlying the YTT horizon. However, several studies have used the YTT as chronostratigraphic marker without distinguishing whether the material was primary ash (deposited during fallout and instantaneously preserved in situ) or secondary ash (redeposited ash material possibly mixed with non-volcanic clastic products). Reworking processes such as erosion, fluvial and aeolian transport, floods, soil flow and landslides can disturb the tephra sequence, depositing the ash on younger or older sediments. The reliability of the YTT as a chronostratigraphic marker in sedimentary sequences therefore needs to be studied. 4) Which mechanisms are behind the transport, accumulation and preservation of the thick, widespread, YTT fall deposits? The largest part of the YTT tephra in distal deposits at terrestrial sites is composed of ‘secondary’ tephra, metres-thick sequences of reworked volcanic material, occasionally mixed with non-volcanic sediments (Figure 1-11). As will be shown in chapters five and six, the characteristics of the YTT tephra are therefore a consequence of a range of environmental processes acting, with the passage of time, upon and interacting with the ash. Thus, in order to isolate the impact of the YTT on the receiving ecosystems (using environmental proxies collected from the tephra sediments), it is necessary first to determine how the ash has been modified by local factors, and whether the tephra are suitable for palaeoenvironmental reconstruction. The recent discovery of new sites in the Malaysia peninsula has finally allowed the interpretation of the interactions between YTT ash and the receiving environment. The objectives of the present study derive from the desire to answer the questions proposed by previous studies and the challenges exposed during review of the literature on the YTT eruption. As a consequence, it was decided directly to address the four questions identified above, and indirectly, in relation to the results, to discuss the suggestions of Williams (2012a) and Jones (2010). Hence, keeping the main goal in mind (re-examine and determine the environmental impacts caused by the YTT ashfall) this thesis tackles the following objectives: a) to review the literature on particle size and thickness of the YTT fallout and synthesise the evidence to re-evaluate the volume of the co-ignimbrite ash. 22 b) to r (mo disc c) to a Vall d) to e sedi The next sec Figure 1-11 R m in thicknes eview and stly from overed. ssess the re ey, India. valuate the ments for p tion offers eworked YTT s in this area. synthesise p distal tephr liability of mechanism alaeoenviron a synopsis o deposits in J ublished an a fall depo the YTT te s of tephr mental rec f the remain walapuram, s d new evid sits) and phra as a c a reworkin onstruction ing chapter outhern India ence on th to evaluate hronostrati g, and asse s. s of the diss . The rework e YTT gla agents of graphic ma ss the relia ertation. ed volcanic m ss composit any variab rker in the bility of te aterial can re ions ility Son phra ach 7 23 1.5 Thesis structure This work is based on sedimentological and stratigraphic data collected during two field seasons in 2009 (India) and 2010 (India, Malaysia, Indonesia), as well as geochemical analyses of ash collected in the field. The backbone of the thesis is the study of the dynamics of the ash and its receiving environment, focusing on distal tephra deposits. Following this introduction, Chapter two outlines the methods and techniques employed to acquire primary data. Chapters three and four review the physical and chemical parameters of the YTT as reported in the literature. Chapter three discusses the most recent volume calculations and proposes an alternative estimate, taking into account the variation (or lack of) in thickness with distance from source. The size of the YTT ash finer-grained (< 60 μm) particles is poorly correlated with distance from the source. Below a certain grain-size the motion of the particle is dominated by the viscosity of the air rather than by the inertia of the particle itself (as particles get smaller, the Reynolds number of the fluid goes down). Fine ash particles therefore behave more analogously to the motion of a feather in honey. Given this, and the complex wind conditions to which the YTT was exposed, it seems implausible to model the YTT volume using a simple exponential decay of the ash thickness with distance from the source. Chapter four compares the chemical features of the YTT, investigating the differences between YTT preserved in different environmental contexts. Here the aim was the study of post- depositional leaching arising from environmental factors; however it was discovered that major variations are driven by the compositional stratification of the magma in the pre-eruptive reservoir. This is consistent with compositional zonation in the magma chamber, and highlights a strong correlation between time of eruption and composition of ash ejected. In the second part of the thesis new samples collected in the field were used to investigate the interactions between ash and receiving environment. Chapter five deals with the YTT deposits in the Son valley, India. Field investigations here indicate that hydrological processes such as lateral accretion and overbank floods removed and redeposited the ash several times after the eruption. This chapter discusses the consequences of such mechanisms for the application of the YTT as a chronostratigraphic marker for palaeoenvironmental and archaeological studies. 24 Chapter six discusses the characteristics of reworked tephra deposits, the differences between primary and secondary ash, and the mechanisms that underpin the accumulation and preservation of tephra. The sediments in the Lenggong valley, Malaysia, show that reworked deposits have variable textural and mineralogical features, and that such features can overlap with the characteristics considered unique to primary ash. The analyses suggest that the ash accumulated during a short period of time, thus implying that the possible impact of the YTT on local landscape lasted for a few decades. The evidenced depositional processes suggest that reworked tephra might not be suitable for palaeoenvironmental reconstruction. 1.6 Comments on the authorship of journal papers revised as chapters Chapters three, four, five and six of this thesis are based on manuscripts that have been submitted to journals for publication and involved co-authorship. I am first author of these works and the contributions from my co-authors went no further than typical levels of support from co- supervisors and colleagues, i.e. in the provision of comments and suggestions on early versions of the manuscripts. Specifically, Chapter 3 is the updated and revised version of the paper in press: Gatti, E., and Oppenheimer, C. 2012. “Utilization of distal tephra records for understanding climatic and environmental consequences of the Youngest Toba Tuff”. In: L. Giosan, D. Fuller, R. Flad, and P. Clift (Eds.), Climates, Past Landscapes and Civilizations, American Geophysical Union Monograph Series, Washington DC. I conducted all the analyses presented in this chapter, wrote the manuscript and drew the figures. Chapter four is based on the submitted article: Gatti, E., Achyuthan, H., Villa, I., Gibbard, P., and Oppenheimer, C. “Geochemical patterns in distal and proximal Toba glass”, Bulletin of Volcanology. I conducted all the analyses presented in the chapter, wrote the manuscript and drew the figures. Prof. Achyuthan assisted with the collection of the samples in India; Prof. Villa helped with the interpretation of the geochemical plots; my supervisors Phil Gibbard and Clive Oppenheimer revised the chapter. Chapter five is based on the published article: Gatti, E., Durant, A.J., Gibbard, P., Oppenheimer, C., (2011), “Youngest Toba Tuff in the Son Valley, India: a weak and discontinuous stratigraphic marker”, Quaternary Reviews, (30), 3925-3934. I collected the field analyses (see Chapter two), drew all the images and 25 wrote the manuscript. Dr. Durant assisted with the collection of data during the fieldwork and commented on the geological interpretations; Gibbard and Oppenhemeir commented on the draft of the manuscript. Chapter six is based on the published article: Gatti E., Mokhtar, S., Talib, K., Rashidi, A., Gibbard, P., Oppenheimer, C., “Depositional processes of reworked tephra: a case study from the Late Pleistocene Younger Toba Tuff deposits in the Lenggong Valley, Malaysia”, Quaternary Research. I collected the samples in Malaysia (see Chapter two), ran the analyses, wrote the manuscript and drew all the figures and tables. Prof. Mokhtar and Master students Kariunnisa Talib and Akin Rashidi helped with the field work in Malaysia, while Prof. Gibbard and Prof. Oppenheimer commented on the draft of the manuscript before submission. 27 Chapter 2. Research Methods This chapter briefly outlines the field and laboratory techniques that have been used in this study. It focuses on the sample preparation methods and technical procedures used in this thesis, rather than providing a detailed treatment of the principles behind each analytical technique (since these are long-established methods). Localities sampled during the fieldworks are summarised in paragraph 2.1. Further details of each site are given in the relevant chapters. Methods of data analyses (e.g. GIS-based) are also described in the appropriate chapters rather than in this section. 2.1 Field methods Six sites were investigated during two field campaigns in 2009 and 2010 in India, Malaysia and Indonesia (Figure 2-1 and Table 2-1). The samples of Toba ash presented in this work were collected by the author in each of these locations, except for the samples from Jwalapuram, in India (Chapters three and four), which were provided by Dr. Sacha Jones. Table 2-1 List of sites visited, with the corresponding analyses conducted. PS= Particle Size; MS= Magnetic Susceptibility; EPMA= Electron Probe Micro Analyser; LA-ICP-MS=Laser Ablation Inductively Coupled Plasma Mass Spectrometry. Site Field work Sample Collection PS MS EPMA LA-ICP-MS Jwalapuram (IN)      Son Valley (IN)   Bori (IN)      Morgaon (IN)      Lenggong (MYS)       Lake Toba (IND)   28 Figure 2- Figure 2- (Malaysia 1 Sites sample 2 The ash r ). d by the auth eported in c or for this wo hapter six w rk as collected from Kampung Luat, Le nggong valley 29 Samples were collected from fresh, clean surfaces and stored in plastic bags (Figure 2-2). They were then shipped to the UK for analysis (Table 2-1). Field mapping of the Son Valley (Chapter five) was conducted by the author with support from Dr. Adam Durant. Samples collected in the Son Valley did not reach the UK in time to be made available for the research. 2.2 Laboratory methods The following section outlines the procedures and techniques applied to the samples collected. Preliminary analyses were conducted using a scanning electron microscope (SEM) and associated energy-dispersive spectrometer (EDS) at the Department of Anatomy at the University of Cambridge. The author conducted all the analyses, except where specifically indicated. 2.2.1 Electron probe microanalyses Major and rare element geochemical fingerprinting is a routine procedure applied to determine the composition of volcanic ash and relate it to its volcano of origin (Westgate and Gorton, 1981; Stokes et al., 1992). Subsequent to preliminary analyses e.g. run to verify that the collected sediments were ash, the samples were chemically characterised, in order to compare them with verified YTT samples. The Electron Probe Micro-Analyser (EPMA) is a particle-beam analytical technique used to establish the composition of small areas on specimens. It can estimate major elements in areas as small as ~ 10 μm, making it suitable for geochemical analysis of small tephra particles. This technique uses a beam of accelerated electrons that is focused on the surface of the grain, producing characteristic x-rays. These x-rays are detected at particular wavelengths, and their intensities are measured to determine concentrations. Individual elements can be detected because each has a specific range of wavelengths that it emits. Samples were prepared for EPMA using 5% HCl and placed in an ultrasonic bath for 10 minutes to remove secondary carbonates. Samples in the fraction 63-125 μm were mounted, impregnated, polished and coated with carbon (Figure 2-3). Glass compositions were analysed in the Department of Earth Sciences, University of Cambridge on a Cameca SX-100 with one energy- dispersive and five wavelength-dispersive spectrometers. The accuracy was ± 1% for major elements, detection limits ranged from 1 to 20 ppm, and the spatial resolution was about 1 μm. A 30 beam curren at the begi excluding w Periclase (M provided by secondary a Figure 2- and polis of the gla 2.2.2 Las Trace eleme of the same necessary to YTT glasses a micro-ana with the se material, wh carrier gas. t of 15 keV nning to m ater. Inter g), Orthoc Sacha Jon nd backscat 3 Ash grains hed with diam ss. er ablation nt composi volcanic s verify that only. The l lytical tech nsitivity of ich is trans 2nA was ap inimise th nal standar lase (K), Ap es. The sca ter electron as they appe ond powder ICP-MS tion is valua ystem (We the sample aser ablatio nique that the ICP-M ported into plied to me e conseque ds were: Ja atite (P). T nning electr imaging sys ar under the in order to re ble for diffe stgate et al s collected w n ICP-MS ( combines th S. A pulsed the Ar pla asure Na, S nces of Na deite (Na), he secondar on microsc tem. EMPA camer move the sur rentiation o ., 1994; Pea ere YTT a Inductively e microme laser beam sma of the i, K, Ca, Ti, loss. The Diopside y standard ope (SEM) a. Grains we face impuritie f minor dif rce et al., 2 nd not OTT Coupled Pl ter-scale re is used to ICP-MS ins Fe, Al, Mg. analyses w (Si, Ca), Co used was sa used was e re mounted o s and expose ferences be 008a). In t and MTT asma Mass S solution of ablate a sm trument by Na was cou ere norma rundrum mple JLP3- quipped wi n epoxy resin the inner par tween erupt his case, it , and work pectromete the laser p all quantit a stream o nted lised (Al), 11s, th a t ions was with r) is robe y of f Ar 31 Trace element compositions of individual phases were measured using a New Wave UP213 Nd- YAG laser ablation system (an artificially grown Y-Al garnet doped with a small quantity of Nd) interfaced to a Perkin-Elmer Elan DRC II ICP-MS in the Department of Earth Sciences, University of Cambridge. Helium was used as the ablation gas, and was delivered to the sample ablation cell via a mass controller system (MKS Instruments, Cheshire, England). The helium flow rate was precisely controlled at 0.7 L min-1. The helium flow carrying the ablated sample material was joined with an argon stream from the ICP-MS at 0.8 L min-1 before entering the plasma. A 60 μm diameter laser beam, with a laser repetition rate of 10 Hz and laser power of ~ 0.2 mJ (8 Jcm-1) was used throughout the study. The spot size was chosen as a compromise between signal intensity and the size of the grains in the samples. The ICP-MS data acquisition settings were 1 sweep per reading, 80 readings, and 1 replicate; total data acquisition lasted 58 s. The first 20 s were gas blanked for each spot, and then put through laser analysis. There was a 45 s gas rinse out time after each spot to allow the element signals to return to baseline levels before moving to the next spot. The data were acquired at a rate of about one point per 0.7 s. The ICP-MS dwell times were selected on the basis of the isotope abundance and elemental concentration in the samples. For data processing and calculation of concentrations, Glitter Software (GEMOC, Australia) was used to process the raw data files. For all the data, NIST 610 trace elements in a glass matrix 3 mm wafer (National Institute of Standards and Technology, Gaithersburg, Maryland, USA) was used for calibration of element sensitivity. The certificate values of 500 ppm nominal for each element are not reliable, so instead the published and widely agreed values from Pearce et al. (1997) were used. The CaO (or for olivines, MgO) content of each sample was used for internal standard normalisation of the trace element signals. Calibration accuracy was verified by analysing NIST 612, 614, BCR-2G and T1-G (MPI DING standard, Mainz) as unknown samples and recoveries were typically 90-110% of the values in the GEOREM database. In addition, several analyses of the United States Geological Survey (USGS) standards BIR-1, BCR-2, BHVO-2 and were conducted during the study to verify calibration accuracy. These standards were analysed as glasses prepared from the rock powder available from USGS. Less than 10% ICP-MS drift was seen during the single day of measurements. 32 2.2.3 Malvern Mastersizer 2000 particle size analyser Characterisation of particle sizes of tephra deposits is vital to investigation of the methods of transport and sedimentation (Folk and Ward, 1957; Passega, 1964; Folk, 1966; McLaren, 1981), and to understanding the dynamics of post-deposition accumulation of the ash (Charman et al., 1995; Koniger and Stollhofen, 2001). Grains between 0.001 and 1000 μm were studied using laser diffraction, a technique that measures the intensity of light scattered as a laser beam passes through the dispersed sample. Samples were cleaned of secondary carbonates using 5% HCl and 10 minutes in an ultrasonic bath; 7% sodium pyrophosphate solution (Na2P2O7) was added to the solution to separate clay particles. All samples were centrifuged (3500 rpm for 13 min) to separate the supernatant, and thoroughly cleaned using deionised water. Laser-scatter analysis was conducted using a Malvern Mastersizer 2000 in the Department of Geography, University of Cambridge. The average from four analyses per sample was used. Grain-size statistics (Folk and Ward, 1957) were calculated using both the Malvern software SOP (Standard Operating Procedures) and GRADSTAT software, following Blott and Pye (2001). 2.2.4 Magnetic susceptibility The magnetic susceptibility indicates the degree of magnetisation of a material in response to an applied magnetic field. This technique was used to study the potential changes to tephra deposits during reworking. The magnetic susceptibility of the samples was measured using a Bartington magnetic susceptibility MS2 meter and MS2B dual frequency sensor in the Department of Geography, University of Cambridge. Cleaned bulk sediments were placed in 10 cm3 plastic pots, and samples were dried overnight in an oven (at 42°C). The data were acquired using Multisus software. The background magnetic field was measured before and after each sample reading in order to test for natural drift in the Earth’s magnetic field. The mass specific magnetic susceptibility of each sample (expressed in 10-8 m3 kg-1) was calculated by subtracting the mean of the two background measurements from the mean of the two sample measurements and dividing the resulting value by the dry mass of the sample. 33 Chapter 3. Particle size, thickness and volume of the YTT co-ignimbrite ashfall Based on Gatti and Oppenheimer (2012) Abstract Estimation of the volume of the co-ignimbrite fallout is a fundamental part of any estimate of the overall magnitude of the YTT eruption. To date, this quantity remains poorly characterised. This chapter presents particle sizes and thicknesses of distal YTT deposits from the literature and original work, in order to examine the variations of these parameters with distance from the vent. Thickness data are used to compare two techniques for volume calculation, the Pyle (1989) method, which estimates the volume by extrapolating the exponential thinning of the ash sheet with distance, and the Bonadonna and Houghton (2005) method, which applies a voronoi tessellation, calculating the volume by weighing the individual thickness measurements. After discussing volume estimation methods, I address analyses of particle size distributions. It is found that the median size of the finer particles shows no variation with distance, particularly beyond 1000 km from source. No ash deposits beyond 1000 km from the vent show exponential thinning decay in relation to the distance from the vent. Furthermore, the isopach map built from the available data shows that several wind systems affected the distribution of the tephra, and that for areas a distance > 2000 km from the vent the isopachs cannot be constructed because of lack of data. The study concludes that exponential models cannot be applied to the YTT ashfall. This chapter argues that without knowledge of the atmospheric conditions prevailing during the eruption no model can provide better than an order-of-magnitude estimate of the tephra fallout volume. It concludes that the voronoi is the fastest and simplest method of providing a first order estimate of the minimum volume. This approach yields a minimum amount of co-ignimbrite ash between 770 km3 and 2000 km3 (dense rock equivalent). 3.1 Introduction The impact of a pyroclastic eruption on terrestrial ecosystems depends heavily on the quantity and dispersal of ash that is erupted (Pollack et al., 1976). Estimating the volume of ash ejected is therefore a crucial goal when studying a co-ignimbrite eruption such as the YTT, which ejected vast quantities of fine ash. The essential concept behind the estimation of volume of ash is simple: samples of ash that are known to have come from a specific eruption (verified using geochemical 34 fingerprinting; Chapter four) are measured in terms of their geographical position and thickness at that point. It is possible to obtain a rough volume estimate by multiplying the average thickness of the observed deposits by the area covered by the sample sites. This, however, will be a crude estimate since the ash is never distributed uniformly. Effects of prevailing winds, sedimentation and air and sea currents will all act to deform the ash cloud, and the resulting distribution of the ash will therefore be highly non-uniform. The key question is 'Can we use knowledge about how ash disperses and measurement of ash size and thickness to improve on the crude volume estimate?'. Answering this question is the main aim of this chapter. There are, however, significant problems in applying standard volume calculations to the YTT co-ignimbrite deposit. For example, YTT deposits span the west through to the northeast quadrants around the caldera. They do not define a downwind area with clear elliptical isopachs, nor are they described by spherical isopachs, since ash has not been reported in the south and southeast of Sumatra. Other parameters such as the height of the eruptive column and the season of the eruption, which could constrain the model, are unknown. For these reasons, tephra volume estimates for large eruptions, and especially super-eruptions, have large errors (Self, 2006). This chapter first demonstrates that the distal YTT co-ignimbrite deposits are mostly composed of fine and ultrafine particles. It then shows that the size of the fine particles, beyond a threshold distance, no longer decreases exponentially with distance from the vent, and examines the implications of this behaviour for the thickness of the deposits. Finally, attempts to calculate the total volume of ash ejected using two methods and the results are discussed. 3.2 Methods of volume calculation in ignimbrite and co-ignimbrite eruptions Various methods have been developed to estimate ash volumes by using thickness from recovered distal ash. For example, Thorarinsson and Sigvaldason (1972) observed that tephra fall deposits from Hekla thinned exponentially with distance from the vent. Since then, several techniques have been applied to calculate volumes on the basis of exponential decay of ash thickness with distance. Pyle (1989a) developed this principle, formulating the volume (ܸ) as follows: ܸ = 13.08 ଴ܾܶ௧ଶ, where T0 and ܾ௧ are, respectively, the extrapolated maximum deposit thickness at th 1989 deca form ܶ = whe ܶ=t illus ash: ܸ = F c t w a v P t a Des been e vent and a). Extrapo y and an e ula: ଴ܶ ݁݌ݔሺെ݇ re ݎ= distan ephra thickn trated in Fig 13.08 ଴ܾܶ igure 3-1 Su ircular isopa hickness T a hich charac shfall in each olume is obt yle method hickness of th rising from u pite wide a shown to the distanc lation to a lliptical iso ݎ) ce from the ess at a cert ure 3-1. Th ௧ଶ mmary of Py ch area will h t the distance terises the di isopach is th ained by sum is expressed i e tephra she sing natural l pplication o display th e over whi n arbitrary pach distri vent, ݇ = ain ݎ distan e integratio le method (f ave an area o r depends o stance over w e thickness at ming (integra n terms of ha et decays by h ogs or logs of f the expon ickness var ch the thick thickness is bution. The ݈݊2 ܾ௧⁄ , ଴ܶ = ce from the n results in rom Pyle, 19 f ݀ܣ = 2ݎ݀ߨ n the thickne hich the thic that distance ting) over all lf-time decay alf. ܾ௧ is relat base 2. ential thin iations that ness of the possible a method p extrapolate vent. A sum the simplifie 89a). For a g . If we apply ss at the sou kness decrea , multiplied b isopachs at a length ܾ௧, w ed to the dec ning decay are more tephra she ssuming the resented by d maximum mary of th d equation iven distance an exponent rce ( ଴ܶ) and ses by a facto y the area of ll distances. T hich is the d ay length sim method, te complex th et decays by exponenti Pyle is ba (1) deposit th e Pyle meth for the total (2) from the ven ial decay equ the decay len r of e. The v each isopach. he decay len istance over w ply by a facto phra fall de an simple 35 half (Pyle al thickness sed on the ickness; od is volume of t ݎ, each ation, the gth (1/k), olume of The total gth in the hich the r of ln(2) posits have exponential , 36 thinning (Froggatt, 1982; Fierstein and Nathenson, 1992; Hildreth and Drake, 1992; Scasso et al., 1994). Rose (1993) argued that fine distal ash settlement differs from that of larger particles, thus volume calculations of some tephra deposits substantially underestimate the true values. Similarly, Bonadonna et al. (1998) and Bonadonna and Phillips (2003) noticed that major changes in thinning rates occur as the particle size decreases. This has been explained as a consequence of the changes of settling behaviours that occur when the particles decrease from high (> 500) to low (< 500) Reynolds numbers (Sparks et al., 1992). The Reynolds number is a dimensionless number that quantifies the relative importance of inertial and viscous forces for given flow conditions. It is expressed as ܴ = ்ఘ௅஗ where T is terminal velocity, ߩ and η the density and the viscosity, respectively, of the medium, and L the length of the particle. Terminal velocity T is reached when the drag force is equal to the gravitational force acting on the particle, so that ܶ is in general a function of particle density and size as well as fluid density and viscosity. Fine ash particles have low Reynolds numbers, which means that settling is dominated by the viscosity of the medium in which they are transported, while large particles characterised by high Reynolds number settle in more turbulent behaviour (in which the inertial forces of the fluid flow are dominant). Depending on the density of air, the boundary between low and high Reynolds number for ash particles occurs between ~ 500 to ~ 100 μm, shifting towards the coarser sized particles at higher altitudes due to decreasing air density (Alfano et al., 2011). The motion of fine particles (length <500 μm) is dominated by viscous forces and therefore strongly affected by the currents in the air (Ersoy et al., 2010). Indeed, Bonadonna et al., (1998) modelled the sedimentation from laterally spreading plumes and found that, beyond ~ 27 km from the vent, particles finer than 2000 μm are better predicted by using a power-law model rather than an exponentially decaying model. The power law function (ݕ = ݉ ݔ௕) allows the thickness (ݕ) to decrease more slowly as a function of increasing distance (ݔ), thus better describing the thinning rate of low Reynolds numbers particles. The method has been applied by Bonadonna and Houghton (2005) in a study of the volume of ash ejected by the Ruapehu eruption. The authors described a power law model (ܶ = ଴ܶ √ିܣ௞, cf. 37 Eq. (1)) and demonstrated that, in cases of eruption with a large amount of fine particles the exponential method can underestimate the total volume by a factor of at least two (Bonadonna and Houghton, 2005). Although these models are typically applied to plinian eruptions, in which ashfall is preserved in proximal areas and composed of lapilli and coarse ash (i.e. Bonadonna et al., 1998; Bonadonna and Houghton, 2005), the majority of volume calculations of co-ignimbrite ashfall have been made with the same methods. For example, the Campanian Ignimbrite (Pyle et al., 2006), the Minoan eruption (Pyle, 1989b), the 26.5 ka Oruanui eruption in New Zealand (Wilson, 2001), and the 1815 eruption of Tambora, Indonesia (Self et al., 1984) have been assessed with the Pyle (1989a) method. An alternative approach has been proposed by Perrotta and Scarpati (2003), who applied the Pyle (1989a) calculation to the Campanian Ignimbrite, but determined the areas of each isopach by measuring the areas enclosed within thickness contour lines, which were manually traced with drawing software. This avoided approximating the real shape with a simplified (circular of elliptical) shape. Yet, co-ignimbrite ashfall at much greater distances from the vent, and ashfall deposits are predominantly composed of fine and very fine particles (cf. Chapter one). The extreme case of the YTT introduces a high degree of uncertainty when discussing its co- ignimbrite volume with these methods. Rose and Chesner (1987) proposed a method explained in Rose et al. (1973), which plots the isopach thickness vs. the area within the isopach. The equation to calculate the volume was ܸ = ܣ׬ ሺݐ݀(ݐ , where ܸ = volume of ash, ܣ = area covered by a given thickness of ash, ݐ = the ash blanket thickness. They obtained a minimum volume of ~ 840 km3 Dense Rock Equivalent (DRE) (Rose and Chesner, 1987). The second and most recent attempt to calculate the volume of the YTT ashfall has been presented by Matthews et al. (2012). These authors presented a simulation to calculate the atmospheric dispersion and the thickness of the tephra (HAZMAP model from Macedonio et al., 2005). They obtained a total volume between 1500 and 1900 km3 DRE (Matthews et al., 2012). The detailed explanation of this method is provided in Macedonio et al., (2005). 38 3.3 Study methods The particle sizes and thickness data used for this study are listed in Table 3-1 and Table 3-2. Firstly, five continental ash samples collected during the 2009 and 2010 fieldwork were analysed for bulk particle-size distribution (Table 3-1). This was done in order to characterise the particle size of YTT distal deposits. Particle-size distributions were measured using a Malvern Instruments Mastersizer 2000 (§1.3 for description of the Malvern preparation and methods). Secondly, seven marine cores presenting two distinct coarse and fine grain units within the core (Table 3-1) were plotted on a size-vs.-distance graph, to study the distribution of coarse and fine particles in relation to the distance from the caldera. Thirdly, thicknesses at each location were retrieved from published work, my own fieldwork and personal communications from colleagues (Table 3-2). A database was prepared, showing the geographical coordinates and ash thickness for each data point. If the original work did not differentiate between primary and reworked units the point was excluded from the database. For this reason the thickness database of this chapter is much smaller than the geochemistry database presented in Chapter four. Table 3-1 YTT sites used for particle-size analyses Sample ID Latitude (degrees N) Longitude (degrees E) Mean diameter (wt%μm) Reference Terrestrial Bori 19.626 74.633 51 This study Jwalapuram 15.320 78.134 70 This study Morgaon 18.305 74.330 64.50 This study Son Valley 24.544 82.231 62.50 This study Tejpur 21.892 73.487 62 This study Marine Fine Coarse RC14-37 1.643 89.927 62 125 Ninkovich et al. (1978b) 28-KL 4.701 84.967 22 49.19 Kudrass (personal communication) 42-KL 9.925 84.812 15.63 55 Kudrass (personal communication) 45-KL 11.571 86.951 20.1 55.5 Kudrass (personal communication) 47-KL 11.831 88.851 31 88.39 Kudrass (personal communication) 51-KL 12.658 87.547 22.1 62.5 Kudrass (personal communication) 115-KL 17.7163 89.493 44 63 Kudrass (personal communication) 39 Table 3-2 Marine and terrestrial YTT cores reporting primary ash thickness. T= terrestrial site Sample ID Latitude (N) Longitude (E) Primary Thickness (cm) Reference CR-02 -3 82.25 8 Pattan et al. 1999 CR-05 -3 88 13 Pattan et al. 1999 NR-1 -9.93 77.7 10 Pattan et al. 1999 NR-21 -11.5 78.7 10 Pattan et al. 1999 NR-35 -11.93 78.483 12 Pattan et al. 1999 NR-54 -7 78.483 5 Pattan et al. 1999 SK-226 -13.3 75.483 8 Pattan et al. 1999 SS-657 -14 76 8 Pattan et al. 1999 MD972151 8.728 109.869 2 Song et al. 2000 SO90-93KL 23.588 64.216 3 Schulz et al. 2002 SO90-94KL 22.488 65.649 4 Schulz et al. 2002 SO93-115KL 18.075 89.380 6 Schulz et al. 2002 SO93-22KL 0.332 83.355 10 Gasparotto et al. 2000/ Kudrass (personal communication) SO93-9KL 2.927 80.388 4 Gasparotto et al. 2000/ Kudrass (personal communication) SO93-45KL 11.571 86.951 11 Gasparotto et al. 2000/ Kudrass (personal communication) SO93-47KL 11.831 88.851 10 Gasparotto et al. 2000/ Kudrass (personal communication) SO93-51KL 12.658 87.547 20 Gasparotto et al. 2000/ Kudrass (personal communication) SO93-119KL 17.095 87.7183 0 Gasparotto et al. 2000/ Kudrass (personal communication) SO93-115KL 17.716 89.493 6 Gasparotto et al. 2000/ Kudrass (personal communication) SO93-124KL 19.814 90.000 15 Gasparotto et al. 2000/ Kudrass (personal communication) SO93-126KL 19.823 90.441 2 Gasparotto et al. 2000/ Kudrass (personal communication) SO93-28KL 4.701 84.967 12 Gasparotto et al. 2000/ Kudrass (personal communication) SO93-29KL 5.5352 84.072 7 Gasparotto et al. 2000/ Kudrass (personal communication) SO93-1KL 7.858 79.130 1 Gasparotto et al. 2000/ Kudrass (personal communication) SO93-42KL 9.925 84.812 10 Gasparotto et al. 2000/ Kudrass (personal communication) ODP758(layer A) 5.384 90.361 34 Dehn et al. 1991 MD01-2393 10.502 110.061 4 Liu et al. 2006 17962-4 7.181 112.081 3.5 Bühring et al. 2000 17961-2 8.506 112.331 2.5 Bühring et al. 2000 RC17-145 6.702 96.647 4 (Ninkovich et al., 1978a; 1978b; 1979) V29-14 6.857 86.225 7 (Ninkovich et al., 1978a; 1978b; 1979) V19-176 7.071 76.754 2 (Ninkovich et al., 1978a; 1978b; 1979) RC17-128 3.078 80.135 9 (Ninkovich et al., 1978a; 1978b; 1979) V29-31 3.264 78.018 3 (Ninkovich et al., 1978a; 1978b; 1979) V19-175 3.896 80.520 11 (Ninkovich et al., 1978a; 1978b; 1979) RC17-132 1.080 85.083 2 (Ninkovich et al., 1978a; 1978b; 1979) RC14-37 1.643 89.927 15 (Ninkovich et al., 1978a; 1978b; 1979) V29-15 11.982 88.678 3 (Ninkovich et al., 1978a; 1978b; 1979) 40 RC12-340 12.880 90.278 12 (Ninkovich et al., 1978a; 1978b; 1979) RC12-341 13.266 89.586 11 (Ninkovich et al., 1978a; 1978b; 1979) V29-23 4.356 79.513 9 (Ninkovich et al., 1978a; 1978b; 1979) V29-24 4.737 79.028 10 (Ninkovich et al., 1978a; 1978b; 1979) RC12-343 14.960 90.850 8 (Ninkovich et al., 1978a; 1978b; 1979) SO93-126KL 19.973 90.033 2 Kudrass et al. 2001 1143-A 9.359 113.290 2 Liang et al. 2001 JWP3 (T) 15.320 78.134 4 Petraglia et al 2007 Serdang (T) 3.0136 101.709 85 Chesner et al. 1991 Son Valley (T) 24.544 82.231 5 This work Two volume-calculation techniques are developed. The first is based on an exponential dependence between thickness and distance from the vent (Pyle, 1989). Isopach areas (areas of the same thickness) were extrapolated and plotted against the thicknesses in a ln (thickness) vs. (isopach area)1/2 plot (Figure 3-2). The total volume of an exponentially thinning tephra sheet is calculated with Eq. (2). The parameters ଴ܶ (maximum thickness at the vent), ܾ ௧ and ݇ are extracted from Figure 3-2. ଴ܶ is the first number in the equation describing the exponential decay fit (Figure 3-2), ݇ is the slope on the ln (thickness) - (isopach area)1/2 plot and the rate of thinning is calculated with the formula ܾ ௧ = ݈݊2 ݇⁄ (Figure 3-1). The extrapolated parameters ଴ܶ and ܾ ௧ and the resulting volume are listed in Table 3-3. Table 3-3 Minimum and maximum volume of ash-fall estimated assuming exponential thinning of the tephra sheet. Dense rock equivalent values are obtained from bulk volume multiplied by a factor of 0.5 (Rose and Chesner, 1987). Minimum Maximum Area (km2) 13 × 106 (polygon) 24 × 106 (rectangle) ଴ܶ (cm) 106 223 ܾ௧ (km) 391 614 Volume (km3 DRE) 1208 5000 F b a t t Isop (GIS to o sem spat resu but data inte data in th igure 3-2 Ln een calculate set of input hicknesses re hat result fro ach areas w ). Kriging i ne anothe ivariogram ial auto-cor lting isopac also with th points. A rpolation w points tow is region. (thickness) - d using krigin points assigne ported in the m the 55 data ere extrapo s an interpo r are mor shows that relation. T h map is sh e direction n anisotrop as not able t ards the Sou isopach area g statistical a d by the auth literature (Ta points. lated using lation techn e alike tha towards 342 he model t own in Fig (anisotropy y correcti o define clo theast of th ½ plot using pproximation or. The thick ble 3-4). The a kriging t ique based n those fu degrees N herefore de ure 3-3. Sev ). Wind is on was the sed isopach e vent and the Pyle (198 . The metho ness surface i twelve data p echnique in on spatial au rther away -NW the m forms isopa eral data ch the typical refore app s (Figure 3- so insufficie 9a) method. T d calculates a s calculated u oints shown Geographi tocorrelatio from eac ajority of th chs in the anged not cause of an lied to the 3). This ari nt data to e he isopach a statistical sur sing 55 prima are the twelve cal Informa n (things th h other). T e data hav N-NW dir only with t isotropy wit model. N ses from the xtrapolate t 41 reas have face from ry ashfall isopachs tion System at are close he kriging e a medium ection. The he distance hin a set of otably, the re being no he isopachs , 42 Figure 3- precludes area with which is data. The second is defined a associated w et al., 1983) on Delauna thickness fo Both the vo area), defin (maximum maximum a area that ca 24 × 106 km minimum v 3 Isopach ma fitting a pre measuremen a calculated technique a s the partiti ith a partic . The tephra y triangulat r the weigh lume techni ed by the area) deter rea the “mi n bound all 3. Finally, I olume eject p of the YTT cise shape fo ts, while the surface based pplies a vor oning of th ular data po thickness d ion. The to ted area of ques were c extent of t mined by t nimum-bou the data. Th also applie ed. thickness. Th r the thicknes maximum a on the mini onoi tessell e plane suc int contain ata were tra tal thicknes each Voro alculated us he availabl he statistic nding recta e polygona d a crude A e absence of s distribution rea is defined mum rectang ation, a well h that, for s all spatial nsformed in s volume w noi cell (V= ing two are e field data al calculatio ngle”, since l area is 13 rea × aver cores in the s . The minim as the ‘mini ular extent d -known me any set of d locations cl voronoi ce as calculate Σ Polygon as: a smaller only; and n itself (Fi it represent × 106 km2, w age thickne outheaster pa um area incl mum-boundi efinable with thod of spat istinct data osest to tha lls with an d by summ area × Polyg polygonal a larger r gure 3-3). s the minim hile the rec ss calculatio rt of Sumatra udes only the ng rectangle’ the available ial analysis points, the t point (Go algorithm b ing the ave onaveraged thick area (minim ectangular GIS names um rectang tangular ar n, to assess , that cell wda ased rage ness). um area the ular ea is the 3.4 3.4 Bulk distr incl F p f w Plot relat the ash Results .1 Size cha particle-si ibution. Al uding signif igure 3-4 Pa article size i inest ash < 3 ithin the cat s A and B in ion to the d vent, with r units show a racteristic ze analyses l particles icant fractio rticle-size com s between 62 2 μm. The sh egory of low R Figure 3-6 istance from egression c weak expo s of distal indicate tha at distal loc ns of fine (< position of and 88 μm. arp cut off at eynolds num compare th vent. The oefficient (R nential deca fallout t the YTT t alities in th 63 μm) an YTT ash fallo The right ske 1000 μm sho bers particles e coarse an coarse laye 2) of = 0.6. y as a funct ephra is tex e selected d very-fine ( ut from five wness of the ws that the Y . Tejpur samp d fine grain rs show exp By contras ion of distan turally fine cores are < < 32 μm) as terrestrial sit distribution TT terrestria le provided b -sizes of th onential de t, the fine p ce (R2= 0.4 sand, with 1000 μm i h (Figure 3 es in India. T indicates a lo l distal depos y Raj (Raj, 20 e seven mar cay with di articles from ). 43 a unimodal n diameter -4). he mean ng tail of its all fall 07) ine cores in stance from the upper , 44 Figure 3- exponent while the distance t over whic forces and 3.4.2 Thic In order to available ma the caldera thinning, w Figure 3-7sh Matthews e (Figure 3-2) DRE, for th 5 Plots of the ial equation i equation in ravelled. Sam h the finest p settling beha kness varia study the r rine and ter (Figure 3-6 hile the m ows the tw t al. (2012). . The total v e polygonal coarsest (A) n A) is eviden B) demonst ples 115-KL i articles, char viour. tions and elation betw restrial YTT ). Only the ajority of t o volume c The thickn olume calc and rectang and finest (B ce for a high rates a weak n graph B) al acterised by l volume een the ash reporting ash deposit he distal te alculations o ess ଴ܶwas e ulated with ular area re ) average pa correlation be er correlation so suggest tha ow Reynolds thickness primary ash s within 100 phra thickn f this study xtrapolated Eq. (2) resu spectively ( rticle sizes (v tween coarse (R2= 0.4) b t beyond ~ 2 numbers, are and the dist were plotte 0 km from esses are u and comp using the l lted in ~ 12 Figure 3-7a) olume %) vs. ash and dista etween fines 000 km a thr governed by ance from d against th the vent sh ncorrelated are them wi og (ܶ) vs. l 00 km3 DR . The volum distance. The nce (R2= 0.6) t particles vs eshold occurs different drag the vent, all e distance f ow expone with dista th the mod og (Area½) E and 5000 e calculated , . , the rom ntial nce. el of plot km3 on the yield The 2000 km3 al. ( F a d s i d p smaller are ed a volum voronoi tec km3 DRE. minimum 2012) (Figur igure 3-6 Th nd bioturbat ashed black egmentation s formed from eposition of article popul a is in acco e of 1500 km hnique (Fi This estima volume (Ro e 3-7c). ickness versu ed layers (wh line shows t into three do deposition low Reynold ations). In the rdance with 3. gure 3-7b) i te is consist se and Che s distance fo en indicated) he generalise mains as desc of high Reyn s number par case of Toba the mode ndicates a n ent with bo sner, 1987), r terrestrial a were not inc d model for ribed by Bon olds number ticles (while , the proxima l presented ew ash vol th Rose and and the mo nd deep-sea t luded in the thickness va adonna et al. particles, and the transition l sites are at 3 by Matthe ume betwee Chesner’s re recent e ephra layers. volume calcu riations in te (1998), where the distal se al region ha 90 km from t ws et al. (2 n 770 km3 original esti stimate by M Reworked th lation (Table phra fall dep the proxima gment is form s a mixture o he source. 45 012), which DRE and ~ mate of 800 atthews et icknesses 3-2). The osit with l segment ed from f the two 46 Figure 3- and (B) V thickness (2012). 7 Thickness m oronoi tesse value, weigh ap obtained llation. Aver ted by the ar using (A) exp age thickness ea of each vo onential deca es values we ronoi cell. ( y of thickness re calculated C) The isopa (expressed in on the basis ch map in M cm intervals of the single atthews et al ) . 47 3.5 Discussion 3.5.1 Distribution of YTT co-ignimbrite ash as a function of particle size Figure 3-4 shows that the majority of the YTT distal deposits are composed of fine to very fine ash. Figure 3-5 shows that the finer mode shows no variation in diameter with distance from source. Below 100 μm, a particle’s terminal velocity depends highly on size of the particle and viscosity of the medium (Rose, 1993). In fact terminal velocity in this viscous-dominated regime depends on the square of the particle size, meaning smaller particles fall much more slowly (Wilson and Huang, 1979; Ersoy et al. 2006). In consequence, they spend more time suspended in the atmosphere and therefore have more time to be influenced by the complex currents in the atmosphere (Delmelle et al., 2005), which will increase the anisotropic nature of their distribution. Although the closest marine core (ODP) is indeed negatively correlated with distance (all cores further away have a lower thickness) all the other marine cores, all lying further than 1000 km from the source, show no correlation with distance. Clearly, a single point is not enough to determine whether there is effectively a correlation, and certainly not enough to determine the nature of this correlation (e.g. exponential vs. power law). The absence of a clear relationship between distance and thickness, particularly at large distances, is important and, in addition to the plausible argument given above, based on the finer ash’s being dominated by viscous flow, other authors have speculated on the mechanisms that produce an increasing anisotropic distribution with distance from the source. Sparks and Huang (1980) interpreted this as evidence of two volcanic clouds (cf. Chapter one, Figure 1-4). They suggested that in proximal areas, both the fine and the coarse mode arose from the development of a Plinian column, which deposited both coarse and fine ash from a single- column developed around the vent. The distal deposits were, rather, generated in the co- ignimbrite cloud, much finer and able to be transported further away. Another explanation might lie in the wind action upon the co-ignimbrite cloud. Both proximal and distal deposits could have been generated in the co-ignimbrite cloud, but at major distance the local winds break up the co- 48 ignimbrite cloud and spread fine in different directions, generating the anisotropic effect observed in the database. 3.5.2 Wind patterns Figure 3-6 shows that at proximal sites, the thickness decays with increasing distance from the vent, whereas beyond ~ 1000 km the thickness shows no correlation. The isopach areas used to calculate the total volume with the Pyle formula (Eq. (2)) do not resemble an elliptical or circular shape, because of the complex wind systems that affected the distribution of the tephra, and isopachs in ultra-distal deposits could not be constructed (Figure 3-3). Outcrops in ultra-distal areas (> 2000 km) are in fact too scarce to produce a robust statistical approximation with kriging (Rose and Durant, 2009). Overall, the data suggest that the exponential model, which considers a homogeneous wind profile, is inadequate to determination of ash dispersal in ultra-regions when there are complex wind patterns present. A recent study used a three-dimensional simulation to determine the Campanian Ignimbrite tephra dispersal (Costa et al., 2012). The study was based on a set of fully time-dependent meteorological fields and a range of parameters such as erupted mass, mass eruption rate, column height, and total grain size distribution extrapolated from tephra cores in ultra-distal regions (up to 2500 km from the source). The approach was different from that of the study of Matthews et al. (2012): the Costa et al. (2012) simulation uses sets of different wind directions and climate conditions to describe the different ash thickness patterns observed in the real data. Instead Matthews et al. (2012) applied two static wind directions (N-NW and E wind) to describe the entire thickness distribution. The study finds that distal dispersal of co-ignimbrite ashfall cannot be modelled using isopach-based approximations. The simulation indicated 250– 300 km3 of total volume of tephra for the Campanian Ignimbrite, two orders of magnitude larger than the previous estimation suggested in Pyle et al. (2006). 3.5.3 Validity of volume models applied to the YTT An accurate estimation of tephra volumes from deposit thinning in ultra-distal regions with traditional calculation is almost impossible. Given that the ultra-distal deposits are the chief 49 constituents of the co-ignimbrite ashfall (Figure 3-4), and exponential decay models fit neither the particle size nor the thickness distributions of ultra-distal ashfall deposits (Figure 3-5, Figure 3-6), it follows that the most important parameter to calculate the volume of the YTT co- ignimbrite ashfall is poorly constrained. In the absence of a better understanding of how much ultra-distal ash was ejected, any volume estimate will to have large error bands. This is clear in the results presented in Table 3-4: all the calculations have a large degree of uncertainty. The models can provide a good approximation for the more proximal deposits decaying with an exponential thickness, but they cannot describe the distal and ultra-distal thickness. This indicates two major conclusions: 1) at present, no model can provide better than an order-of-magnitude estimate of the tephra fallout volume; 2) from the foregoing conclusion, it seems unnecessary to apply exponential calculations or standard wind simulations. This is because they cannot both account for the fundamental, distinguishing features of the YTT ashfall: there is not a unique wind pattern, nor is there an exponential decline of the tephra thickness with distance. Since all the methods presented both in this chapter and the literature are only crude estimations of the minimum volume, the choice of the voronoi tessellation appears the more suitable to constrain a simplified calculation of the volume of the ashfall. This is because it is more straightforward than both the exponential method and the computer simulation of Matthews et al. (2012). The values (770 –2000 km3) overlap with the value of 800 km3 suggested by Rose and Chesner (1987) and the most recent model by Matthews et al. (2012). Nevertheless, it is important to emphasise that the technique is not a model of tephra dispersal, but rather a statistical calculation that weights the individual samples. The results should therefore be interpreted considering some limits of the database, including the scarcity of data points and uneven data-point distribution. For example, Malaysian sites preserve an average thickness between 18 and 25 cm thick of the YTT, but this is potentially biased by inclusion of the Serdang ash (Stauffer et al., 1980), near Kuala Lumpur (Malaysia), reported to be 85 cm thick. Similarly, the absence of thickness information between Malaysia and the South China Sea influences the reliability of the thickness approximation of the inland values in the eastern sites. Another issue with the database is the possible overestimation of ash thickness, particularly in terrestrial sites subjected to significant post-depositional reworking. 50 In addition, the voronoi tessellation can be executed in GIS only within a projected coordinate system, thus introducing an area error when transforming the sphericity of the Earth to a flat plane. The error increases with the increase of the area, and this could account for overestimation of the rectangular-area volume. Finally, the polygonal-area volume obtained with the voronoi tessellation (770 km3) is almost half the value estimated by Matthews et al. (2012). However, these authors reported an overestimation of the modelled thicknesses of between 0.2 and 5 times the observed data that could account for these differences. Table 3-4 summarises the range of published measurements, together with this study estimates of the total erupted ash (dense rock equivalent) volume. In view of the results discussed above, all the calculations presented and discussed in this work should be used only as indication of minimum volume. Table 3-4 Comparison of volume approximation models. Volume calculation technique Volume km3 (DRE) (polygonal area) Volume km3 (DRE) (rectangular area) Exponential decay 1200 5000 Voronoi 770 2000 Simple approximation (Total Area × 10 cm average thickness) 650 1200 Simulation (Matthews et al., 2012) 1500 1900 Exponential (Rose and Chesner, 1987) 800 / 3.6 Conclusion Since the end of the 1980s, several YTT ash deposits have been discovered in the Asian continent. A re-analysis of the YTT tephra deposits and an update of the current data were therefore timely. From the particle-size distributions of seven marine cores it is observed that the coarse mode decreases in median diameter with distance from the source, whereas the finer mode shows no variation. This demonstrates that the characteristics of the fine particles strongly influenced the dispersal patterns and accumulation of the YTT ashfall deposits. Moreover, beyond ~ 1000 km, neither coarse nor fine particles are well characterised by an exponentially thinning model. This is likely due to winds having made the distribution highly anisotropic and introduced multiple directions of distribution. 51 Particle-size behaviour is reflected in the thinning rate of the ash sheet. Ashfall deposits beyond 1000 km from the vent show no exponential thinning decay in relation to the distance. This suggests that volume calculations based on exponential decay of thickness cannot be applied to the YTT. Moreover, the isopach map, necessary to application of the exponential method, cannot be properly traced, because of lack of data in extreme distal areas and because of the complex wind systems affecting the distribution of the tephra. It follows that volume calculations based on single wind directions (i.e. exponential and power-law models) cannot properly account for the YTT dispersal and volume, and that any volume estimation based on isopachs should be avoided. The most reliable statistical interpolation to assess a simplified value of the minimal volume of ash ejected is the voronoi tessellation, which indicates a total volume ejected between 770 km3 (DRE) and 2000 km3 (DRE). These data correspond with the first estimates provided by Rose and Chesner (1987) and the most recent values provided by Matthews et al. (2012). In order to provide an accurate approximation of the total volume of ash ejected during the YTT eruption, more complex simulations accounting for the issues identified above should be proposed. An example is the recent three-dimensional simulation applied to the Campanian Ignimbrite distal deposits. A foreseen issue is that the YTT database is much less comprehensive than that for the Campanian Ignimbrite, but larger in terms of aerial distribution (the Campanian Ignimbrite tephra have been recovered at a maximum distance of 2500 km from the source, while the YTT ashfall mantle extend to ca. 4000 km). It is necessary to investigate further the presence of YTT ash in marine sediment cores beyond southern Sumatra. At present the complete lack of data does not support the creation of a statistical surface correctly describing the YTT ashfall thickness. Several ODP sites in the southern and eastern part of Sumatra report the occurrence of Late Pleistocene ash layers (ODP 115 in the Indian Ocean south of Sumatra and ODP leg 117 in the southern part of the China Sea). New geochemical investigation of these cores might provide the data points necessary to establish the southerly distribution of the YTT ashfall sheet. The next chapter analyses in detail the chemical features of 72 established YTT marine and continental sites. Geochemical fingerprinting represents the bridge between studying the YTT as 52 a volcanic entity and as sediment, since the geochemical composition of the glass needs to be assessed before proceeding to correlate tephra over greater distances. 53 Chapter 4. Geochemical patterns in proximal and distal Toba glass Based on Gatti et al. (submitted paper) Abstract This chapter will focus on its chemical properties, synthesising all readily available geochemical data on glass compositions of the YTT. The study includes 69 analyses drawn from the literature and three new analyses. The dataset shows considerable chemical variation. Three principal sources of variation were identified: (i) compositional zonation of the magma reservoir (ii) post-depositional alteration, and (iii) methodological biases. The principal findings are that: (i) the YTT glass geochemistry at a given site strongly reflects the stage of the eruption that yielded the sample (ii) post-depositional glass alteration in marine environments is related to site-specific pore water chemistry (iii) all the samples show a minor ‘laboratory fingerprint’. 4.1 Introduction The YTT has been correlated geochemically through marine and continental deposits as far as 4000 km from Sumatra (Schulz et al., 2002). The YTT deposits have been identified and characterised geochemically for over 100 sites in southern and south-eastern Asia (Figure 4-1). Characterisation of major element geochemistry using an electron microprobe provides reliable results when applied to single glass shards (Westgate et al., 1994; Pearce et al., 2008b). The geochemistry of the YTT glass was assessed (Chesner, 1988) and used for distal stratigraphic correlations and dating (e.g. Horn et al., 1993). Westgate et al. (1998) concluded from the geochemical association that all the ash sites on the Indian subcontinent belong to the YTT. However, other studies have argued against this view and have proposed that the YTT is not the exclusive ash-fall distributed in India. 54 Figure 4 geochemi detailed t recognise work on t Westaway e western Ind India belon element fin eruptions a Morgaon n other ash as succeed in variations. provide an i -1 Geographi cally fingerp han the thick a tephra stra he YTT prese t al. (2011) ia (~ 809 k g to the Ol gerprinting re geochem or that from signed to th showing the Such variat ndication o cal distributi rinted (Table ness and parti tum, geochem nts complete obtained a a and ~ 714 dest Toba T has not r ically simila Bori show e YTT (Sha difference ions reflect f which eru on of the Y 4-2). Note cle-size datab ical fingerpri major compo significant ka respect uff (OTT, esolved this r (Smith et s significan ne et al., 19 s between a chemical ption gener TT. The dot that the geoc ase (Chapter nts are a com nents analyse ly older age ively) and s dated 840 issue sinc al., 2011; L t major ele 95; Westgat sh grains is stratificatio ated the ash s represent hemical data 3, Table 3-2) pulsory proc s. for the ash uggested th ± 30 ka) ra e all three ee et al., 2 ment differe e et al., 199 to charact n in the m ), and post- YTT sites th base of the . This is becau edure, thus ev at Morga at some tep ther than t of the mo 004). Neith nces when 8). An appr erise the YT agma reser depositiona at have been YTT is more se in order to ery published on and Bor hra deposit he YTT. M st recent T er the ash f compared w oach that co T geochem voir (and l alteration. i, in s in ajor oba rom ith uld ical thus For 55 example, specific leaching processes, such as hydration (Noble et al., 1967; Cerling et al., 1985; Ghiara and Petti, 1995), or desilication (Wada, 1987; Bakker et al., 1996), give rise to alkali and SiO2 removal, processes that can perturb K-Ar systematics, resulting in discrepant K-Ar ages (Cerling et al., 1985). Lastly, inter-laboratory reproducibility of chemical analyses should also be assessed in order to quantify possible biases that could result in apparent chemical differences. Despite the significance that secondary chemical effects can have for the assessment of the distribution and age of the YTT, this issue has hitherto received little attention. The key questions include how much variation exists in distal YTT glass analyses and what the origins are of such variations. To address these questions and to identify pre-eruptive versus post-eruptive variability, all readily available YTT glass geochemical data were compared. Specifically, the variations reflecting analytical bias, magmatic differentiation or post-depositional alteration are addressed. 4.2 Geochemistry of the YTT Ninkovich et al. (1978a) carried out the first characterisation of the Toba tephra from marine cores recovered from the Bay of Bengal. More recently, Chesner, (1998) provided an extensive overview of the YTT ‘super eruption’ and its occurrence in regional context. Chesner (1998) described the YTT as sourced from a compositionally zoned silicic magma (Figure 4-2). Compositional zonation typically results from crystal fractionation. Crystallisation begins in the lower parts of the magma chamber, either on the walls or in the magma itself. The first minerals that crystallise (as temperature falls) are ferromagnesian (‘mafic’) compounds with low silica content, such as olivine and clinopyroxene. As the crystals form, the magma becomes depleted in Fe and Mg, SiO2 enriched, and less dense. This more ‘evolved’ magma is buoyant and tends to rise to the roof zone. The continuous re-equilibration between melt and crystals leads to the formation of successive batches of evolved, SiO2-rich liquids. These stratify at different levels according to their density. The result is a stratified cap of evolved magma, underlain by a pool of more mafic residual magma (Figure 4-2). 56 The bulk c classified th the YTT fal pumices) in with SiO2 c (Marel, 194 composition stratified m Recent stud 4.0–5.5 wt% The Toba g Smith et al remains sim This chapte ratios rathe variations, w Figure 4- chamber. omposition e rocks as ‘h ls within th dicated that ontent typi 8). In acco ally zoned, agma chamb ies on YTT H2O, < 100 lass compo ., 2011), an ilar (Chesn r will demo r than with hich reflect 2 Schematic Modified fro of the YTT igh-SiO2’ ( e high-SiO the glass m cally exceed rdance wit the majorit er (Figure 4 crystal-hos ppm CO2, sitions are d even wh er, 1998). nstrate that traditiona the magma representatio m Chesner, 1 rocks ran > 73% SiO2 2 category ( atrix compo ing 76%. T h Chesner’s y of the YTT -2). ted glass in < 2000 ppm almost eute ere crystall if these gla l Harker di tic source a n of the hy 998. ges from r ) and ‘low-S Chesner, 19 sition is m his classifie (1998) hy erupted m clusions su Cl and < 3 ctic (i.e. mi isation exte sses are com agrams, the nd preserva pothesised m hyolite to r iO2’ (68–72 98). Analys ore evolved s the YTT pothesis th agma was s ggest pre-e 2 ppm of S nimum mel nt varies t pared on glass geoc tion pattern agmatic zona hyodacite. % SiO2). Th es of glass than the bu glass separ at the mag tored in the ruptive vola (Chesner a ts in the Q he compos the basis of hemistry sh s of individ tion in the Chesner (1 ree-quarter separates (f lk composit ates as rhy ma chambe upper part tile content nd Luhr, 20 -Ab-Or sys ition of gla their eleme ows impor ual glass sha Toba magma 998) s of rom ion, olite r is of a s of 10). tem, sses ntal tant rds. 4.3 Seve from 4-1 Mor (Tab focu Wes poli F w Tabl Labo were wt% SiO2 Al2O3 TiO2 FeOto MnO MgO CaO Na2O K2O n Total Methods nty-two YT the literat and listed i gaon (Figu le 4-1). The s of discuss taway et a shed and co igure 4-3 YT ere analysed e 4-1 Samples ratories of Ea also recalcula Morga Kadhi r 73.9 (1 11.80 (0 0.04 (0 t 0.85 (0 0.04(0 0.06 (0 0.76 (0 3.17 (0 5.01 (0 14 95.7 T geochem ure (Table 4 n Table 4-2 re 4-3a), Bo Morgaon a ion because l., 2011). S ated with go T ash in cont to assess the used as cont rth Science a ted to 100% ( on Mo iver Norm .16) 7 .29) 1 .05) 0 .34) 0 .08) 0 .05) 0 .09) 0 .2) 3 .40) 5 3 10 ical analyses -2, at the en . The geoch ri (Figure 4 sh has not it has pro amples wer ld (§ 2.2 fo inental enviro accuracy and rols in this ge t the Univers normalized) rgaon alized K 7.26 7 2.34 1 .05 0 .89 0 .05 0 .07 0 .79 .31 3 .24 0.00 were comp d of the ch emistry of t -3b) and Jw been geoche vided an en e prepared r description nments. Sam reproducibili ochemical stu ity of Cambr for comparati Bori ukdi River 3.09 (1.10) 1.57 (0.29) .053(0.05) .84 (0.33) .05 (0.08) .067 (0.05) 0.76(0.10) .127(0.20) 4.84(0.36) 14 94.54 iled and co apter). The hree sample alapuram s mically cha igmatic dat for EPMA of EPMA m ples from a) M ty of the comp dy. The geoc idge. Standar ve purposes. Bori Normalized 77.31 12.24 0.06 0.89 0.05 0.07 0.81 3.31 5.12 99.86 mpared, 69 sites review s of possib ite 3 (Figur racterised b e of ~ 800 analyses, m ethods). orgaon, b) B ositional ana hemical analy d deviations g JWP Jwalapur Jurrer 74.24 11.75 0.05 0.84 0.08 0.05 0.69 3.23 4.90 1 95 of which we ed are show le YTT ash e 4-3c), are efore, altho ka (Mishra ounted, im ori and c) Jw lyses. ses were carr iven in brack 3-11S am site 3, u valley (1.16) (0.29) (0.05) (0.34) (0.08) (0.05) (0.09) (0.20) (0.39) 5 .83 57 re obtained n in Figure origin from also shown ugh it is the et al., 2009 pregnated alapuram ied out in the ets. The data JWP3-11S Normalized 77.47 12.26 0.05 0.88 0.08 0.05 0.73 3.37 5.11 100.00 ; , 58 4.4 Result 4.4.1 Anal In order t concentratio The sample sources (Ta site 3 (JWP) the sample 4) reported to the same Figure 4-4 In several labora The samples o 4.4.2 Mag Magmatic secondary a Zr, Y, Nb immobile el s ytical bias o quantify ns was plot s overlap w ble 4-3). Th reported b analysed by by Westgat samples ana ter-laboratory tories; pairs a verlap within matic diffe differentiati lteration pr and Al2O3. ements are inter-labo ted for iden ithin the us e SiO2 and y Petraglia e Smith et al. e et al. (199 lysed by Sh reproducibil re highlighted the stated un rentiation on can be ocesses (Flo Characteri not prone t ratory repr tical sample ually assum Al2O3 conce t al. (2007) (2001). Ind 8) show low ane et al. (1 ity. The grap by a dashed certainty of 1 distinguis yd and Wi sed by inso o mobilisati oducibility, s reported i ed uncertai ntrations fo and re-anal ian and Ma er Al2O3 co 995). h shows four line joining th %. hed using nchester, 19 lubility in on during r the variab n the literat nty of ± 1 % r the samp ysed here, a laysian sam ncentration pairs and on e same symb elements t 78). Immob hydrous fl ecrystallisat ility of S ure (Table 4 given from le collected re 0.2% low ples (filled s (by ca. 0.5 e triplet of sa ols, colour-co hat are im ile elemen uids at low ion. They th iO2 and A -2). the publis on Jwalapu er than thos circles in Fi %) with res mples analys ded by labora mobile du ts include T temperatu erefore pro l2O3 hed ram e of g. 4- pect ed in tory. ring iO2, res, vide a re disti inco frac char indi Figu and and glas Figu The samp Beca vari liable indica nguishing m rporated in tional cryst acteristic m cation of th re 4-5 show distal tephr Al2O3/TiO2 ses. re 4-5 Immob differences a les of Gaspar use the YT ations are c tor of magm agmatic d ilmenite an allisation a afic elemen e variation o s the FeO/ a deposits. ratios, and ile element r re substantial otto et al. (20 T was sour orrelated w atic comp ifferentiatio d rutile. Si nd not sub t incorpora f mafic con TiO2 v. Al2O The graph an order o atios of YTT and unrelate 00) are not pl ced from a ith the strat osition. In t n. Al is inc nce both Al sequently ted in olivi tent in the m 3/TiO2 rati shows linea f magnitud glasses from d to range o otted, because zoned mag ification of his case FeO orporated i and Ti are modified b ne, thus the agma. os extracted r correlatio e variation distal ash and r bearing of s no TiO2 con ma chambe the pre-eru , TiO2 and n feldspars immobile, y secondar FeO/TiO2 from YTT n (R= 0.93) in the mat proximal pu ites from To centrations w r, it is poss ptive magm Al2O3 were and garnet, their ratio i y alteration ratio provid glasses fro between th rix compos mices deposit ba. The Bay ere reported. ible to test a. This hyp 59 selected for while Ti is s set during . FeO is a es a robust m proximal e FeO/TiO2 ition of the s in Sumatra of Bengal ash whether the othesis was . 60 tested by loc 4-6) on Figu the stratigra 2017b, from suggests tha time a given immobile el the 18 ocea did not repo Figure 4- 4.4.3 Post Ash units ca vary accord or deltaic) a etc; see cha tephra sequ Such accum catchment (Kataoka et the ash laye ating analo re 4-5 (sam phically low the upper t the chemi portion of ements, the nic core sam rt TiO2 con 6 Stratigraphy -deposition n be preser ing to the r nd the sedim pter six). W ences that c ulations ca areas, or fro al., 2009). I r, resulting gues for thr ples 301, 3 ermost lay most unit ( cal composi tephra was re is no cle ples from centrations of proximal al alterati ved in diffe eceiving env entologica hen depo an reach 10 n result eit m remobil n the case o in the cre ee glasses c 07 and 2017 er (Figure Figure 4-6) tion of the erupted at t ar distinctio Gasparotto . YTT deposits on rent types o ironment ( l processes sited in ter m or more her from er isation of l f marine de ation of a g ollected from , Beddoe-S 4-6), plots a , plots at th YTT glass in he source. A n between et al. (2000 in Sumatra (B f marine an i.e. deep m involved in restrial envi in thicknes osion of no ocal fallout position, tu radual uni a pyroclas tephens et a t the lower e uppermo distal depo s expected marine and ) are not sh eddoe-Steph d continent arine or car the reworki ronments, s (Figure 1- n-welded p deposits fr rbidites an t of volcani tic unit in S l., 1983). Sa left in Figu st right in F sits varies a for a diagra continenta own becaus ens et al., 198 al settings. T bonate plat ng (turbidit the ash can 11, Figure 5 yroclastic f om surroun d bioturbati c material umatra (Fi mple 301, f re 4-5. Sam igure 4-5. ccording to m showing l ash. Note e these aut 3). he ash feat form; lacust es, floods, w accumulat -3, Figure 6 low deposit ding hillslo on can disp mixed with gure rom ple This the only that hors ures rine ind e in -3). s in pes erse the auto depo bact oxid indi Figu func reco Exce sam Na2O simi mar resp Figu FeO/ mag SiO2 redu chthonous sited, are eria and ve es are sensi cator of the re 4-7 show tion of the vered from ptions are t ples; and C over K2O lar to that o ine samples ect to the re re 4-7 Comp Al2O3. The a matic source. /Al2O3. For th ce the effect o sediments exposed to getations (F tive to temp influence o s the Na2O FeO/Al2O marine bas he Sumatra entral India . Samples fr f the sampl . Indian sam st of the con arison of di bscissa is the In this diag e abscissa w f inter-labora (Thompson the action anning and erature and f the receivin /K2O ratio 3 (Fig. 4-7a ins plot to t samples, wh n Ocean B om the Sout es from con ples from W tinental sam stal ash elem ratio of two ram, alteratio e did not plo tory bias (Fig et al., 19 of water Schink, 19 water chem g environm (an indicato ) and SiO2 he left of th ich show ~ asin (CIOB h China Sea tinental site estgate et ples (Fig. 4 ental ratios, immobile elem n causes a v t the silica co ure 4-4). 86). This i (meteoric o 69). Mobile istry (Pere ent on the r of diagen /Al2O3 (Fig e diagram, 20% lower ) samples. (SCS) and s (Fig. 4-7b al. (1998) h -7b). grouped acc ents, which ertical shift o ncentration, mplies that r marine), elements s z, 2009). Th chemistry o esis and of . 4-7b) rat distinct fro Na2O/K2O t The latter a the Arabian ), and diffe ave a ~ 4% ording to loc records the o f data points but rather its the ash g sediments, uch as alka ey are there f the glasses aqueous le ios. Most a m the conti han the rest re notably Sea have si r from that higher SiO2 ation. (a) N riginal comp . (b) Na2O/K ratio to alum 61 rains, once organisms li and silica fore a good . aching) as a sh samples nental sites of the YTT enriched in lica content of the other /Al2O3 with a2O/Ka2O vs osition of the a2O ratio vs ina, so as to , . . . 62 4.5 Discussion 4.5.1 Analytical bias Analyses of the same glass samples performed in several laboratories show minimal offsets of 0.5- 1% that are due to inter-laboratory shifts, possibly owing to different techniques applied, instrumentation, chemical and rock standards used. For example, the geochemistry of the sample from JWP site 3 (India) analysed in this work is similar to the data presented by Petraglia et al. (2007), collected from the same stratigraphic section. However, both are ca. 0.3% lower in Al2O3 than the sample characterised by Smith et al. (2011), analysed in another laboratory. The analyses from this research and from Petraglia et al. (2007) were conducted in the same laboratory with the same instrument. Similarly, there is a 1% difference in the SiO2/Al2O3 ratio of the Indian samples from Westgate et al. (1998) as compared with the same Indian samples reported by (Shane et al., 1995). This could also account for the post-depositional shift in SiO2/Al2O3 ratios shown by the samples from Westgate et al. (1998) in Fig. 4-7b. Such discrepancies are probably related to analytical bias and/or to large sample heterogeneity. These results suggest that geochemical analyses of the YTT in this database are affected by a systematic inter-laboratory uncertainty of ca. ± 1%. These variations do not mask the broad characterisation of the YTT, nor the magmatic differentiation shown in Figure 4-5. This is because the inter-laboratory error is smaller than the variations related to the magma chemistry. However, they do suggest that any study endeavouring to reveal very subtle geochemical variability should be based on analyses from a single laboratory, performed in a short period under stable instrumental conditions (Kuehn et al., 2011). 4.5.2 Pre-eruptive magmatic differentiation Since immobile elements reflect the initial magma composition, the origin of the wide and tightly correlated variation between FeO/TiO2 and Al2O3/TiO2 shown in Figure 4-5 is likely to be a primary magmatic process. The trend in FeO/TiO2 may reflect a progressive tapping of deeper, less evolved magma during the eruption. However, the increase in Al is more difficult to explain in such a scenario. The simplest way to produce the observed correlation is fractional crystallisation. Low Ti reflects crystallization of Fe-Ti oxides: the process depletes the melt in Ti and show It is pha pha mag 4.5. The are elem pres erup proc F a r O 2 Fe to form s the stron also noted ses of the er ses (Figure 4 matic cham 2.1 YTT ve large YTT d rarer. Due ents of sam ented (Figu tions are s esses. igure 4-8 Im s crosses, wh esemble the TT and YTT 001 (SCS), P Ti-rich mi g control of that low va uption, wh -5). The ch ber that ari rsus OTT atabase allo to the deba ples attrib re 4-8). A imilar in t mobile eleme ile the eight YTT glasses. . OTT sampl attan et al. (20 nerals, such fractional c lues of FeO ile high FeO anges in Fe ses through ws compar te on the uted beyon ll the samp erms of bo nt ratios for Y undoubted O The graph cl es from: Deh 10) (CIOB), S as ilmenite rystallizatio /TiO2 broad /TiO2 value O/TiO2 thu fractional c ison of a sub age of the M d doubt to les overlap th chambe TT versus O TT samples early shows t n et al. (1991) mith et al. (2 , biotite or n on the YT ly correspo s are found s also reflec rystallisation stantial nu orgaon as the OTT . The patte r dynamic TT. The YTT are shown a hat major ele (90° E Ridge 011) (90° E ri hastingsite. T glass geoc nd to ash ej in the ash t the compo . mber of YT h, a compa (~ 800 ka) rn suggests s and pre-e samples from s filled symb ments canno ), Lee et al. (2 dge). The diagra hemistry. ected durin ejected duri sitional zon T samples. O rison of th and YTT ( that the T ruptive dif figure 4-5 a ols. The OTT t discriminate 004) (SCS), L 63 m therefore g the initial ng the final ation of the TT studies e immobile ~ 73 ka) is oba super- ferentiation re shown samples between iang et al. 64 The K concentrations of Morgaon ash reported by Westaway et al. (2011) are compatible with the typical K2O concentrations of the YTT; therefore, the possibility of an older K-Ar age due to a massive (>90 %), very recent K depletion is excluded. The ratios of the Morgaon ash are higher in FeO/TiO2 than the average YTT ash found in India. They are similar to YTT glass samples from Sumatra (Chesner, 1998), but also to the OTT sample 17957 from the South China Sea (Lee et al., 2004, Figure 4-8). Taking into account that the immobile major elements cannot distinguish between OTT and YTT, the hypothesis that Morgaon ash is sourced from the OTT eruption cannot be excluded by the present data. 4.5.3 Post-depositional alteration and definition of geochemical provinces To investigate secondary element mobilisation, the mobile elements (alkalis) sensitive to secondary alteration were compared. The SiO2/Al2O3 ratio takes into account the secondary mobilisation of Si by leaching, while minimising the influence of primary Si variation (e.g. due to magma reservoir zonation, § 4.5.2). However, as Al is also enriched in the residual magma, the SiO2/Al2O3 ratio is much more sensitive to secondary leaching than to primary magmatic processes. Samples from the Arabian Sea and Bay of Bengal presented in Schulz et al. (1998) and sample MD97-2151 from the South China Sea (Song et al., 2000; see Table 4-3) present distinctive lower alkali ratios coupled with high Si. This places the samples in the lowermost part of the graph (Fig. 4-7b). However, the raw data (Table 4-3) show that the low alkali ratio is due to a significant low amount of Na (1.69 wt%), combined with unusually high Si content (79 wt%). It is possible that the analyses performed by these authors resulted in Na loss and migration of the latter into Si. The phenomenon is common when analysing tephra with EPMA and it can be avoided using few simple procedures (Kuehn et al., 2011). On the other hand, the samples from Sumatra have Na/K ratios ~ 20% lower than those of the rest of the analysed samples (Fig. 4-7). The samples from Sumatra are not tephra, but welded tuff and pumices. The exposure of the welded rocks to tropical weathering, coupled with differences between welded rock and tephra, can explain the differences between the Sumatra samples and the rest of the database. 65 It is difficult to speculate on the observed post-depositional weathering trends and relate them unmistakeably to specific environments of deposition (i.e. deep marine ocean, continental etc.), since several samples (i.e. the Nineties Ridge tephra) follow none of these categories. However, broadly, the Bay of Bengal tephra show 7–8% lower Na/K ratio and ~ 3% lower SiO2/Al2O3 ratio with respect to those from continental sites; the CIOB presents SiO2/Al2O3 loss (~ 3%); the SCS and the Arabian Sea data show a lower Na/K ratio (~ 7%) compared to the continental sites, but have SiO2/Al2O3 ratios similar to ash deposited in subaerial environments. Site-specific pore water chemistry could account for the evidenced desilication and alkali loss. Data from the Ocean Drilling Project show that the silica content of the interstitial water of the ODP1143 core (2771 water depth, see Table 4-2), in the South China Sea is between 100 to 900 times higher than the silica in the ODP 116-718 core, from the Central Indian Ocean (4730 m water depth). Alkalinity is also higher in the South China Sea (10.1 mM versus 5.13 mM of the Indian Ocean), while salinity appears similar for both the interstitial water. The ODP website reports only one drilled core in the Bay of Bengal, the DSDP 22-218, in the lower part of the fan. Data regarding specific elements are not available; however the reported salinity of the Bay of Bengal interstitial water is averagely 2% lower than the South China and Indian Ocean water. Furthermore, differences in individual ion concentrations (e.g. Si, Na+, K+) could account for the differences showed in Fig. 7-8. For example, alkali migration is a common feature in ash buried in marine environments (Shikazono et al., 2005), and several marines sites (i.e. Bay of Bengal, South China Sea, Arabian Sea) show a 7–8% lower Na/K ratio. However, the sites from the Central Indian Ocean have higher level of alkali, similar to continental sites. The CIOB ash might have been naturally enriched in alkali. Another possibility is that the CIOB ash was lower in alkali concentration and this might have inhibited the hydrogen exchange necessary to induce significant alkali migration (Cerling et al., 1985). From the discussion above, it appears that secondary alteration can influence the alkali and silica concentrations in the rhyolitic glass. Marine deposits from the Bay of Bengal overall show ~ 8% lower Na/K and ~ 3–4% lower SiO2/Al2O3 ratios than continental sites. The South China Sea tephra show a similar alkali loss, but have SiO2/Al2O3 ratios similar to the continental sites. The 66 Central Indian Ocean ash show silica loss of ~3-4% with respect to the continental samples, but does not show alkali loss similar to the other marine sites. 4.6 Conclusion The samples analysed at several laboratories reveal a baseline inter-laboratory variability of ± 1 %. Although these variations do not influence the characterisation of the YTT fingerprints, these internal differences should be taken into account when using chemical fingerprints for analytical studies that require a resolution higher than 1 %. Major differences are found when comparing immobile elements ratios (FeO/TiO2 and Al2O3/TiO2). Glass varies from higher-TiO2 rhyolite (FeO/TiO2 ratio between 0.1 and 10), to lower-TiO2 rhyolite (FeO/TiO2 >22). The ratios indicate the stages of magma fractional crystallisation. Crudely, the enrichment in FeO/TiO2 also reflects the magma drawdown depth vs. time of the eruption: the first phase of the eruption ejected the most evolved magma, situated in the upper part of the chamber. This is consistent with fractional crystallization driving the process of zonation of the YTT magma reservoir. The mobile (Na, K and Si) versus immobile (Fe and Al) element plots showed as differences relate to site-specific water pore chemistry, namely Si-enrichment, and individual ion concentrations can influence the content of alkali and silica of the marine tephra, with variations that range from 7-8% for alkali and 3-4 % for silica. Geochemical fingerprinting is an important tool which allows the YTT distal deposits to be used as chronological markers. Once the ash has been identified, the tephra deposits need to be analysed in their stratigraphic context, to establish their value as a stratigraphic marker. Sedimentological and stratigraphic features of the tephra deposits thus need to be carefully interpreted in order to understand the path and mechanisms that lead to the deposition and preservation of the ash. The following chapters (five and six) deal with the assessment and understanding of such mechanisms, using YTT tephra layers in two distinct environmental settings. 67 Table 4-2 Literature data used for geochemical comparison. Locations listed here are reported in Figure 4-1; w.d. = water depth. In case of multiple sampling from the same core (i.e. Gasparotto et al., 2000) the lowest sample was used. FeOtot values from Chesner (1998) and Pattan et al. (2001) calculated from Fe2O3. Sample Location Environment Reference MD01-2393 South China Sea Submarine/continental slope (1230 m w.d.) Liu et al., (2006) MD97-2151 South China Sea/ south-eastern Vietnam Submarine/shallow shelf (Wan–An Shallow, 1550 m w.d.) Song et al. (2000); Chen et al. (2000) 17961–2 South China Sea Submarine/ carbonate platform with hemipelagic sediment drape (1968 m w.d.) Bühring et al. (2000) 17962–4 South China Sea Submarine/ carbonate platform with hemipelagic sediment drape (1969 m w.d.) Bühring et al. (2000) ODP1143 (layer A) South China Sea Submarine/unspecified (2782 m w.d.) Liang et al. (2001) ODP758 (layer A) Southern Bay of Bengal/90east Ridge Submarine/deep water/ on an echelon block 1000 m above the Bengal fan (2924 m w.d.) Dehn et al. (1991) SO130-289KL Northern Arabian Sea/Pakistan margin Submarine/continental slope off the Indus delta/oxygen minimum zone (571 m w.d.) Schulz et al. (2002),Von Rad et al. (2002) UT1069 Indian subcontinent/Narmada valley Subaerial/fluvial/ semi-arid Shane et al. (1995) Kota Tampan Malaysia Subaerial/palaeofluvial/tropic al humid Ninkovich et al. (1978a) ID 680 Toba, Siguragura (glass fraction) Subaerial/volcanic caldera/tropical humid Ninkovich et al. (1978a, 1979) RC14-37 Southern Bay of Bengal/90east Ridge Submarine/deep sea Ninkovich et al. (1978a, 1979) 94A5-G Toba (glass fraction from pumice) Subaerial/volcanic caldera/tropical humid Chesner (1998) 68 63A1-G Toba (glass fraction from pumice) Subaerial/volcanic caldera/tropical humid Chesner (1998) R301(M) Toba, Haranggaol (glass matrix from welded tuff) Subaerial/volcanic caldera/tropical humid Beddoe- Stephens et al. (1983) R303(M) Toba, Haranggaol (glass matrix from unwelded tuff) Subaerial/volcanic caldera/tropical humid Beddoe- Stephens et al. (1983) 2017(M)-1 Toba (glass matrix from unwelded pumice) Subaerial/volcanic caldera/tropical humid Beddoe- Stephens et al. (1983) 2017(M)-2 Toba (glass matrix from unwelded pumice) Subaerial/volcanic caldera/tropical humid Beddoe- Stephens et al. (1983) SO90-94KL Northern Arabian sea/ Indus fan Submarine/ unspecified (2109 m w.d.) Schulz et al. (2002) SO93-115KL Middle Bengal Fan Submarine/unspecified Schulz et al. (2002) UT1068 Kukdi River W.India Subaerial/fluvial/semi-arid Shane et al. (1995) UT788 Serdang, Malaysia Subaerial/lacustrine/tropical humid Shane et al. (1995) CR-02 Central Indian Basin Submarine/deep ocean/ abyssal siliceous oozes (4900 m w.d.) Pattan et al. (1999) CR-05 Central Indian Basin Submarine/deep ocean/ abyssal siliceous oozes (4300 m w.d.) Pattan et al. (1999) NR-1 Central Indian Basin Submarine/deep ocean/ abyssal siliceous oozes (5250 m w.d.) Pattan et al. (1999) NR-21 Central Indian Basin Submarine/deep ocean/ abyssal siliceous oozes (5325 w.d.) Pattan et al. (1999) NR-35 Central Indian Basin Submarine/deep ocean/ abyssal siliceous oozes (5450 m w.d.) Pattan et al. (1999) NR-54 Central Indian Basin Submarine/deep ocean/ abyssal siliceous oozes (5200 m w.d.) Pattan et al. (1999) 69 SK-226 Central Indian Basin Submarine/deep ocean/ abyssal siliceous oozes (5270 m w.d.) Pattan et al. (1999) SS-657 Central Indian Basin Submarine/deep ocean/ abyssal siliceous oozes (5050 m w.d.) Pattan et al. (1999) WCM-1 Western Continental Margin of India/Arabian Ocean Submarine/ (2300 m w.d) Pattan et al. (2001) WCM-2 Western Continental Margin of India/Arabian Ocean Submarine/ (2300 m w.d) Pattan et al. (2001) 1KL 395 Bay of Bengal Submarine/continental slope/ hemipelagic (395 cm from the top of the piston core.) Gasparotto et al. (2000) 22KL 104 Bay of Bengal Submarine/foot of seamount in fan area/pelagic (104 cm from the top of the piston core.) Gasparotto et al. (2000) 22KL 719.5 Bay of Bengal Submarine/foot of seamount in fan area/pelagic (718 cm from the top of the piston core.) Gasparotto et al. (2000) 28KL 227 Bay of Bengal Submarine/floor of seamount in fan area/pelagic (227 cm from the top of the piston core) Gasparotto et al. (2000) 29KL 170 Bay of Bengal Submarine/turbidite plain/hemipelagic (170 cm from the top of the piston core) Gasparotto et al. (2000) 29KL 173 Bay of Bengal Submarine/ turbidite plain/hemipelagic (169 cm from the top of the piston core Gasparotto et al. (2000) 29KL 176 Bay of Bengal Submarine/ turbidite plain/hemipelagic (169 cm from the top of the piston core.) Gasparotto et al. (2000) 42KL Bay of Bengal Submarine/mud waves above plain level/hemipelagic (267 cm from the top of the piston core Gasparotto et al. (2000) 70 45KL Bay of Bengal Submarine/channel levee/turbidite (1067 cm from the top of the piston core.) Gasparotto et al. (2000) 45KL 1075–1078 Bay of Bengal Submarine/ channel levee/turbidite (1075 cm from the top of the piston core.) Gasparotto et al. (2000) 47KL 151.5–154 Bay of Bengal Submarine/trapped levee in old channel/hemipelagic with turbidite (152 cm from the top of the piston core) Gasparotto et al. (2000) 47KL 161–162 Bay of Bengal Submarine/ trapped levee in old channel/ hemipelagic with turbidite (161 cm from the top of the piston core) Gasparotto et al. (2000) 51KL 721–723 Bay of Bengal Submarine/marginal levee of active channel/turbidite (721cm from the top of the piston core) Gasparotto et al. (2000) 51KL 729–732 Bay of Bengal Submarine/marginal levee of active channel/turbidite (729 cm from the top of the piston core) Gasparotto et al. (2000) 51KL 738–741 Bay of Bengal Submarine/marginal levee of active channel /turbidite (738cm from the top of the piston core) Gasparotto et al. (2000) 115KL 391–393 Bay of Bengal Submarine/middle fan, distant to channel/ hemipelagic (398 cm from the top of the piston core) Gasparotto et al. (2000) 115KL 397–399 Bay of Bengal Submarine/middle fan, distant to channel/ hemipelagic (389 cm from the top of the piston core) Gasparotto et al. (2000) 124KL 454–456 Bay of Bengal Submarine/upper fan/ hemipelagic (454 cm from the top of the piston core) Gasparotto et al. (2000) NP4, NP6, NP7 & NP8 Sumatra Subaerial/ volcanic caldera/ tropical humid Smith et al. (2011) NP5 Lenggong, Malaysia Subaerial/fluvial/tropical humid Smith et al. (2011) 71 JWP138 Jwalapuram, India Subaerial/ palaeolacustrine/arid Smith et al. (2011) G05309 & GOC1 Son Valley, India Subaerial/fluvial/semi-arid Smith et al. (2011) JWP3-18s Jwalapuram, India Subaerial/ palaeolacustrine/arid Petraglia et al. (2007) UT1069 Indian subcontinent Subaerial/fluvial/ semi-arid Westgate et al. (1998) UT1070 Indian subcontinent Subaerial/fluvial/semi-arid Westgate et al. (1998) UT1299 Indian subcontinent Subaerial/fluvial/ semi-arid Westgate et al. (1998) UT1359 Indian subcontinent Subaerial/fluvial/ semi-arid Westgate et al. (1998) UT1358 Indian subcontinent Subaerial/fluvial/ semi-arid Westgate et al. (1998) UT1300 Indian subcontinent Subaerial/fluvial/ semi-arid Westgate et al. (1998) UT1361 Indian subcontinent Subaerial/fluvial/ semi-arid Westgate et al. (1998) UT1362 Indian subcontinent Subaerial/fluvial/ semi-arid Westgate et al. (1998) UT1071 Indian subcontinent Subaerial/fluvial/ semi-arid Westgate et al. (1998) UT1072 Indian subcontinent Subaerial/fluvial/ semi-arid Westgate et al. (1998) UT1134 Indian subcontinent Subaerial/fluvial/ semi-arid Westgate et al. (1998) UT1135 Indian subcontinent Subaerial/fluvial/ semi-arid Westgate et al. (1998) UT1068 Indian subcontinent Subaerial/fluvial/ semi-arid Westgate et al. (1998) Bukit Sapi Lenggong, Malaysia Subaerial/fluvial/tropical humid This thesis Kampung Luat 2 Lenggong, Malaysia Subaerial/fluvial/tropical humid This thesis Kampung Luat 3 Lenggong, Malaysia Subaerial/fluvial/tropical humid This thesis Bori Western India Subaerial/fluvial/semi-arid This thesis JWP-3 Southern India Subaerial/ palaeolacustrine/arid This thesis Morgaon Western India Subaerial/fluvial/semi-arid This thesis 72 Table 4-3. Major element compositions (on volatile-free basis) of glass shards from selected literature data. Values represent average; all data were recalculated to 100% for comparative purposes. FeO*, all Fe as FeO. Available original totals are reported in red. Sample Location Reference SiO2 Al2O3 TiO2 FeO* MnO MgO CaO Na2O K2O SO130-289KL Arabian Sea Schulz et al. (2002) 77.74 12.65 0.06 0.91 0.07 0.06 0.72 2.74 5.05 SO90-94KL Arabian Sea Schulz et al. (2002) 79.27 12.56 0.05 0.92 0.08 0.05 0.74 1.69 4.62 SO130-289KL Arabian Sea von Rad (2002) 77.74 12.65 0.05 0.91 0.07 0.06 0.72 2.75 5.04 SO130-289KL Arabian Sea von Rad (2002) 74.46 12.12 0.05 0.87 0.07 0.06 0.69 2.63 4.83 WCMI Arabian Sea/ Western Continental Margin Pattan et al., (2001) 76.94 12.53 0.12 0.88 0.12 - 0.83 3.40 5.04 1KL 395 Bay of Bengal Gasparotto et al. (2000) 76.89 12.81 - 0.83 - 0.1 0.79 3.26 5.32 28KL 227 Bay of Bengal Gasparotto et al. (2000) 76.99 12.86 - 0.88 - 0.12 0.82 2.96 5.36 29KL 176 Bay of Bengal Gasparotto et al. (2000) 76.9 12.79 - 0.88 - 0.1 0.81 3.17 5.35 42KL Bay of Bengal Gasparotto et al. (2000) 76.89 12.98 - 0.85 - 0.07 0.82 3.05 5.35 45KL 1075–1078 Bay of Bengal Gasparotto et al. (2000) 76.94 12.94 - 0.84 - 0.11 0.78 3.23 5.17 47KL 161–162 Bay of Bengal Gasparotto et al. (2000) 76.91 12.89 - 0.87 - 0.1 0.78 3.23 5.22 51KL 738–741 Bay of Bengal Gasparotto et al. (2000) 77.06 12.86 - 0.85 - 0.09 0.77 3.13 5.23 115KL 397–399 Bay of Bengal Gasparotto et al. (2000) 77.2 12.85 - 0.85 - 0.07 0.72 3.2 5.11 124KL 454–456 Bay of Bengal Gasparotto et al. (2000) 77.01 12.8 - 0.9 - 0.11 0.75 3.21 5.23 22KL 719.5 Bay of Bengal Gasparotto et al. (2000) 77 12.81 - 0.87 - 0.07 0.77 3.13 5.36 SO93-115KL Bengal Fan (Middle) Schulz et al. (2002) 78.6 12.59 0.06 1.03 0.06 0.06 0.76 1.8 5.03 CR-02 Central Indian Basin Pattan et al., (1999) 76.53 12.83 0.07 0.96 0.08 0.04 0.82 3.27 5.25 CR-05 Central Indian Basin Pattan et al., (1999) 76.73 12.79 0.08 0.88 0.06 0.04 0.76 3.34 5.14 NR-1 Central Indian Basin Pattan et al., (1999) 76.9 12.74 0.09 0.93 0.07 0.05 0.79 3.41 5.09 73 Sample Location Reference SiO2 Al2O3 TiO2 FeO* MnO MgO CaO Na2O K2O NR-21 Central Indian Basin Pattan et al., (1999) 76.94 12.82 0.06 0.89 0.06 0.05 0.78 3.42 5 NR-35 Central Indian Basin Pattan et al., (1999) 76.95 12.69 0.07 0.91 0.05 0.05 0.76 3.44 5.09 NR-54 Central Indian Basin Pattan et al., (1999) 76.94 12.74 0.06 0.95 0.08 0.04 0.78 3.46 4.98 SK-226 Central Indian Basin Pattan et al., (1999) 76.81 12.76 0.05 0.92 0.05 0.05 0.8 3.48 5.07 SS-657 Central Indian Basin Pattan et al., (1999) 76.89 12.75 0.07 0.91 0.05 0.06 0.79 3.46 5.04 JWP3-18s India (Jwalapuram) Petraglia et al. (2007) 77.48 12.26 0.06 0.87 0.08 0.06 0.80 3.44 4.96 JWP3-18s India (Jwalapuram) Petraglia et al. (2007) 73.59 11.65 0.05 0.831 0.08 0.05 0.76 3.27 4.71 UT1068 India Shane et al. (1995) 77 12.6 0.05 0.89 0.07 0.06 0.76 3.35 5.04 UT1069 India Shane et al. (1995) 77.15 12.67 0.06 0.86 0.08 0.06 0.78 3.26 5.08 UT1134 India Shane et al. (1995) 77.5 12.58 0.07 0.89 0.07 0.06 0.79 3.29 5.03 UT1135 India Shane et al. (1995) 76.99 12.63 0.06 0.9 0.07 0.06 0.77 3.22 5.15 UT1136 India Shane et al. (1995) 77.26 12.59 0.05 0.92 0.06 0.05 0.74 3.22 4.95 UT1137 India Shane et al. (1995) 77.12 12.63 0.05 0.94 0.06 0.05 0.80 3.14 5.06 UT1138 India Shane et al. (1995) 77.22 12.53 0.05 0.94 0.06 0.05 0.73 3.18 5.06 JWP138 India Smith et al. (2011) 77.36 12.46 0.05 0.87 0.07 0.06 0.75 3.25 4.96 G05309 & GOC1 India Smith et al. (2011) 76.92 12.57 0.06 0.87 0.07 0.05 0.78 3.36 5.16 UT1069 India Westgate et al. (1998) 77.78 12.26 0.05 0.86 0.05 0.04 0.8 3.08 4.94 UT1070 India Westgate et al. (1998) 77.63 12.21 0.05 0.87 0.06 0.06 0.8 3.13 5.05 UT1299 India Westgate et al. (1998) 77.81 12.02 0.05 0.86 0.03 0.05 0.75 3.24 5.03 UT1359 India Westgate et al. (1998) 77.76 12.06 0.06 0.88 0.06 0.05 0.76 3.21 5.02 UT1358 India Westgate et al. (1998) 77.76 12.1 0.03 0.87 0.06 0.05 0.8 3.08 5.12 74 Sample Location Reference SiO2 Al2O3 TiO2 FeO* MnO MgO CaO Na2O K2O UT1300 India Westgate et al. (1998) 77.68 12.12 0.05 0.88 0.05 0.06 0.83 3.22 4.96 UT1361 India Westgate et al. (1998) 77.69 12.09 0.09 0.88 0.05 0.06 0.82 3.14 5.04 UT1362 India Westgate et al. (1998) 77.67 12.14 0.07 0.89 0.06 0.05 0.75 3.24 4.98 UT1071 India Westgate et al. (1998) 77.64 12.14 0.05 0.87 0.05 0.04 0.77 3.22 5.09 UT1072 India Westgate et al. (1998) 77.57 12.16 0.05 0.92 0.07 0.05 0.83 3.17 5.06 UT1134 India Westgate et al. (1998) 77.58 12.12 0.07 0.9 0.06 0.06 0.78 3.1 5.18 UT1135 India Westgate et al. (1998) 77.71 12.04 0.08 0.85 0.07 0.05 0.74 3.14 5.17 UT1068 India Westgate et al. (1998) 77.62 12.2 0.07 0.9 0.07 0.05 0.79 3.17 5 Kampung Luat 2 Malaysia (Lenggong) Gatti et al. (2012) 77.39 12.27 0.04 0.90 0.08 0.07 0.78 3.27 5.22 Kampung Luat 2 Malaysia (Lenggong) Gatti et al. (2012) 74.62 11.83 0.04 0.87 0.08 0.07 0.75 3.15 5.03 UM6315 Malaysia (Kota Tampan), glass shard fraction Ninkovich et al. (1978a) 76.09 14.25 0.17 0.841 0.05 0.10 1.05 2.62 4.82 UM6315 Malaysia (Kota Tampan), glass shard fraction Ninkovich et al. (1978a) 72.6 13.6 0.16 0. 75 2 0. 05 3 0.05 0.1 1.00 2.50 4.60 UT778 Malaysia (Serdang) Shane et al. (1995) 77.21 12.54 0.05 0.89 0.08 0.06 0.72 3.4 4.88 NP5 Malaysia (Lenggong) Smith et al., (2011) 77.24 12.59 0.06 0.87 0.07 0.06 0.77 3.09 5.13 ODP758 Nineties ridge Dehn et al. (1991). 77.54 12.53 0.08 0.83 - 0.05 0.80 3.02 5.15 UT1363-ODP758 Nineties ridge Westgate et al. (1998) 77.68 12.27 0.08 0.84 0.08 0.05 0.79 3.16 4.88 RC14-37 Nineties ridge Ninkovich et al. (1978a) 74.17 13.53 0.14 1.031 0.07 0.26 1.70 3.82 5.27 RC14-37 Nineties ridge Ninkovich et al. (1978a) 71.80 13.10 0.14 0. 15 2 0. 85 3 0.07 0.25 1.65 3.70 5.10 17961–2 South China Sea Bühring et al. (2000) 78.04 12.45 0.05 0.85 0.07 0.06 0.76 2.86 4.86 17962–4 South China Sea Bühring et al. (2000) 78.05 12.52 0.05 0.84 0.07 0.06 0.77 2.78 4.86 75 Sample Location Reference SiO2 Al2O3 TiO2 FeO* MnO MgO CaO Na2O K2O ODP1143 South China Sea Liang et al. (2001) 77.93 12.82 0.05 0.87 0.1 0.02 0.76 2.66 4.79 MD01-2393 South China Sea Liu et al. (2006) 76.78 13.09 0.23 0.97 0.25 0.87 0.8 2.75 4.26 MD97-2151 South China Sea Song et al. (2000) 79.38 12.78 0.07 0.89 0.06 0.04 0.75 1.47 4.56 R301 Toba (matrix glass) Beddoe-Stephens et al. (1983) 77.36 12.66 0.10 0.92 0.07 0.02 0.66 3.31 4.90 R301 Toba (matrix glass) Beddoe-Stephens et al. (1983) 74.32 12.16 0.10 0.88 0.07 0.02 0.63 3.18 4.71 R303 Toba (matrix glass) Beddoe-Stephens et al. (1983) 77.88 12.55 0.03 0.66 0.06 0.01 0.79 2.76 5.26 R303 Toba (matrix glass) Beddoe-Stephens et al. (1983) 74.32 11.98 0.03 0.63 0.06 0.01 0.75 2.63 5.02 2017_a Toba (matrix glass) Beddoe-Stephens et al. (1983) 77.49 12.84 0.04 0.88 0.05 0.07 0.63 2.64 5.35 2017_a Toba (matrix glass) Beddoe-Stephens et al. (1983) 74.72 12.38 0.04 0.85 0.05 0.07 0.61 2.55 5.16 2017_b Toba (matrix glass) Beddoe-Stephens et al. (1983) 77.57 12.77 0.03 0.93 0.04 0.05 0.52 2.62 5.46 2017_b Toba (matrix glass) Beddoe-Stephens et al. (1983) 74.89 12.33 0.03 0.9 0.04 0.05 0.5 2.53 5.27 63A1-G Toba (glass from pumice) Chesner (1998) 76.83 12.93 0.08 1.09 0.07 0.18 0.94 2.94 4.82 94A5-G Toba (glass from pumice) Chesner (1998) 78.12 12.04 0.04 0.84 0.06 0.15 0.62 2.79 5.26 6A2-G Toba (glass from pumice) Chesner, (1998) 77.6 12.78 0.08 0.75 0.06 0.20 0.80 2.6 5.03 Id 680 Toba (Si Gura Gura), glass shard fraction Ninkovich et al. (1978a) 74.65 13.34 0.11 0.961 0.06 0.36 2.27 2.89 5.27 Id 680 Toba (Si Gura Gura), glass shard fraction Ninkovich et al. (1978a) 72.20 12.90 0.11 0. 30 2 0. 70 3 0.06 0.35 2.20 2.80 5.10 NP4, NP6, NP7 & NP8 Toba Smith et al., (2011) 77.24 12.54 0.06 0.85 0.07 0.05 0.78 3.1 5.2 1 Values from Ninkovich et al. (1978a and 1979) were reported as Fe2O3 and FeO. It is inappropriate to simply add or subtract FeO mass % and Fe2O3 mass % to obtain the FeOtot. In order to calculate the FeOtot I applied the formula ∑ FeO= FeO+(Fe2O3 ÷ 1.11).2 Fe2O3; 3 FeO. 77 Chapter 5. Stratigraphic significance of the YTT layer in the Son valley Based on Gatti et al. (2011) Abstract The Middle Son Valley was the first site on the Indian subcontinent of reported discovery of YTT deposits. Although distal ash has been studied since the 1980s, its stratigraphy and the mechanisms involved in its transport and deposition have not been previously assessed. This chapter reports on the stratigraphy of the YTT ash layers in alluvial deposits of the Middle Son Valley, in order to reconstruct the taphonomy of the tephra deposits and the dynamics of their deposition. The YTT occurrences in the Middle Son Valley are shown to be unreliable as chronostratigraphic markers for millennial scale palaeoenvironmental reconstruction. 5.1 Introduction The Middle Son Valley (Madhya Pradesh, North Central India) is the first locality in India from which findings of YTT were reported (Williams and Royce, 1982). Initially these sites were investigated for the abundance of Middle Palaeolithic archaeological assemblages (Acharyya and Basu, 1993). However, since the 1980s they have become the focus of palaeoenvironmental studies for understanding the immediate and longer-term impacts of the YTT super-eruption on climate and humans (Basu et al., 1987; Bobe et al., 2002). To improve understanding of the extent and severity of the environmental impacts of the YTT eruption, it is critical to determine how long it took for the ash to be re-deposited and consolidated on the landscape. The longer the ash remained mobile in the environment, the more severe the impact on vegetation and associated ecosystems would have been (Fritz, 1980; Collins and Dunne, 1986). Tephra successions, if suitably preserved, can be used as chronostratigraphic markers. The YTT stratum in the Middle Son Valley, in particular, has been repeatedly used as a marker horizon in archaeological investigations (Williams and Royce, 1982; Jones and Pal, 2005). For example, using artefacts in secondary contexts, Jones and Pal (2009) observed a change in lithic technology 78 between the tools below and above the ash, and proposed a shift in hominid behaviour during the Upper Pleistocene. This suggested that the Toba eruption contributed to such changes. Furthermore, recent studies by Jones (2010) and Jones (2012) used the YTT layer at two localities in the Son Valley, Ghoghara and Khunteli, to investigate the link between Toba ash, environmental disruption and hominid evolution. They proposed that the depositional regime in the Middle Son valley changed following the ash-fall, and this could have affected hominid population dynamics in the area. Despite the frequent use of the Son Valley YTT stratum for archaeological and geological studies, its reliability as a stratigraphic marker has been given limited consideration. The aim of this chapter is to contextualise the distal YTT stratum of the Middle Son Valley through a study of the stratigraphy of the volcaniclastic sequences, in order to provide textural and structural details of the tephra units. This chapter presents a series of stratigraphic sections containing YTT tephra located between the Rehi River and the site of Khunteli (Figure 5-1), exposed in the modern riverside cliffs. The characteristics of the preserved ash lead to an interpretation of the river activity before and after the eruption. This, together with the field evidence of their sedimentary context, suggests that the YTT deposits of the Son Valley area might not provide a reliable chronostratigraphic marker in the region for long-term palaeoenvironmental reconstructions and archaeological correlations. An exception is the site of Ghoghara. F l a 5.2 The nort char win Sept runo The tribu maj Mad and Hol enco chan dom Son igure 5-1 Lo ogged sites p nd NASA). Study Are Middle So h central In acterised b ters (Octobe ember, the ff, which h Son (784 k taries feedi or E-W tec hya Prades shale bedr ocene alluv unter Midd nel has inc inated by s river has b cation of the resented in th a n Valley lie dia (24° 7 y hot hum r-March) w topography as deeply in m long) is ng into the tonic lineam h, the Son f ock of the ial plains le Proteroz ised the m and (Bhatta een strongly tephra sites is work. DEM s 100 km so ’ N, 80°/83° id summer ith low pre and geomo cised the riv one of the River Gang ent, the N lows north- Vindhyan (Banerjee oic sandsto etamorphic charyya and influenced in the Son V from ASTE uth of Alla 50’ E, Figu s (April-Se cipitation. A rphology of er terraces. longest riv es. It flows, armada fau northwest a Super-Grou and Jeevan ne of the Ka bedrock to Morad, 19 by climatic alley. The ye R GDEM (A habad and re 5-1). Th ptember, te ffected by t the hills an ers of Indi as does the lt (Williams nd cuts thr p (Singh, 1 kumar, 200 imur Rang a depth of 93). Throug factors (ref llow dots on STER GDEM 130 km so e regional mperatures he summer d valleys ref a and the l Narmada R and Royce ough Middl 980) and M 7), before e (Morad et about 30-3 hout its his lected in ch the map rep is a product uthwest of climate is s > 40 °C), monsoon f lect the inte ongest of t iver, along , 1982). Or e Proterozo iddle-Plei turning e al., 1991). T 5 m, form tory, the pa anges in its 79 resent the of METI Varanasi, in ub-tropical and cooler rom June to nse summer he southern the line of a iginating in ic limestone stocene and astwards to he modern ing deposits ssage of the flood-plain , 80 deposition and channel down cutting), since the river is constrained laterally by its geological setting (Sharma and Clark, 1983; McMenamin et al., 1983). The area of study includes river-cut cliffs in the alluvial zone between the confluence of the Rehi and Son rivers and Khunteli (or Khuteli) (Figure 5-1). The reported YTT deposits (Acharyya and Basu, 1993; Jones and Pal, 2005) comprise a discontinuous tephra bed covering an area of ~ 90 km2 ranging in thickness from 20 cm to 3–4 m. Between Rehi and Ghoghara (first described by Williams and Royce in 1982), lateral variations within the ash deposits are minimal, and the ash unit appears repeatedly at a height between 4 and 6 m above the present river bed in cliff exposures. The Son river alluvial basin includes terraced surfaces flanked by floodplains, and point-bar and alluvial fan deposits. The main river channel is bounded by a series of Middle and Late-Pleistocene and Early-Holocene 10 to 30 m thick terraces, and deeply-incised seasonal channels known as ‘nalas’. The terrace incised by the modern Son has been intensively studied because of the presence of the YTT marker interstratified in the preserved fluvial sequence, as well as the coincidence of Middle Palaeolithic and Neolithic artefacts recovered from the sediments below and above the ash (Williams and Royce, 1982; Sharma and Clark, 1983; Williams and Royce, 1983; Jones and Pal, 2005; Jones and Pal, 2009; Haslam et al., 2010). The geological context of the terrace is unclear, mainly due to the absence of dates and robust stratigraphic correlation (Mandal, 1983). The first study of the geomorphological succession and alluvial sequences of the Middle Son Valley was carried out by Williams and Royce (1983). A detailed geological survey was undertaken after the discovery, in the 1970s, of 334 localities yielding archaeological artefacts ranging from the Lower Palaeolithic to Neolithic periods (Sharma, 1980: 88-115). The Son Valley alluvial sequence has been subdivided into four formations (Table 5-1). In chronological order (oldest to youngest) they are: the Sihawal Formation, Patpara Formation, Baghor Formation and Khetaunhi Formation (Williams and Royce, 1982; Williams and Royce, 1983; Williams and Clarke, 1995; Williams et al., 2006). Several models have been proposed for the geomorphological evolution of the alluvial plain of the Middle Son Valley ranging from the early Pleistocene to the late Holocene (Williams and Royce, 1982, 1983; Williams and Clarke, 1995; Williams et al., 2006). 81 In their initial geomorphological model, Williams and Royce (1983) proposed that the aggradations of the floodplain started with the accumulation of non-fluvial colluvium (the Sihawal Formation), ~ 100 ka ago, followed by the aggradation of Patpara (~ 30 ka ago). During this period the river shifted to a low sinuosity bed-load regime and created a + 25 m high terrace. Following this phase of aggradation and incision, the river accumulated the sediments ascribed to the Baghor Coarse member, dated ~ 18 ka, maintaining the same style it had during the accumulation of Patpara. A drastic change has been suggested during the accumulation of the Baghor Fine member, (dated ~ 13 ka), during which the Son moved to a narrow, deep suspended load-dominated regime. More recently, Williams et al., (2006) introduced a new unit between the deposition of the Sihawal and Patpara called the Khunteli Formation, dated ~ 58 ka (Table 5-1). The introduction of this new formation led to a new geomorphological model (Williams et al., 2006). In this model the authors suggest five major phases of aggradation at ~ 90 ka, ~ 73 ka, 58-45 ka, 39-16 ka, and 5.5-3.5 ka. These periods corresponded, respectively, to the deposition of Sihawal, Khunteli, Patpara, Baghor and Khetaunhi Formations. The phases of aggradation were said to correspond broadly to phases of colder and a drier climate, with weakened summer monsoon regimes, while river incisions corresponded to periods characterised by strong summer monsoons and high river-discharges (Gibling et al., 2008). 82 Table 5-1 Quaternary alluvial stratigraphy of the Middle Son Valley. Formation Type-section Description Chronology Reference Khetaunhi 1 km upstream from the Rehi-Son confluence, on the right hand side of the river. Alluvial sands and clays 5,305 -3,215 yr BP by 14C on shell and charcoal (Williams and Clarke, 1984); 6.3 – 3.2 ka calibrated radiocarbon (Pal et al., 2005) Williams and Royce, 1982; Williams and Royce, 1983; Williams and Clarke, 1984; Williams et al., 2006. Baghor South side of the Baghor village Two-member formation: coarse unit (Baghor Coarse), characterised by large-scale sandwaves and a finer upper member (Baghor Fine) made of overbank fine sands and silts Baghor Coarse: ~ 24– ~ 39 ka ; Baghor Fine: ~ 19 ka (Pal et al., 2005; Williams et al., 2006) Williams and Royce, 1982; Williams and Royce, 1983; Williams and Clarke, 1984 Williams et al., 2006. Patpara The archaeological site of Patpara, near the Patpara village Alluvial sands, clays and gravels with clasts in the range from sand to cobbles 100 – 30 ka (Williams and Royce, 1983); ~ 58 ka (Williams et al., 2006). Williams and Royce, 1982; Williams and Royce, 1983; Williams and Clarke, 1984; Williams et al., 2006. Khunteli On the right hand bank of the Son, near the village of Khunteli, and on the left bank of the river Son near its confluence with the Rehi river Basal unit of unconsolidated medium sand, a discontinuous bed of volcanic ash, cross- bedded and planar- bedded medium and coarse sands and fine gravels; an upper unit of carbonate cemented gravels ~ 74 ka (Williams et al., 2006) Williams et al., 2006. Sihawal Village of Sihawal, 1 km east of the archaeological site of Sihawal Non-fluvial clayey gravels and gravelly clays ~ 100 – 90 ka (Williams et al., 2006); ~ 130 – 137 ka (Haslam et al., 2011) Williams and Royce, 1982; Williams and Royce, 1983; Williams and Clarke, 1984; Williams et al., 2006. 83 5.3 Methods The aim of this chapter was to assess the validity of the tephra as a stratigraphic marker. In an attempt to correlate the tephra layer across sections, 30 km of the river bank exposures were surveyed, logged and sampled (see §2.1). Serial photographs of cliff sections were taken from boat and bank traverses, and photomosaics were constructed to aid the contextualisation of the YTT layer in the stratigraphy. The modern topography was surveyed using a Total Station (Zeiss Elta R55 EDM). The 600 points obtained were interpolated using the software Surfer 3.0 and ArcMap (Figure 5-2) that provided a further means of investigating the distribution of the tephra. Nine sections exposing volcaniclastic sediments were discovered and surveyed during the 2009 fieldwork (Table 5-2). Six sections were logged and their sedimentological structures described in terms of depositional facies (Table 5-2). Two of these sites, GG1 and KH, have been previously described (Williams and Royce, 1982; Jones and Pal, 2005; Williams et al., 2006; Jones and Pal, 2009; Jones, 2010). The six sites were selected on the basis of their exposure, ash characteristics, sediment structures and spatial distribution (Table 5-2). In order to isolate the depositional environments in which the tephra was identified, the sediments have been assigned facies and floodplain associations using the codes proposed by Nanson and Croke (1992) and Miall (1996), respectively. The major facies assemblages and the depositional settings prevailing at the time of the ash deposition were identified. This led to a geomorphological model for the dynamic activity of the river during the critical period of interest. 84 Table 5-2 List of the sites investigated during the 2009 field campaign. Type Site Locality Coordinates Lit. Thickness primary ash (cm) Thickness secondary ash (m) Selection criteria P R IM A R Y + SE C O N D A R Y A SH RH1 Rehi 24°30’9”N 82° 0’ 56”E N/A 5 1.6 Western site GG1 Ghoghara cliffs (Main Site) 24°30’7”N 82° 1’ 2” E Williams and Royce, 1982 5 1.5 Main ash site, firstly discovered GG1. b Ghoghara cliffs (gully) 24°30’7.5”N 82°1’2.99”E N/A 2-5 1.05 Sediment structures GG2 Ghoghara cliffs 24°30’10”N 82° 1’ 8”E N/A 0.1 (disturbed lenses only) 0.90 / GG3 Ghoghara cliffs 24°30’8”N 82° 1’ 9”E N/A 0.45 (disturbed) 1.4 / GG4 Ghoghara cliffs 24°30’7”N 82° 1’ 11”E N/A 0.1-0.4 2.28 Eastern site GG5 Ghoghara cliffs 24°30’14”N 82°1’20.6”E N/A disturbed lenses only ~ 1 / N/A SE C O N D A R Y A SH O N LY RH2 Rehi confluence 24°30’6”N 82° 0’ 55”E N/A / 1.3 Western secondary only site KH Khunteli 24°32’28”N 82°16’ 33”E Acharyya and Basu, 1993 / 2.2 Situated on the right side of the river Figur the m e 5-2 Sites and po orphology of the r sition of YTT ash iverside cliffs and at Ghoghara. The the position of the topographic profil ash sites Rehi 1 (R e was derived from H1) and Rehi 2 (R a survey carried H2). out with a Zeiss Elta R55 EDM total station. The phot 85 omosaic shows 86 5.3.1 Criteria for discriminating primary ash fallout and reworked tephra deposits For this work, sites were selected that represented primary and/or reworked ash, and considered textural, sedimentological and stratigraphical characteristics of the ash and its associated sediments. Primary (unreworked) ash-fall is characterised by: i) its whiteness (Munsell code 7.5YR or 10 YR 8/1 or 8/2); ii) thickness ranging between 4–5 cm; iii) sharp lower contact with siliciclastic sediments; and iv) homogeneous texture. Secondary (reworked) ash deposits are characterised by: i) either massive or with post-depositional structures (cross-bedding, root casts, bioturbation); ii) discontinuous/mixed contacts with units above/below, and iii) geomorphological features indicating displaced facies (including blocks of ash within older sediments, traces of slumping, etc). Further details on the differences between primary and secondary ash can be found in Chapter six (Table 6-4). 5.4 Tephrostratigraphy 5.4.1 Primary and secondary ash sites The sites lie within an area between the Rehi-Son confluence and the cliff on the northern bank of the Son river (Figure 5-2). Excavations here demonstrated that the sites in which primary ash was identified all present a similar stratigraphic sequence (Figure 5-3). The sections include 2–8 m of cross-bedded brownish medium sand (Facies Scp), a 5 cm clay bed (Facies Cl) at the base of the sections and 1-3 m of micaceous coarse silt (Facies Smc) enriched in calcrete on the top of the sequence, capped with soil (Facies P). The ash horizon can be distinguished within all the studied sections, but only three provide important tephrostratigraphic markers: sections RH1, GG1 and GG4. These horizons consist of a 2–8 cm thick stratum of primary ash (Facies PA), the base of which is always sharp on the underlying clay, and 1-2 m thick unit of reworked ash (Facies SA) gradationally overlying Facies PA. The primary ash is characteristically powdery in texture, comprises finer grains and is white (10YR or 7.5YR 8/1 and 8/2). The secondary ash is texturally coarser, darker (10 YR 8/3 or 7/1) 87 and appears in massive beds with no apparent internal depositional structures. The ash sequence gradually coarsens upwards and the contact between the secondary ash and the siliciclastic silt is indistinct. Table 5-3 Lithofacies codes and description, association and interpretation (after Miall , 1996). Lithofacies Code Colour Description Architectural Element Stratigraphic position Type-section Palaeosol P 7.5 YR 7/4 Pedogenetically altered, oxidised sediment enriched in calcretes+ and roots. Distal/abandoned Above ash Everywhere Micaceous massive silty sand with calcretes Smc 10 YR 6/6 Massive unit of heterogeneous sand mixed with micas and silt. Calcrete nodules and roots. Above ash Everywhere Secondary ash SA 10 YR 8/3, 7/1,7/3, 7/4 Volcaniclastic silt, mixed with sand; usually finely laminated, coarsening upward. Overbank Above ash Everywhere Primary ash PA 10 YR 8/1 Very fine ash, compact and without fluvial structures. Ash RH1, GG1.a, GG1.b, GG4 Coarse Clay with roots/calcretes/sand Csc 10 YR 4/3 Massive clay mixed with sand or silt, enriched in calcrete nodules and roots. Below ash RH2 Massive coarse clay with mudcracks Cm 10 YR 4/3 Massive clay. Below ash RH2 Laminated fine clay Cl 10 YR 7/4, 5/4 Clay mixed with sand, presenting fine horizontal lamination Below ash RH1, GG1,GG1.b, GG4, KH Cross-bedded pebbly sand Scp 7.5 YR 6/4 10YR 6/3, 6/6 Poorly sorted planar cross-bedded medium to find sand; horizontal laminations, imbricates pebbles, shale grains. Lateral accretion Below ash, near the present channel bed RH1, GG1,GG1.b, GG4, KH 88 Figure 5- (GG4) an 3 The princip d C) Rehi 1 (R al ash sites of H1). the Rehi-Ghoghara location: A) Ghoghara 1 (GG1); B) Ghoghara 4 5.4 The (Fig (Fac latte (~ 1 (Fac with volc unit bedd fine unit the sedi sand the l F l .2 Sites s two seque ure 5-4). Th ies Cm); len r becoming .3 m thick ies Smc). T the primar aniclastic r . KH (Figur ed sand se bands of cl is capped b latter, 1-c mentologica . The unit i ower sand u igure 5-4 Sit (RH1) and B) ayer is only v howing on nces that p e RH2 secti ses of grave coarser and ) is intermi he Munsell y and secon eworked un e 5-4b) is st en at the ba ayey silt, 2- y a fine str m thick a lly similar t s yellowish nits and th es containing Khunteli (KH isible at the to ly reworke resented re on (Figure l, in which carbonate- xed with th colour of t dary sequen its. Again, ratigraphica se of the sec 3 cm thick: atified sand nd mixed o a 2-m len brown in co e clay, their secondary as ), 30 km dow p end of the s d ash worked ash 5-4a) is com a mixture o rich toward e same mi he secondar ce, it appea no sedimen lly similar t tion (~ 8 m 11 m above unit and a with clay. s of volcani lour (10 YR origin is un h only. A) Re nstream from ection, and is show par posed of da f fine sand s the top (F caceous silt y ash of RH rs that RH2 tary structu o section G thick). The the river b thick carbon The seco clastic mate 5/4). Altho certain. hi 2 (RH2), n Ghoghara, substantially ticular strat rk brown c is also obser acies Csc an that overli 2 is 7.5YR represents res are rec G1, since it cross-bedd ed, the cros ate band. A ndary ash rial mixed w ugh fine lam earby the pri on the Son’s reworked. igraphic ch arbonate ce ved within d P). The re es the othe 7/4 (pink) only the fina ognised wit exposes the ed sand alt s-bedded m thin ash la unit at K ith clay an inations ap mary ash site south bank. T 89 aracteristics mented clay the clay, the worked ash r sequences . Compared l part of the hin the ash same cross ernates with edium sand yer overlies H appears d laminated pear within of Rehi 1 he tephra - 90 5.4.3 Tep The majori structures in Ghoghara m layer that ca it is 1.5 cm darker cont it is a 1 cm white (5YR bioturbated reworked as Figure 5- The unit is like laminat bands, 1 to hra sedim ty of the te the upper ain section n itself be s thick, white act; it is 2.5 thick lens of 8/1) powd palaeosurfa h deposits. 5 Primary ash characterise ions, group 3 mm thi entologica phra depos reworked t . This site ( ubdivided in (7.5YR 8/ cm thick, p darker ash ery ash, vi ce, ca. 1 m layer and rew d by severa ed in cm-t ck, and thi l structure its in the S ephra layer Figure 5-5) to four sub 1), powdery inkish white , including m sually very m thick. Th orked sequen l sedimenta hick bands, cker paralle s and geo on valley s s. The exce exposes ~ 8 -units: 1) as ; 2) ash 2, o (7.5YR 8/2 edium san similar to e palaeosur ce in GG1.b. ry structure repeated c l bands. Th metry how no ev ption is site cm basal as h 1, in direc n the top o ,); 3) ash 3, d grains im ash 2. Ash face is shar s (Figure 5 yclically eve e volcanicl idence of s GG1.b, in h, revealing t contact w f ash 1, div located on purities; 4) 4 is overla ply overlain -5): ~ 1-2 m ry 10 cm; astic comp edimentolo a gully near a ‘primary ith the clay ided by a sh the top of a ash 4, ~ 3 cm in by a he by 1.5 m t m thick rip light-dark w onent gradu gical the ’ ash unit; arp sh 2; of avily hick ple- avy ally 91 decreases towards the top of the sequence. No traces of post-depositional disturbance (i.e. slumped blocks, roots, rhyzoliths, or carbonate nodules) are found within the ash. 5.5 Discussion Although the ash at sites GG1 and KH have been studied since the 1980s, examination of the taphonomy of the ash units has been minimal (Williams et al., 1996, Jones, 2007; Williams et al., 2009). To date, the ash of GG1 has been described as ‘well preserved’ and ‘80 cm relatively pure’ (Jones and Pal, 2005), ‘compact’ (Jones, 2010), ‘discontinuous bed of pure volcanic ash up to 1.5 m thick’ (Williams et al., 2006), and ‘laterally discontinuous unit of volcanic ash up to 4 m thick’ (Williams and Royce, 1983). The reworked ash has received less attention, being described only by Williams et al. (2009) as ‘completely cemented with carbonate from 3.45 to 3.83 cm above the base of the ash’ in the Ghoghara section, while ‘the upper 70 cm of the ash is reworked’ in Khunteli (Williams et al., 2009). The facies reconstruction (Table 5-3) allows discussion of the stratigraphical characteristics of the YTT in their sedimentary context, thus demonstrating how ash facies associations can unravel the dynamics of a river depositing, redepositing and preserving the tephra (Macklin et al., 2002; Lewin et al., 2005; Bridgland and Westaway, 2008). These features should be considered carefully if a tephra layer is to be used as a chronostratigraphic marker. 5.5.1 The local environment pre- and post-deposition of the YTT in the Middle Son Valley The lithofacies assemblages identified represent specific styles and sub-environments of deposition within the river catchment. Figure 5-6 shows the stratigraphic units of the six type- sections, the corresponding facies and their lithofacies association. 92 Figure 5-6 Tep YTT sequence horizon (Stoll hra type-section around this area hofen et al., 2008). logs. The facies as is remarkably sim sociation between ilar, suggesting th Rehi and Khuntel e requirement of p i offers an insight articular environm into the morpholo ental niches for t gy and activity of he preservation of the river around the primary volca 74 ka ago. The nic ash fallout 93 The sedimentary structures within this facies (cross-lamination, imbrication, poor sorting) indicate that the sand was deposited on a point-bar or counterpoint-bar (cf. Miall facies code, Miall, 1996). The medium grained, cross-bedded sand observed at all the sites at the base of the succession (except RH2 and GG1.b) suggests proximity to the active channel. These characteristics indicate a large-scale depositional environment of lateral accretion from the main river channel, similar to the bar accretions observed in the Narmada river, Gujarat (Khadkikar, 2003). The river eroded on one side of the channel and deposited its finer sediments on the other side, creating point-bars and shallow-water deposits. Facies Cl suggests a distal, shallow-water, low-energy environment. This is consistent with the presence of very fine, powdery volcanic ash overlying this clay. Both Facies PA and SA also suggest a low energy aquatic environment, favourable to preservation of the deposits. The facies association characteristics suggest an overbank environment, established prior to ash deposition. Facies Smc and P are characterised by coarser silt, pervasive pedogenic features and carbonate nodules. The presence of carbonate nodules and roots clearly indicates a cessation of fluvial activity, and the facies association may represent an abandoned terrace surface, or distal deposits that the river was unable to reach even during floods (Simonsen and Toft, 2006). These multi-facies associations indicate a fluvial floodplain setting consisting of ephemeral ponds and oxbow lakes isolated from the main channel through point-bars and floodplain surfaces, where the ash could be preserved. This is consistent with microanalyses of the tephra units in the Ghoghara and Khunteli sections conducted by Jones (2010), which highlighted a distinct difference between the particle-size distribution of the primary ash (~ 60 μm) and the upper secondary ash layer (> 125μm), thus suggesting the primary ash was deposited into an aquatic environment. Figure 5-7 shows the lateral accretion and deposition on the point-bar of coarse sediments (gravel-size), the deposition of medium sediments in the near-channel overbank environment (medium and fine sand-size), and the accumulation of fine sediments in the distal overbank areas (silt and clay). 94 Figure 5- the main point-bar arrow ind of the as system re fluvial se floodplain during se a gradual protected its origin iii) repre subseque preserved 7 a) Generalis active channe ; overbank d icates the late h-fallout; c) l aching a new diments. Cas , with the ash asonal floods accumulation location, but al context, bu sents the ash nt to the river as primary d ed macroscal l is shown on eposits fill a ral aggradati ate-stage evo equilibrium es i), ii) and deposited in , bringing onl of fine rewo exposed to re t the upper co exposed in action. In th eposit. e model of a p the right; la shallow-lake on of the rive lution of the . c= coarse flu iii) indicate a low-energy y the finer se rked ash. Cas working. In t ntact might a secondary-d is case the YT oint-bar-cha teral accretion at left of the r; b) hypothet ash deposits vial sedimen three possible environmen diments. In th e ii) represen his case the p have been par eposition sit T will show s nnel in a low deposits are point-bar, in ical river geo , with the as ts; m=medium scenarios. C t, where the w is case prima ts the case of rimary ash m tially eroded e. Ash reach trong signs o -to-medium s shown on th the floodpl morphology a h incorporate fluvial sedi ase i) is the ater can reac ry ash is pres ash preserved ight have bee and redeposi ed the site fr f reworking a inuosity river e flanks of th ain; the green t the momen d in a fluvia ments; f= fin case of dista h the ash only erved beneath in a relatively n preserved in ted after. Cas om upstream nd will not b ; e t l e l e , e 95 As a result of the lateral accretion-aggradation style in this area, the river deposits its sediments laterally and not vertically (Figure 5-7a: note the arrow indicating the preferential aggradation direction). In such a setting, following the eruption, primary ash would have been preserved only in protected low-energy niches that were rapidly buried by later sediments. The remaining ash, especially if left exposed at the surface, would have been rapidly eroded to be re-deposited downstream or in lateral channels (Németh and Cronin, 2007). The progression from lateral accretion to overbank to abandoned terrace environments apparent in the Ghoghara section suggests a gradual shift in the river morphology. This change in depositional style is reflected in changes in the grain size of the deposits (from medium sand to silt) that are typical of fining- upward fluvial sequences: the river fills the channel and its active bed shifted laterally further south. 5.5.2 YTT deposits in the Middle Son Valley as a chronostratigraphic marker? Several attempts have been made to place the YTT within the broader alluvial stratigraphy of the Son Valley, in order to reconcile the history of the alluvial plain with the archaeological artefacts. Review of the literature leaves the exact stratigraphic position of the YTT bed in relation to the Quaternary formations unclear. The YTT has been placed within the Baghor Coarse Member (Williams and Royce, 1982; Basu et al. 1987; Acharyya and Basu, 1993), beneath the Baghor Coarse Member (Williams and Clarke, 1995), at the junction between the Patpara Formation and in the Baghor Coarse Member (Jones and Pal, 2005; Jones, 2010). More recently it has been proposed that the tephra lies between a newly described Khunteli Formation, dated to 73 ka, and the Patpara Formation, with an age of 56 ka assigned to the latter (Williams et al., 2006). Here it is suggested that these inconsistencies are related to the assumption that the tephra bed always occurs in its correct (i.e. primary) stratigraphic position and the lack of dates in direct association with the tephra sediments. Furthermore, the geomorphological model indicates that river aggradation has tended to create a lateral discontinuity that disturbs the vertical accumulation; therefore assigning the ash to a specific vertical unit could be misleading. 96 5.5.3 Reliability of the YTT as palaeoenvironmental marker A more recent study (Williams et al., 2009) also focused on the Rehi and Khunteli sections, in an attempt to gain insights into the environmental impacts of the YTT eruption. In this work, carbon and oxygen isotopic ratios were measured in calcareous nodules and root casts found below, within and above the ash sampled from the GG1 and KH sites. The results suggested replacement of C3 forest that had thrived prior to the YTT fallout by C4-dominated grasslands or wooded grasslands afterwards. They concluded that the YTT eruption led to these changes. Similarly, Jones (2010) considered the silt-dominated facies overlying the ash a sign of abrupt climatic change immediately after the eruption. While the time-frame and pace of aggradation of the post-tephra units, together with the time of restabilisation of the system, cannot be determined only using stratigraphy, it is also notable that there is no evidence that the units overlying the ash were deposited immediately after the eruption. The model proposed here implies that the river deposits at Ghoghara and Khunteli were exposed to erosion and reworking, such that the stratigraphy of the ash deposits could result from incision, lateral erosion and redeposition on a timescale of weeks to decades (i.e. Lawrence and Ripple, 2000; Todesco, 2004; Zobel and Antos, 2007), to centuries (i.e. Telford et al., 2004), to millennia (i.e. Lotter et al., 1995). The silt-dominated facies overlying the ash is widespread on the top of all the Middle, Late Pleistocene and early Holocene terraces. The post-Toba floodplain silt facies could indicate either that the dynamics of the river channel changed substantially following the eruption (suggesting a strong post-Toba environmental and climatic effect), or that the coarse/medium sand above the ash layer is no longer preserved. The latter could indicate by contrast a migrating channel and change in facies, suggesting a major geomorphological impact on the river rather than eruption-related climatic changes. The major problem in tackling the palaeoenvironmental impact of the Toba super-eruption is that existing methods of palaeoenvironmental reconstructions lack the analytical precision needed to answer the time-scale issue (Williams, 2012b). Moreover the sedimentation rate in fluvial environments lack the temporal resolution needed to address questions regarding climate change after the YTT eruption (Paredes et al., 2007). The Ghoghara site GG1.b, at which fine 97 stratification indicates a slow sedimentation rate, appears to be the one locality suitable for chronology-critical work. 5.5.4 Reliability of the YTT as an archaeological marker Archaeological studies (Jones and Pal, 2005; Jones, 2007; Jones and Pal, 2009) have attempted to establish associations between the ash and the Palaeolithic artefacts in the Middle Son Valley deposits. It is noted that artefacts have not been recovered from stratigraphic units that show clear evidence of YTT primary ash and the time at which evidence of human populations reappeared may be in the order of millennia (given the uncertainty of the dating methods previously employed, see Jones and Pal, 2009). It has been demonstrated that the evidence of reworking at many of the Middle Son Valley sites, suggesting that the chronological relationship between the artefacts and the YTT strata in the Son Valley is insufficient to allow a robust connection between the eruption and its human impact. The palaeogeomorphology of the area suggests that new archaeological sites in association with primary YTT horizons might be found closer to the interior of the fluvial plain, towards the Rehi River. 5.6 Conclusion The lithofacies associations from the Rehi-Ghoghara-Khunteli sites presented here have revealed an environment conducive to the preservation of primary ash fallout. Nevertheless, the YTT ash was preserved only in selected geomorphic environments that offered protection to the unconsolidated volcanic particles. This environment was a low energy, shallow-water depression near the main river channel. Before the YTT fallout, the Son River had adopted the characteristics of a sand-dominated, medium-sinuosity and low-gradient river, with laterally stable single channel, seasonal floods, floodplains and point-bars. The fining-upwards sequence (reflected in the shift from lateral accretion to overbank and distal channel) could represent the gradual filling of the river-bed due to meander migration. The stratigraphic context of ash deposits in the Middle Son valley is rarely of the quality required to provide a well-defined chronostratigraphic marker horizon. The ash units often show 98 abundant evidence of reworking, with an upper boundary in gradational contact with the overlying silts. Out of 30 km of river bank surveyed (on either side of the river), only one localised occurrence where the ash could be considered ‘primary’ in context was found, and neither of the ash locations corresponded to a co-location of archaeological artefact assemblages. It is therefore critical that sampling for dating and palaeoenvironmental reconstructions take full account of the sedimentation style and morphology of the river and the associated evolution of the local landscape over the period. The next chapter focuses on this issue, using particle size analyses, magnetic susceptibility and scanning electron microscope images to analyse the mechanisms of accumulation and preservation of reworked deposits in Malaysia, ~ 390 km from the vent. The micro-scale analyses allow further exploration of the mechanisms theorised in this chapter, revealing site-specific processes that radically modify the stratigraphy of the tephra beds and have primary control of the ash characteristics. 99 Chapter 6. Depositional processes and sedimentology of YTT deposits in the Lenggong Valley, Malaysia Based on Gatti et al. (2012). Abstract Chapter six builds on the discussion of chapter five, analysing in detail the characteristics of reworked tephra and reconstructing the mechanism of deposition and accumulation of distal deposits. It will show that the taphonomy of the tephra can be interpreted in terms of environment of deposition and mechanisms of reworking, and that these factors are fundamental to assessment of the relevance of the ash to chronostratigraphic and palaeoenvironmental reconstructions. The chapter presents a study of the characteristics and depositional processes of four newly discovered deposits of the YTT in the Lenggong valley, Malaysia. It focuses, in particular, on site stratigraphy, sample particle-size distributions, magnetic susceptibility and mineralogical associations. Reworked tephra display variable sedimentological characteristics: polymodal and unimodal, very fine to coarse grained distributions, variable percentages of ash ranging from 70–99% in the main size fraction (63-125 μm). It is found that particle-size distributions from this study are similar to those of published analyses for primary YTT deposits, demonstrating that particle size alone cannot distinguish primary from secondary tephra deposits. The reworked YTT tephra from Malaysia are associated with fluvial and colluvial transport and deposition. Three volcaniclastic facies have been identified corresponding to flood-flow, mudflow and slumping sedimentation. The evidence suggests that the ash accumulated rapidly, over a period of a few days to months, and was quickly buried. In this valley, the ideal site for palaeoenvironmental reconstructions is Kampung Luat 3, where ash accumulated on a vegetated floodplain and at least two distinct phases of sedimentation are represented. Despite the rapid accumulation, these sites are not well suited to palaeoenvironmental study of the YTT impacts. This has wider implications for palaeoenvironmental reconstruction based on reworked tephra sequences. 6.1 Introduction Distal tephra deposits can be used to correlate a wide variety of palaeorecords over ranges of up to thousands of kilometres (Sarna-Wojcicki et al., 1985). Tephrostratigraphy and tephrochronology, including the study of microtephra, therefore represent an important complement to palaeoenvironmental (ie. Zanchetta et al., 2011; Narcisi and Vezzoli, 1999; Froese et al., 2006; di 100 Rita et al. 2009) and archaeological reconstructions (Petraglia et al., 2007; Petraglia et al. 2009; cf. Chapters four and five) because they are capable of providing easily-identified, isochronous markers (Sarna-Wojcicki and Davis, 1991; Alloway et al., 2007; Lowe, 2011; Davies et al., 2012). However, before being used in this way, their integrity should be carefully assessed. Only primary deposits (i.e. in situ ashfall deposits) should be used for chronological reconstructions, since only ash immediately deposited after the eruption can guarantee temporal continuity between the strata. Distinguishing primary from secondary deposits (i.e. those arising from reworking of primary ash materials) is therefore a fundamental step prior to assuming that encasing sediments represent pre- and post-eruptive periods. To this end several solutions have been proposed. For example, Morley and Woodward (2011) used micromorphology to distinguish between primary and secondary deposits. Using a combination of grain counting and micro-scale structures, they suggested that the higher content of ash grains, the absence of fluid reworking and vertical structures, together assisted in determining whether or not the ash was in primary context. Jones (2010) studied the particle-size distributions of primary and reworked ash units at Jwalapuram in India. She noticed that the lowermost primary ash was finer-grained than all other ash samples, and suggested that such a particularly fine-grained composition resulted from sorting of the ash fallout during gentle redeposition into an aquatic environment. Generally, in the majority of studies the differences between primary and secondary ash are assessed through a combination of micro-scale and macro-scale semi-quantitative observations, adapted to each case. While reworked deposits may not provide reliable temporal markers, they can still be valuable in palaeoenvironmental studies, such as in the investigation of the environmental impact of ash fallout on the receiving environment. Proxies including pollen, phytoliths, benthic organisms and geochemical traces from sediments have been used in assessing post-eruptive environmental changes (Schulz et al., 1998; Margari et al., 2007; Williams et al., 2009; Haslam et al., 2010). However, before reworked tephra deposits can be used in palaeoenvironmental studies, it is vital to understand and reconstruct their depositional history and transport pathways. 101 Traditional environmental records provided by geochemical and palaeontological proxies are usually extracted from high-resolution sedimentary sequences that have established temporal records, such as lake beds, varve and loess (Lowe and Walker, 1984). In the case of tephrostratigraphical sections, the resolution of sediments deposited is too low to be distinguished temporally (Williams, 2012b). The question is therefore whether environmental proxies can reliably record environmental changes that occurred during and after the ashfall event. The first step in addressing this question is to understand the depositional pathway that resulted in the formation of the tephra unit, in order to select the best site for palaeoenvironmental reconstruction. Errors can arise where gaps occur in the episodes of accumulation as a consequence of non-deposition, local erosion and/or low sediment yields. The high variability of the sedimentological characteristics of the reworked tephra — even when the ash is deposited in the same environment — can further complicate the reconstruction of the reworking processes (Davies et al., 2007; Pyne-O'Donnell, 2011; Davies et al., 2012). This chapter focuses on these two issues, an attempt to distinguish between primary and secondary ash and an assessment of the mechanisms of tephra reworking. For this purpose, the research analyses four newly discovered Younger Toba Tuff (YTT) tephra exposures at Lenggong, in Malaysia (Figure 6-2), in addition to presenting new geochemical data on the glass shards that confirm that the tephra corresponds to the YTT. The aims are: a) to determine whether it is possible, using the methods presented, to distinguish between primary and secondary ash and b) to determine the most suitable site in the Lenggong valley for future palaeoenvironmental reconstruction. 6.2 Study Area The Lenggong valley (Figure 6-2) lies in the Perak district of north Peninsular Malaysia, 350 km from the Toba caldera. It is well known as a site of YTT tephra deposits (Scrivenor, 1930; Ninkovich et al., 1978a; Stauffer et al., 1980; Chesner et al., 1991; Mokhtar, 2009; Smith et al., 2011; Matthews et al., 2012). The most studied YTT site in the valley is Kota Tampan, where the ash has been used as an isochronous marker in assessing the age of the sediments and their associated stone tools. Here a 14C date of ~ 35 ka was obtained for the sediments immediately 102 underlying Ninkovich YTT, and th valley tephr Smith et al. has been ca known whe The Perak R Kelantan-Th a gently no Kampong K gradient of between th (Stauffer, 19 south Perak Stauffer, 19 (Middle Ple mud and pe Figure 6- sites in F NASA). the ash, th (1978a) cha us reinterp a have been 2011; Matth rried out on ther the YTT iver (North ailand bord rtheast to uala Bende ~ 0.8 m km e deeply di 72), throug comprise f 72): in asce istocene), t at (Holocen 1 Longitudin igure 6-2. Pro e latter incl racterised th reted the ag geochemic ews et al. 2 the nature ash at Kot -Western M er area (M southwest rok and th -1. The Leng ssected slop h which th our alluvial nding chro he Young A e). al profile of t files extrapol uding the T e ash by g e of the Ta ally charact 012), to the and geolog a Tampan i alaysia, Fi organ, 1973 sloping ter e Temengg gong valley es in the M e river has deposits th nological or lluvium (f he Perak Riv ated from AS ampan Pa eochemical mpanian to erised and authors' kno ical signific s a primary gure 6-1, F ). The river rain (Figur or dam, the is ~ 40 km ain Range incised. T at character der they ar rom the las er. Key locali TER DEM (A laeolithic to fingerprinti ols to ~ 75 identified a wledge no ance of the or reworked igure 6-2) r is ~ 400 km e 6-1). Bey Perak rive long and ~ Granite, a he overlyin ise the inlan e the Bould t interglaci ties are indic STER GDEM ols (Stauffe ng, confirm ka. Althoug s YTT (e.g. accurate str Lenggong t deposit. ises in the n long and is ond the a r has a rel 4–2 km w post-Trias g Quaterna d valley fil er beds, th al to presen ated and corr is a product r, 1973). L ing it to be h the Lengg Mokhtar, 2 atigraphic s ephra. Nor orthern Pe associated rtificial lak atively cons ide, constra sic acid plu ry sequence l (Walker, 1 e Old Alluv t) and Org espond to th of METI and ater, the ong 009; tudy is it rak- with e of tant ined ton s of 956; ium anic e Figure 6-2 the Malay by the dis the Lengg Map of the Perak sian counties of K sected hill slopes o ong valley. ASTER river region, nor elantan and Pahan f the Main range G DEM of the regio thwest Peninsular g, west by the Mal ranite (Stauffer e n obtained from G Malaysia. The Pe accan Strait, and s t al., 1972) and the DEM (ASTER GD rak region is boun outh by the Selang alluvial Quaterna EM is a product o ded at north by th or region. The Len ry sediments of th f METI and NAS e Thailand borde ggong valley is ge e Perak floodplain A). r and Kedah Coun omorphologically . Mt. Toba is ~ 35 103 ty, east by composed 0 km from 104 6.2.1 Geomorphological setting Four sites were investigated in 2010 (cf. Chapter two, Table 2-1). They lie near the village of Lenggong (5° 7’ 42.52’’ N, 100° 59’ 34.35’’ E), 60 km north from the capital of Perak Ipoh. The terrain is mostly covered by rainforest (Figure 6-3). The Kampung Luat sites lie near the main channel of the Perak river. Sites Kampung Luat 1 and Kampung Luat 2 (KgL1 and KgL2) lie, respectively, on the eastern bank of the river, 289 m and 212 m from the main channel, at 69 and 68 m a.s.l., 4 and 3 m above the main channel, now at the margins of an artificial lake (Figure 6-3a/b). The base of the ash was obscured, and the top truncated by modern soil. Kampung Luat 3 (KgL3) lies on a well-preserved fluvial terrace to the right of the main channel. The ash is preserved at an altitude of 71 m a.s.l., 115 m from the main channel and at 11 m above the Perak river bed. The ash units lie at the top of the fluvial terrace, exposed during a quarry excavation (Figure 6-3c). No deposits overlie the tephra at this site, the surface of the ash being colonised by dense rainforest vegetation. The unit exposed at Bukit Sapi (BTS) occurs at an altitude of 79 m a.s.l. The site is 4.70 m away from the main channel, 14 m above the river bed. This site is part of a small tributary stream valley incised into the north-western side of the Perak river valley. Neither the bottom nor top of the sequence could be seen because of the vegetation cover (Figure 6-3). F K igure 6-3 YT ampung Lua T sites in the t 3 (KgL3); d Lenggong va ) Bukit Sapi (B lley. a) Kamp TS). ung Luat 1 (KgL1); b) Kampung Luat 2 ( 105 KgL2); c) 106 6.3 Methods Ash samples were collected at different intervals, depending on the structures and type of sediments occurring within the sequences (§ 2.1). Facies interpretations are based on the depositional models of Nakayama and Yoshikawa (1997) and Kataoka (2005). Geochemical, particle-size and magnetic susceptibility analyses were executed following the protocols summarised in § 2.2.1, § 2.2.3 and §2.2.4, respectively. Additionally, single grains were subsampled using 1% of sieved fractions (< 32 μm, 63–125 μm, 125–250 μm, 250–500 μm; 500– 1000 μm), mounted on glass slides with glycerine and visually counted. Grains were classified as glass shards if they presented at least three tephra-like morphological features: crossed-polar full extinction, the presence of bubble walls/cuspid shape, an absence of refraction, sharp edges and absence of preferential crystallographic directions. Siliciclastic grains mainly comprised mica, quartz grains and undifferentiated clay mineral aggregates. Rare zircon and tourmaline were also present. 6.4 Results 6.4.1 Geochemistry Table 6-1 shows the geochemical components of the Lenggong tephra. The fingerprints of the tephra samples confirm the nature and origin of the Lenggong unit as ejecta from the YTT eruption. The glass analyses of the samples from the Lenggong sites resemble those from the YTT reported in the literature (Figure 6-4a). Minor differences between the new determinations and earlier data can be explained by use of different standards for calibration (as discussed in Chapter four, Figure 4-4). Similarly, rare earth element (REE) profiles of the Lenggong ash resemble the YTT REE profile reported in the literature (Figure 6-4). The results indicate relative enrichment in light REE, slight depletion of heavy REE and consistent, distinct negative Eu anomalies (Figure 6-4, Table 6-1). 107 Table 6-1 Major and REE elements of the Lenggong ash. Standard deviations given in brackets. wt% Bukit Sapi Kampung Luat 2 Kampung Luat 3 SiO2 74.88 (1.16) 74.62 (1.13) 74.07 (1.16) TiO2 0.05 (0.05) 0.04 (0.05) 0.05 (0.05) Al2O3 11.92 (0.29) 11.83 (0.32) 11.83 (0.29) FeO 0.87 (0.34) 0.87 (0.32) 0.83 (0.34) MnO 0.06 (0.08) 0.07 (0.08) 0.05 (0.08) MgO 0.06 (0.06) 0.07 (0.05) 0.06 (0.05) CaO 0.75 (0.09) 0.75 (0.12) 0.78 (0.09) Na2O 2.95 (0.19) 3.15 (0.22) 3.04 (0.20) K2O 5.13 (0.41) 5.03 (0.40) 5.07 (0.41) n 31 32 18 Total 96.67 96.42 95.78 ppm Bukit Sapi Kampung Luat 2 Kampung Luat 3 La 18.09 (2.4) 21.38 (6.6) 24.73 (4.1) Ce 37.76 (4.2) 49.37 (16.2) 50.21 (7.4) Pr 3.55 (0.5) 4.641 (1.6) 4.7 (0.7) Nd 12.56 (1.7) 16.85(6.0) 16.53 (3.0) Sm 2.32 (0.4) 3.69(1.5) 3.42 (0.8) Eu 0.28 (0.1) 0.29(0.1) 0.32 (0.1) Gd 2.17 (0.6) 3.12(1.6) 2.98 (0.6) Tb 0.39 (0.1) 0.63(0.3) 0.58 (0.2) Dy 2.40 (0.3) 4.077(2.2) 3.67 (0.8) Ho 0.53 (0.1) 0.95(0.5) 0.88(0.2) Er 1.60 (0.4) 2.84(1.4) 2.55(0.6) Tm 0.24 (0.01) 0.49(0.2) 0.44 (0.1) Yb 2.13 (0.5) 3.88(1.9) 3.29(0.9) Lu 0.31(0.1) 0.54 (0.2) 0.51 (0.1) n 15 10 14 108 Figure 6 fingerprin Smith et al. 2011, proximal those of d of the an reference -4 A) Major ts of identifi al. 2011 (Indi Chesner et a samples coll istal areas. Th alyses; B) Ra . Rare elemen chemical c ed YTT glass a); Shane et a l. 1998, Bedd ected from th is could be e re earth elem ts analyses fro omponents from literatu l. 1995, Smith oe-Stephens e e Toba calde xplained by th ents values m Smith et a of the Lengg re. Data from et al. 2011 ( t al. 1983 (S ra on Sumat e sample typ for the YTT l. (2011) ong ash co : Shane et al., Malaysia); W umatra). It is ra showed va e, indicated a Lenggong va mpared with 1995, Westg estgate et al. noteworthy lues differing s welded tuff lley ash and geochemica ate et al. 1998 1998, Smith e that the thre slightly from by the author the literatur l , t e s e 109 6.4.2 Stratigraphy All samples investigated, except for the siliciclastic units at the base of Kampung Luat 3, consist only of tephra. Kampung Luat 1 and 2 (KgL1, KgL2, 5° 03.360’ N, 100° 58.864’ E) lie on the opposite side of an artificial lake. Here the sandy tephra units (3.8 and 4.4 m thick, respectively) appear massive, and show few or no sedimentological structures (Figure 6-5a/b). No change in either units or lithology was apparent. The Kampung Luat 3 sequence (KgL3, 5° 03.833’ N, 100° 58.821’ E) is 3.7 m thick in total, and consists of a lower, 1.19 m thick siliciclastic unit (mainly clay and quartz), overlain by a 2.36 m thick volcaniclastic sequence of sandy ash with horizontal laminations (Figure 6-5c). The ash unit shows alternating light grey (10 YR 6/2-7/2) and grey (10YR 5/1) laminations. The lower siliciclastic and the upper volcaniclastic sediments are divided by a ~ 20 cm-thick lens, composed of oxidised brownish yellow (10 YR 6/8) sandy ash, and are delimited top and bottom by a 5-7 cm thick dark brown (7.5YR 5/8) very finely wavy laminated reddish clay (Figure 6-6). A fourth site, Bukit Sapi (BTS, 5° 08.776’ N, 101°01.398’ E) exposes a 3.7 m thick sequence composed of a massive, light brownish grey (10 YR 4/2) silty and sandy ash (Figure 6-5d). The ash outcrop can be visually subdivided into three ash ‘sub-units' separated by sharp contacts: 1) basal silty ash with clay component, ~ 1 m thick, light brownish grey (10 YR 6/2); 2) upper sandy ash, 2.20 m thick, dark greyish brown (10 YR 4/2), covered by soil and vegetation in the top 30 cm; 3), block of massive, compacted fine ash, 50 cm thick, white (10 YR 8/1), sandwiched between sub-units 1) and 2); the block is ~ 1.5 m from the bottom of the section. 110 Figure 6-5 Five EMP confirmed Schematic log of A analyses have b the association o the tephra sedime een obtained from f the tephra with th ntary sequences at the lower and u e Younger Toba T Lenggong valley. pper units of KgL uff. The tephra units a 2, 3 and BTS, and re the main sedim , in conjunction w entological compo ith LA-ICPMS R nents for all four are Earth Element sequences. s analyses, F f t b 6.4 Part susc 6-7. Tab min μm The Tab grad clus igure 6-6 Se inely laminat he developm y the river ov .3 Sedime icle-size dis eptibility (M The KgL1 Y le 6-2). The or silt comp (very coarse ash at KgL le 6-2). The ing. The se tered at 100 dimentary fea ed clay bands ent of a soil h erbank sedim ntology tributions f S) and pro TT ash sho particle-siz onent (34% silt - very f 2 is poorly analyses in diment at μm (very fi tures of the o limiting the orizon and e ents. or the Leng file-average ws modera e distributio ) and 2% c ine sand). to very po dicate high KgL2 is com ne sand, Tab xidised lens oxidised lens xtended suba gong valley d frequency tely sorted, ns indicate lay. The me orly sorted variability th posed of le 6-2). at the base of . The associat erial expositi samples ar distributio unimodal g a sand-dom an grain-siz , mainly un rough the 62% sand, the ash in K ion of iron o on of the terr e provided ns for each rain-size dis inated env e values ran imodal and vertical sequ 37% silt an gL3. Note the xides and clay ace, before in in Table 6- site are show tributions ( ironment (6 ge between bimodal (F ence, with d 1% clay, 111 dark red suggests undation 2. Magnetic n in Figure Figure 6-7a 4%), with a 57 and 100 igure 6-7b no apparen with means , , t 112 Table 6-2 Selected particle size distribution parameters for the Lenggong YTT ash. Grain-size distributions measured on Malvern Mastersizer 2000, data quoted as average of 4 analyses per sample. Mean particle size quoted as geometric mean following method of Blott and Pye (2001). Particle fractions are chosen according to ash grain-size classification divisions. Sample ID Mean (μm) Sorting (μm) 63-125 μm fraction of the total >250 μm fraction of the total Distribution Sorting KgL3-1 115.9 3.6 29% 28% Bimodal Poorly Sorted KgL3-3 93.13 2.9 47% 14% Unimodal Poorly Sorted KgL3-5 89.64 5.2 28% 29% Trimodal Very Poorly Sorted KgL3-7 77.17 3.5 40% 15% Unimodal Poorly Sorted KgL3-8 178.7 4.2 28% 29% Bimodal Very Poorly Sorted KgL3-9 51.04 3.3 49% 6% Bimodal Poorly Sorted KgL3-11 151.9 2.9 27% 34% Bimodal Poorly Sorted KgL3-12 123.8 5.4 24% 35% Trimodal Very Poorly Sorted KgL3-13 52.68 4.5 38% 12% Trimodal Very Poorly Sorted KgL3-15 59.17 5.0 29% 17% Trimodal Very Poorly Sorted KgL3-17 33.21 4.1 45% 4% Trimodal Very Poorly Sorted KgL2-1 121.2 4.8 25% 37% Trimodal Very Poorly Sorted KgL2-3 110.9 4.3 24% 33% Unimodal Very Poorly Sorted KgL2-5 59.35 5.2 27% 24% Bimodal Very Poorly Sorted KgL2-7 111.3 3.9 27% 30% Bimodal Poorly Sorted KgL2-8 46.96 2.4 65% 0 Unimodal Poorly Sorted KgL2-9 65.01 3.7 39% 11% Unimodal Poorly Sorted KgL2-10 81.75 3.9 35% 20% Bimodal Poorly Sorted KgL2-12 155.0 4.2 21% 46% Unimodal Very Poorly Sorted KgL2-13 74.36 4.1 37% 19% Bimodal Very Poorly Sorted KgL2-14 116.5 3.7 29% 30% Bimodal Poorly Sorted KgL2-15 78.29 4.5 31% 22% Bimodal Very Poorly Sorted KgL1-1 83.21 4.3 30% 21% Unimodal Very Poorly Sorted KgL1-3 71.92 3.5 44% 12% Unimodal Poorly Sorted KgL1-5 100.5 3.3 34% 20% Unimodal Poorly Sorted KgL1-7 68.51 3.5 44% 10% Bimodal Poorly Sorted KgL1-11 95.21 3.7 32% 22% Unimodal Poorly Sorted KgL1-13 78.52 3.3 41% 12% Unimodal Poorly Sorted KgL1-14 57.55 3.1 53% 5% Unimodal Poorly Sorted BTS-1 86.15 2.8 45% 5% Unimodal Poorly Sorted BTS-3 109.2 2.6 40% 17% Unimodal Poorly Sorted BTS 127.5 2.5 35% 20% Unimodal Poorly Sorted BTS-7 111.1 3.2 33% 20% Bimodal Poorly Sorted BTS-9 54.72 2.5 69% 0% Unimodal Poorly Sorted BTS-10 41.27 2.5 67% 0% Unimodal Poorly Sorted BTS-11 36.56 6.9 17% 19% Polymodal Very Poorly Sorted BTS-12 8.233 4.8 6% 1% Bimodal Very Poorly Sorted BTS-14 28.84 5.9 13% 15% Trimodal Very Poorly Sorted BTS-16 23.88 3.9 29% 7% Bimodal Poorly Sorted 113 The KgL3 sediments are polymodal, very poorly sorted and show substantial variations in mean particle sizes ranging from 51 to 178 μm (Figure 6-7c, Table 6-2). The BTS ash particle-size distributions range between 8 -127 μm. The sediments at this site show a higher clay frequency within the lower part of the section (Figure 6-7d). Moreover, this is the only site at which the silt component exceeds that of the sand (51% silt v. 47% sand, Table 6-2). Standard deviations indicate poorly to very poorly sorted sediments, with trimodal frequency distributions in the lower part of the section, but a unimodal distribution in the upper part. The ash at KgL2 and BTS is low in magnetic mineral content. The samples from KgL3, as expected, show a stronger magnetic susceptibility of the oxidised lens (9.3 10-8 m3kg-1), whilst KgL1 shows a weak magnetism at the level of the thin oxidised lens observed in sample KgL1-11 (6.4 10-8 m3kg-1), but also a strong magnetism in sample KgL1-5 (22.6 10-8 m3kg-1, Figure 6-7). All samples reveal an increasing magnetic susceptibility towards the top, arising from contamination by overlying soils. 114 Figur C) Se D) Se in ac e 6-7 A) Sediment dimentological ch dimentological ch cordance with the ological character aracteristics of Kg aracteristics of BT geomorphic reco istics of KgL1. The L3. The oxidised l S. BTS presents th nstruction of the particle-size distr ens is evident in th e finer grain sizes site, which indica ibutions of KgL1 e MS profile. High (2% clay, 51% silt) ted that BTS doe are skewed toward MS values towar . This is visible in s not belong to th s the coarser grain ds the top units ar the particle size di e same depositio sizes. B) Sedimen e probably sign of stribution, shifted nal environment o tological characte contamination by towards finer grai f KgLs but to a s ristics of KgL2. the upper soil. n size. It is also mall tributary. Tap asso amo ‘non have KgL cont (par and iden decr the Mic the F 6.5 The othe the honomic he ciations. In unt of ash -ash’ fractio substantia 1 (Table 6-3 ent of qua ticularly tho zircon, rep tified in Kg eases sharp clay hardpa roscopic an glass surface igure 6-8 A) Discus tephra unit r sites (Sha Lenggong terogeneity the 63–12 ranges betw n, the ash p l coarse frac ), at which rtz, zircon se from low resenting 5 L2-9. The K ly in the mi ns sandwich alyses of the s (Figure 6- Oxidised pati sion s of the Len ne et al., 199 ash was d of the Leng 5 μm inter een 59 to 9 ercentages tions (indic mineralogic , tourmalin er in the s 0 to 90% o gL3 ash is p ddle of the ing the ash ash grains 8). na on the sur ggong valle 5; Westgate erived from gong rewor val, consid 9 % (Table range from ated N/A in al compone e and mic ection) con f the non-a articularly v unit, before lens have in the oxidi face of KgL3 g y are geoch et al., 1998 the sam ked deposit ered the do 6-3). In the 36% to 89% Table 6-3) nts in the 6 a. In cont tain mica fl sh grains. M ariable: the again incre low ash con sed lens at K rains and B) emically sim ; Petraglia e e eruption, s is reflecte minant siz > 250 μm of the total . The site th 3–125 μm fr rast to Kg akes, togeth odern plan proportion asing towar tent (samp gL3 reveal Mica flake Kg ilar to thos t al., 2007; and assum d in their m e interval interval, con . A few sam at includes action also L1, the Kg er with a m t fragment of ash in th ds the top. A le KgL3-12, traces of iro l2. e reported a Smith et al. ing it wa 115 ineralogica for ash, the sidered the ples did no most ash is show minor L2 samples inor quartz s have been e sediments s expected Table 6-3) n oxides on s YTT from 2011). Since s deposited l t , . 116 contemporaneously, any difference between the sites (in thickness, mineralogy, grain size) should reflect post-deposition processes. Table 6-3 Ash content in the Lenggong valley tephra deposits. Site 63–125 μm ash fraction > 250 μm ash fraction KgL1-3 96% 71% Kgl1-5 92% 86% KgL1-7 96% N/A KgL1-11 94% 89% KgL1-13 95% N/A KgL1-14 99% N/A KgL2-3 77% 87% KgL2-5 84% 71% KgL2-8 77% N/A KgL2-9 89% 36% KgL2-12 77% 69% KgL2-15 74% 78% KgL3-3 93% 48% KgL3-5 59% 61% KgL3-7 78% 58% KgL3-8 93% 49% KgL3-11 92% 84% KgL3-12 22% 10% 6.5.1 Primary and reworked tephra: a reliable method of distinction? The exposed tephra deposits in the Lenggong valley present general taphonomic characteristics that reveal the reworked nature of the sediments: they are up to ~ 4 m in thickness, include structures such as wavy laminations and they have non-volcanic components that imply mixing with other sedimentary detritus prior to final deposition. No primary ash was found at the sites. A recent study of the primary ash layer in the Son Valley, India, showed a distinctive difference between the primary ash particle-size distributions - described as well-sorted, unimodal, with mean centred between 63 and 50 μm - and the reworked ash deposits above the primary stratum, characterised by polymodal distributions, poor sorting and presence of coarser particles (Lewis et al., 2012). Figure 6-9 shows a comparison of the particle-size distributions at Jwalapuram site 3 (Jones, 2010), and site KgL1. Jwalapuram exposes 5 cm of primary ash and 2.30 m of overlying reworked material. The plot shows that particle-size distributions of both the primary and reworked material from India and Malaysia are similar. The KgL1 samples are skewed to the right (very fine skewness), unlike the Indian samples. However, all the Indian tephra show a similar skew thro prim The (and sam non in d eith F t a M a In s unim ness, indep ugh plume ary ash. presence o thus an i ple KgL2-1 -volcanic gr istal tephra er during at igure 6-9 Pa ephra from th re similar. T alaysian rew sh data from ummary, if odality an endent of dispersion f coarser pa ndication o reveal that ains (Figur deposits, al mospheric t rticle-size dis e Lenggong v he primary orked tephra Jones (2010) the primar d high ash c their being in the atm rticles shou f reworking the larger g e 6-10). Ash though the ransport or tributions of alley. The pa ash sample ( . However, a . y facies can ontent can r primary o osphere, r ld not be ta ). Scanning rain-size fr particle ag process rem post- depos the primary a rticle-size dis in bold) is s sh aggregatio be seen in eliably be a r reworked ather than ken as an i electron m action is co gregation is ains only p itionally (Fo sh found at J tributions fro ymmetric an n could acco the field, pplied to su . Skewness provide a ndication o icroscope mposed of a widely r artially und lch et al., 2 walapuram s m the Indian d has a fine unt for such features suc pport the in may theref diagnostic f non-volca images of ash aggrega ecognised p erstood. It 010). ite 3 and the and Malaysia r mean peak a discrepancy h as mode terpretation 117 ore develop indicator o nic particles grains from tes and no henomenon could occur reworked n samples than the . Primary rate sorting (Table 6-4 f t , , 118 McLaren and Bowles, 1985; Klovan, 1966). However, these features cannot exclude the possibility that the ash is reworked: since as shown, secondary ash can be well sorted, fine and unimodal. This implies that where there is not a clearly exposed outcrop (for example in the case of cryptotephra in caves or lake cores) such techniques cannot be considered sufficiently robust to discriminate between the two (cf. also Davies et al., 2007; Morley and Woodward, 2011). Figur featu Photo e 6-10 Polymodal res to distinguish E shows a zoom ity is a typical ch between primary a on a 1200 μm aggr aracteristic of dist nd secondary ash egate: it is possible al tephra horizon . It is notable that to distinguish the s, due to the poor two of three peak cemented silica m sorting and ash s in sample KgL2 atrix and the micr aggregations. Poly -1 are composed o o glass fragments. modality and uni f ash shards (B) a modality are thus nd ash shards agg 119 not diagnostic regates (C, D). 120 Table 6-4 General characteristics of primary and secondary ash units. The presence of a combination of these features usually distinguishes primary from secondary ash in terrestrial distal deposits where the tephra appear in metre-thick outcrops. The problems occur when the ash is found in sub-millimetre-scale strata, i.e. in cryptotephra or microtephra. PRIMARY ASH SECONDARY ASH Thickness Cm-scale (usually 4-10 cm) Can reach 10+ m Colour White looking (10 YR 8/1 and 8/2; 7.5 YR 8/2) Wide range of grey-toned colours (10 YR 4/2; 10 YR 8/3, 7/3 and 7/4) Basal contact Sharp non-erosive Gradual, erosive, non-erosive Upper contact Sharp non-erosive if sealed by non- volcanic sediments; gradual if overloaded by reworked units/ bioturbated Gradual, erosive, non-erosive Sedimentary structures Variable, but usually no trace of vertical grading or water percolation structure; ball and pillows structures can be found at the upper boundary, if the ash was deposited in an aqueous environment Variable: massive, horizontal stratification, ripple-cross lamination, parallel thin lamination, cross- bedded. Grain shape No difference No difference Grain-size distributions Unimodal Unimodal; polymodal Lateral persistency Variable Consistent and variable Cementation Variable Variable 6.5.1.1 The Kota Tampan YTT layer and archaeological implications Collings (1938, p. 575) described the ash at Kota Tampan as a “deposit of volcanic tuff overlying a bed of sand and gravel, which itself rests on laterite, [..] probably an old terrace of the Perak River”. The ash was reported to be 3 m in thickness, overlying gravel beds from which Palaeolithic implements belonging to 'Tampanian' industry had been recovered (Collings, 1938). Although the ash was not then characterised as primary or secondary, this author's stratigraphic description appears comparable with that at KgL3. He obtained a date of ~ 35 ka for the Tampan Palaeolithic tools, based on 14C dating of wood obtained immediately underlying the ash (Stauffer, 1973). Later the dating of the YTT ash to 75 ka led to a corresponding increase in the age of the Tampanian tools (Ninkovich 1978a). However, comparison with the sequences examined here indicates that the excessive thickness of the Kota Tampan ash provides a strong suggestion of the secondary nature of the deposit. Since there is no record of a basal primary ash unit at this site, the implication is that the Kota Tampan ash could be reworked and deposited at a later date. 121 6.5.2 Mechanisms of tephra reworking in the Lenggong valley The reported sedimentary structures and the particle-size distributions consistently suggest fluvial transport as the main process of accumulation and deposition of the distal tephra in the Lenggong valley. The absence of grading argues against tephra fallout as the predominant depositional process (Favalli et al., 2006). All the sequences studied are poorly to very poorly sorted, classified texturally as muddy sand, and sedimentologically classified as coarse silt, very coarse silt or very fine sand (Table 6-2). The deposits of KgL1, KgL2 and BTS are massive, while KgL3 showed horizontal laminations and planar bedding. Modern plant material has been found in all the deposits, particularly in KgL2. The percentage of ash varies in each deposit, although the principal grain-size interval (63-125 μm) contains 71 - 99% ash. The tephra at KgL3, situated near the main channel, includes marked horizontal laminae and an oxidised ash lens ~ 10 cm thick, sandwiched between two ~ 5 cm thick clay hardpans. The lens is capped by 2.30 m of reworked tephra, sub-horizontally parallel laminated. The basal contact with the non-volcanic unit is non-erosional. The upper deposits at KgL3 are the product of the transport and redeposition of ash remobilised from upstream, probably by a flood flow. Yet, the wavy, laminated clay hardpans indicate deposition from suspension in slack water. Subaerial exposure preceded another phase of flooding and inundation. These characteristics suggest that KgL3 was deposited in a vegetated floodplain or swamp, characterised by seasonal flooding and desiccation (Nakayama and Yoshikawa, 1997). Similar tephra deposits separated by clay hardpans have been identified at Jwalapuram, in India (Petraglia et al., 2007). The deposit shows six clay hardpans through the ash sequence. Petraglia et al. (2007) interpreted the couplets as representing six monsoon cycles, characterised by wet (ash) and dry (clay) periods. KgL3 includes two clay hardpans, suggesting that the lens might represent one rainy season embedded between two dry seasons. The ash at KgL1 and 2 was deposited in a depression. The particle-size distributions and mineralogical associations indicate a chaotic mixture of silty-sized ash and fine-sand-sized ash (Figure 6-7). This suggests that the two sequences are likely to be derived from slumping sedimentation in a colluvial area (Kataoka, 2005) possibly during a major flood event that remobilised the fall deposits from the surrounding hills. Such volcaniclastic facies might represent 122 a direct effect of the low liquefaction resistance of volcaniclastic deposits (Nakayama, 2001). Such types of slump deposits have been identified in volcaniclastic sequences in the Pliocene Mushono tephra, in central Japan (Kataoka, 2005). Notably, although KgL1 and 2 are likely to have been deposited during the same slumping event, they show contrasting sedimentological characteristics. The high mica content at KgL2. (Figure 6-8) could have arisen from site-specific syn- or post-depositional processes. The bedrock underlying the catchment is micaceous granite. The presence of a nearby tributary could therefore have brought allochthonous mica from its local catchment. Alternatively, the KgL2 ash might originally have been closer to the palaeochannel bank, where it could have been more exposed to local bedrock weathering. At this site the lower units appear to be enriched in mica, probably eroded from underlying granites during flood events. Conversely, the mica could also be a primary magmatic component of the YTT tephra, since biotite is a primary product of the YTT bulk material (Chesner, 1998; Smith et al., 2011), and the accumulation of mica flakes in the basal stratum could be related to the density differences between mica (ρ=2900 kg/m3) and rhyolite glass shards (ρ=2350-2450 kg/m3). However, mica flakes may behave very differently from glass shards hydrodynamically, and the shape of the grains could be more important than density. This suggests that several site-specific parameters determined the final characteristics of the preserved deposits. BTS is massive in aspect, similar to KgL2 1 and 2. However, the textural analyses showed that BTS is consistently finer (2% clay) and presents clear alternating subunits of clay-like and silty ash (Figure 6-5, Figure 6-7). Magnetic susceptibility reveals clear differences between lower and upper silt (Figure 6-7d). Massive resedimented units indicate that reworking occurred through hyperconcentrated flows resulting in sudden aggradation of ash (Segschneider et al., 2002; Kataoka, 2003; Manville et al., 2005; Manville et al., 2009a; Manville et al., 2009b). This suggests that BTS is the result of a mudflow (Nakayama and Yoshikawa, 1997) and the changes in particle size between bottom and top could indicate waxing and waning flow. Examples of similar lahar facies have been reported of the Ebisutoge–Fukuda tephra (Kataoka et al., 2009), and Ohta tephra of the Tokai Group (Nakayama and Yoshikawa, 1997), both in central Japan. 123 6.5.2.1 Time of deposition and implications for the YTT environmental impact debate Magnetic susceptibility of sediments is an indicator of soil-forming processes in areas containing uniform parent material (Mullins, 1977). The constant values recorded for the samples analysed suggest the tephra accumulated in a short period. Neither the sedimentation rate, nor the total accumulation time for each deposit can be determined in the absence of bracketing ages below and above the units, and such data are not yet available for the Lenggong deposits (neither volcanic nor siliciclastic). Nevertheless, the facies suggest mudflow, slumping and flood flow as the main depositional processes, mechanisms that usually operate on timescales of hours or days (Nammah et al., 1986; Hayes et al., 2002; Mastrolorenzo et al., 2002). The only site that suggests subaerial exposure and a clear depositional hiatus is KgL3. Here a lens of ~ 10 cm of ash was deposited, probably from material in suspension, and sealed between two clay hardpans (Figure 6-6). This site is thus the best candidate for possible palaeoenvironmental studies in the area. Nevertheless, attention is required when interpreting the palaeoenvironmental signals extracted from reworked tephra. Firstly, the time lag between the primary deposition of the YTT and the flood events is unknown. Therefore, the genesis of the palaeorecords might not be directly related to the eruption impact. Moreover, the records are likely to be influenced by site-specific morphological characteristics. This has been recently considered by Blinkhorn et al. (2012). These authors demonstrated that the oxygen and carbon stable isotope traces extracted from pedogenic carbonate beneath and overlying the YTT in twelve terrestrial deposits at Jwalapuram (see §2.1 and Figure 2-1) were extremely variable. Such variability appeared directly linked to site-specific features (i.e. topographic height), rather than post-eruptive environmental feedbacks. This recent discovery reinforces the findings of this thesis, demonstrating the strong controls of the receiving environments on the tephra taphonomy. These have profound implications for the wider YTT debate, where conclusions regarding a drastic impact of the ashfall have been reached upon palaeoenvironmental reconstructions from proxies extracted from reworked tephra sequences (e.g. Williams et al., 2009; Haslam et al., 2010). In the light of the process highlighted herein, such conclusions maybe unsafe. In a broader sense the processes identified indicate that environmental techniques must be adapted to reflect the sedimentological and stratigraphical characteristics of the tephra sediments at any particular site. 124 6.6 Conclusion Analysis of the stratigraphy and sedimentology of four new YTT localities in the Lenggong valley, Malaysia, have demonstrated that these tephra sequences are associated with fluvial and colluvial transport and deposition. Three volcaniclastic facies have been identified corresponding to flood- flow, mudflow and slumping sedimentation. Both major elements and REE chemical fingerprints confirm that the tephra in these facies corresponds to the YTT eruption The field stratigraphy, particle mineralogical associations and size distribution of the sediments together indicate that the tephra deposits are reworked. The data suggest that the ash deposition occurred rapidly, on the scale of days or months. Although there are no dates currently available for the Lenggong sediments, further studies should be undertaken in order to assess the absolute age of the floods events and their accumulation rate. KgL3 is the only site at which non-volcanic material is exposed beneath the ash and where the mechanism of deposition allowed the development of an undisturbed ash unit. It should therefore be a good candidate for further studies to establish the detailed depositional chronology. The investigations reported here suggest that other areas of Peninsular Malaysia are likely to host YTT deposits. These include the Singar sub-catchment or the Temengor Lake, which might provide a locus for the testing of the mechanisms of accumulation and preservation outlined here. Analyses of the mechanism of tephra reworking are particularly important in the case of the YTT, given the wide use of the ash deposits to assess the YTT environmental impact and its possible consequences for human populations. The results highlight the need to address new questions in order to refine the YTT debate, for example: how the rate of accumulation of the reworked ash sequence can be determined. Are there palaeoenvironmental proxies that can be extrapolated from the reworked sequence and with certainty related to the ashfall impact? On a global scale, the work reported herein demonstrates the importance of producing detailed examinations of tephra units and their sedimentary environments, particularly when the tephra are used for chronological correlation, and where the occurrence of the ashfall could have had strong environmental impacts. This is particularly important in situations where substantial sediment transport and topographic contrasts predominate, as in Malaysia. 125 A major problem in the application of tephra for chronology and stratigraphy is the differentiation between primary and secondary ash. This chapter has demonstrated that particle- size analyses alone cannot be used in isolation to distinguish the two. This has significant implications when correlation is based on micro-tephra or cryptotephra. A new method is therefore required to differentiate unequivocally between primary and secondary ash facies. Ideally this should be a micro-scale technique that allows us reliably to distinguish the two on the basis of the characteristic features of single grains. These concluding remarks bring the thesis to the point where it is appropriate to reflect on what has been achieved, and what still remains to be done in the future. Chapter seven will therefore discuss the conclusions of this work and the future objectives that flow from the point that this research has reached. 127 Chapter 7. Conclusions Albert Einstein, in his Ideas and Opinions, suggested that “A great effort in the enterprise of science goes into constructing ‘well-posed problems’, that is, to directing and focusing the spotlight of enquiry to those questions that have certain and unambiguous answers” (Einstein, 1954, p. vii). This study does not provide a final answer to the question ‘What was the environmental impact of the YTT?’. However, it has clearly demonstrated that the methods previously used to obtain such answers have neglected vital aspects of the YTT characteristics. For instance, previous estimates of the erupted volume of ash have been based on a method that has been here demonstrated to be insufficient to modelling the co-ignimbrite ashfall dispersal. The volume estimates of Rose and Chesner (1987) and that of Matthews et al.(2012) should therefore be considered only as crude approximations and be used cautiously in any further modelling of the eruption. This thesis has also demonstrated two important tephrostratigraphic principles ignored in the previous literature. Firstly, if ash has been reworked, it should not be used as chronostratigraphic marker. It seems a basic observation, yet the majority of palaeoenvironmental reconstructions at terrestrial sites have been based on unverified sites, where the ash was clearly reworked, or at best of dubious status (i.e. Williams et al., 2009). Secondly, it shows that the reworking of ash has dramatic consequences on its distribution and taphonomic characteristics, which, in consequence, cannot be related only to the volcanic signal; put simply, a clear understanding of reworking processes is essential. For example, palaeoenvironmental signals extracted from carbonate nodules in the tephra sequences of Jwalapuram (Haslam et al., 2010; Blinkhorn et al., 2012) are of limited application in the absence of an account of the reworking processes that generated the deposits from which the proxies were extracted. Similarly, the standard reconstruction methods such as those used by Jones ([2010], changes in sedimentation patterns, particle size distributions) can be strongly influenced by local transport mechanisms, and it is not clear if they can record the volcanic impact at all. 128 This work h to redefine Here, theref limitations broader imp 7.1 Synth Figure 7- main issu data and (discusse The princip reached by preserved a particle size of fine and as provided the problem ore, the con of the studi lications (7 esis 1 Conceptual es. Light blue the incompa d in § 7.3). al differenc the ashfall sh deposits. s of known very fine pa a contribu and cons cluding ch es (7.2) pro .4). diagram of t represents b tibility of the e between th (more than Chapter th YTT sites. rticles, and tion to the truct well-f apter synthe poses new he organizati road issues re literature rep e YTT and 4000 km f ree introdu The data rev that neither YTT literatu ocused and sises the m directions fo on of the key lated to the Y orts. The re any other k rom the so ced a meta ealed that the particle re, and mo useful que ain points o r future wo chapters of TT literature d boxes repre nown erup urce) and t -analysis of the YTT de -sizes nor t re significan stions for f the thesis rk (7.3), an this thesis, hi , i.e. the lack sent future r tion is the e he exceptio the primar posits are la he thicknes tly, it allow future resea (7.1), ident d discusses ghlighting th of substantia esearch topic xtreme dist nal thicknes y thickness rgely comp s of the dep s us rch. ifies the e l s ance s of and osed osits 129 decrease in relation to the distance from the vent. It is also noted that reported data were often incomplete and inconsistent, which limited the scope of broader analysis. Arguably the most widely described characteristics of the YTT that have been reported are the geochemical fingerprints of the tephra in each location. Chapter four compiled these data and tested the robustness and comparability of analyses from different authors, discovering inter- laboratory biases. Importantly, it showed that comparison of immobile elements provides evidence of significant chemical variation. This novel analysis showed how the YTT ash carries the stamp of compositional zonation established in the magma reservoir at the time of the eruption. The chapter also attempted to resolve the issue of the ash of Morgaon, India, dated as OTT but geochemically similar to the YTT. Analyses of the ratios of major elements were unable to resolve the issue, demonstrating that the OTT and YTT major elements are fundamentally identical. Chapter five presented the case of another important Indian YTT layer, moving from analysis of the YTT at the scale of individual particles to the YTT as thick tephra deposits. The fundamental issue of differentiation between primary and secondary ash was addressed by developing the tephrostratigraphy of the Son Valley. This also demonstrated the necessity of discriminating between tephra transport mechanisms (in this case, fluvial). Finally Chapter six used the tephra deposits, in this case the secondary ash deposits in the Lenggong valley, Malaysia, to reveal tephra reworking mechanisms. The study showed that the accumulation of tephra occurred reasonably rapidly, probably on the timescale of decades, strongly influenced by proximity to flowing water and local landscape features. A detailed analysis of particle size distributions and allochthonous components showed that these characteristics are not diagnostic of the source of the ash. This chapter further highlighted the need for future work to assess the relative rate and timescale of tephra accumulation. 130 7.2 Limitations of the research In addition to the substantial progress outlined above, the research has clearly demonstrated the limitations of current geochemical and sedimentological methods. It highlights three important questions that remain unresolved. Can we reliably distinguish primary and secondary ash? A key challenge is to develop a quantitative method to distinguish primary and secondary ash in the lab. Current practice is to use a suite of characteristics – such as colour, particle size, presence of allochthonous components, thickness and nature of the contact boundaries – to distinguish the two, but the approach is fundamentally qualitative. These analyses, the most detailed to date, were unable to identify characteristics that reliably distinguish the source of the ash. Estimating primary tephra thickness is also subjective, since the upper boundary between primary and the secondary ash is often poorly defined. Can we estimate the rate of accumulation of reworked tephra? Poor temporal resolution of the tephra sequence leaves substantial uncertainty in estimating the timeframe of secondary ash deposition. This is crucial in considering the potential environmental impact of the ashfall, since the time taken for the system to re-establish its pre-eruption equilibrium is an important indicator of damage to the receiving environment. Can we determine the difference between OTT and YTT tephra? Current methods are unable to distinguish between OTT and YTT composition, and recent findings of OTT products some 1000 km from the eruption site now suggest that OTT could have been of similar magnitude to the YTT. The Morgaon ash has now been dated to ~ 800 ka, raising the question whether OTT deposits are present in India. This brings new importance to this geochemical issue, as it has implications for our understanding of early human migration patterns. 7.3 Future research The progress towards improved tephrostratigraphy presented in this thesis can be used as a springboard for future research to address the unresolved questions presented above. These might include: 131 Assessment of quantitative differences between primary and secondary ash by establishing diagenetic features on the surfaces of individual grains. Weathering of volcanic ash begins immediately after sedimentation; the extent of alteration depends on specific conditions including exposure to meteoric water and the depth of burial. Although I have demonstrated that rhyolitic ash is resistant to alteration (Chapter four), high-resolution IR-spectra on rhyolitic glasses from Kamchatka, Russia, showed a modest development of opal during different lithogenic stages (Kuznetsova et al., 2009). The presence of such secondary products could be used as a diagnostic indicator of primary vs. secondary ash. However, clay mineral analyses previously performed on YTT ash (the author, unpublished data) showed that clay minerals are difficult to detect when associated with a large amount of ash. Crystal fractions < 1 μm, must be used and special care is needed when detecting the opal by x-ray diffraction, since even a small quantity of glass shards can deflect the x-rays. Use of fallout and/or lithogenic radionuclides to assess ash sedimentation rates. Medium-term (101–102 years) rates of overbank sedimentation on river floodplains have been successfully measured using the fallout radionuclides 137Cs and excess 210Pb. The YTT is too old for the use of these indicators, but the ratio between radionuclides 26Al and 10Be (half-life of 7.30 × 105 and 1.5 × 106 years respectively (Balco et al., 2005)) might be used instead. The Al/Be ratio varies with the duration of burial and these elements are incorporated in quartz grains accumulated with the tephra. Thus the ratio might indicate the time between burial of the primary ash and the accumulation of secondary ash (Pelletier et al., 2008). Alternative geochemical techniques to distinguish between OTT and YTT. Analysis of welded tuffs belonging to the OTT in Sumatra suggested that the rare elements Ba, Sr and Rb might discriminate between OTT and YTT (Chesner, 1998). Until the discovery of OTT tephra in the South China Sea, it was assumed to be a minor eruption, and thus OTT distal ash has been characterised only in terms of major components, and rare elements analyses are not presently available. The first step therefore would be to analyse the rare element composition of known OTT samples, such as the OTT recovered from site 578 or 1143A of the Ocean Drilling Programme, two marine cores that reported all three of the Toba ash layers. If these rare elements cannot be used to distinguish between the two, another approach might be to analyse the light 132 rare earth element (LREE) composition of accessory minerals present in the tephra such as apatite or allanite. Allanite in particular is LREE-rich, and previous analyses showed that the YTT allanite is higher in such elements than is the OTT allanite (Chesner and Ettlinger, 1989; Chesner, 1998). These accessory minerals are however infrequently found in distal tephra deposits. 7.4 Broader implications This work has demonstrated several stratigraphic misconceptions and identified new approaches to enhance volcanological understanding. It has also highlighted several remaining issues in YTT research, and important ways in which to address them. This research has focused on the YTT eruption, an exceptional event in the Earth’s recent history, but it has broader implications. Volcanology. The problem of complex settling behaviours of small particles has important implications for recent ash cloud monitoring for aviation hazards, as seen after the 2010 eruptions of Eyjafjallajökull. Jet engines can be severely damaged by volcanic ash and it is therefore important to understand the complex dynamics between the volcanic cloud, particle behaviour and atmospheric transport. Similarly, the phenomenon of ash aggregation seen in the survey sites in Malaysia has recently been discovered in some ashfall deposits from the 1981 eruption of Mount St. Helens (Durant et al., 2009). It is now believed that ash aggregates play an important role in controlling ash dispersal and sedimentation, although the processes by which they form remain uncertain. Climatology. Distinguishing primary from secondary ash is especially important in the case of cryptotephra or in cases where the geological section does not allow separation of the two. This might prove extremely useful in climatic reconstructions. For example, cryptotephra recovered from marine and lacustrine cores in Scotland and the North Sea, if correctly dated, could significantly improve the chronology of Holocene climatic oscillations, with implications for the role of climatic changes in shaping the development of European communities. Geochemistry. Chapter 4 has shown how rhyolitic ash releases elements into the receiving environment. Many of the elements which can leach from the ash (Al, Fe, Na, K) are included in drinking water guidelines due to their toxicity, and may constitute potential hazards to the 133 environment and human health. The environmental geochemistry of ancient volcanic ash could therefore help us to evaluate water supply systems affected by ash leaching after, for example, a strong rain event (cf. Crowley et al., 1994). Geoarchaeology. The YTT is an important marker in Archaeological studies, partly because the eruption coincided approximately with the spread of modern humans out of Africa and across Asia (James and Petraglia, 2005; Petraglia et al., 2009; Armitage et al., 2011). When stone tools of the “Tampanian Men” were found in Kota Tampan, Malaysia, at the beginning of the 1960s, the sediments associated with these archaeological artefacts were radiocarbon dated at ~ 35 ka BP. Once it was discovered that the ash above those sediments was YTT, the age of the stone tools was revised to ~ 74 ka. If the Kota Tampan ash proves to be the product of reworking, it could cast doubt on the older age attributed to the artefacts. This has major implications not only for Malaysian archaeology, but also for studies tracing the migration of modern humans from Malaysia to Australasia. Revising our understanding of the YTT marker, and the broader implications this might have for those archaeological theories which rely upon it, suggests creating a new mindset within the discipline of Geoarchaeology. Multidisciplinary Sciences. Michael Petraglia, in the Quaternary International special volume “The Toba Volcanic Super-eruption of 74,000 Years Ago: Climate Change, Environments, and Evolving Humans”, concluded the introductory preface by saying “This work indicates the need for substantial further research on the Toba super-eruption and its impact. Clearly, the most profitable way forward is to form interdisciplinary collaborations among volcanologists, climate modellers, plant scientists, mammalian palaeontologists, geneticists, palaeoanthropologists, and archaeologists.” (Petraglia et al., 2012, p.3). 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Raw geochemical data 9.1 Internal Standards (in wt%) measured with LA-ICP-MS Element Chondrite NIST 610 NIST 612 NIST614 KL2-G ref T1-G ref BIR-1 lit BHVO-2 lit BCR-2 lit 9Be 0,04 465,6 37,74 1,12 0,9 2 0,58 0,9 1,75 24Mg 143000 465,3 77,44 39,9666666 7 43800 22600 58493 43598 21648 27Al 12900 10005,57 11164,6 10983,2733 3 69300 90000 82033,9639 7 71448,9363 6 71448,9363 6 30Si 160000 328329,15 335916,8 0 234000 273000 224179 233247 252879 43Ca 13500 81833,26 85262,5 81833 77200 50600 95056 81476 50887 45Sc 8,64 441,1 41,05 2,03 32,3 26,7 44 32 33 51V 85 441,7 39,22 1,03 370 190 313 317 416 60Ni 16500 443,9 38,44 2 116 13 166 119 17,7 85Rb 3,45 431,1 31,63 0,82 8,9 80 0,24 9,08 46,9 88Sr 11,9 497,4 76,15 45,7 364 283 110 396 340 89Y 2,25 449,9 38,25 0,83 26,8 23,2 17 26 37 90Zr 5,54 439,9 35,99 0,95 159 147 14,5 172 188 93Nb 0,375 419,4 38,06 0,89 15,8 9,1 0,55 18 11 137Ba 3,41 424,1 37,74 3,09 123 382 6,4 131 677 139La 0,367 457,4 35,77 0,71 13,2 69 0,58 15,2 24,9 140Ce 0,957 447,8 38,35 0,79 32,9 127 1,85 37,5 52,9 141Pr 0,137 429,8 37,16 0,78 4,71 12,1 0,37 5,29 6,57 143Nd 0,711 430,8 35,24 0,76 21,7 40,7 2,35 24,5 28,7 147Sm 0,231 450,5 36,72 0,73 5,55 6,52 1,1 6,07 6,57 153Eu 0,087 461,1 34,44 0,77 1,95 1,21 0,52 2,07 1,96 157Gd 0,306 419,9 36,95 0,72 6,1 5,2 1,97 6,24 6,75 159Tb 0,058 442,8 35,92 0,68 0,93 0,82 0,38 0,936 1,07 163Dy 0,381 426,5 35,97 0,77 5,35 4,44 2,5 5,31 6,41 165Ho 0,0851 449,4 37,87 0,79 0,99 0,83 0,57 0,972 1,3 166Er 0,249 426 37,43 0,8 2,64 2,42 1,63 2,54 3,66 169Tm 0,0356 420,1 37,55 0,68 0,336 0,35 0,25 0,33 0,54 172Yb 0,248 461,5 39,95 0,76 2 2,32 1,6 2 3,38 175Lu 0,0381 434,7 37,71 0,77 0,296 0,35 0,25 0,274 0,51 156 178Hf 0,179 417,7 34,77 0,75 4,14 3,9 0,56 4,1 4,8 181Ta 0,026 376,6 39,77 0,86 0,97 0,45 0,06 1,4 0,82 208Pb 3,65 413,3 38,96 3,74 2,2 13 3 1,6 11 232Th 0,0425 450,6 37,23 0,81 1,03 30 0,03 1,2 6,2 238U 0,0122 457,1 37,15 0,86 0,55 1,67 0,01 0,39 1,69 157 9.2 Rare elements geochemical analyses (LA-ICP-MS) GLITTER4.0: Laser Ablation Analysis Results NB: Please note that all values for the internal standard(s) are reported in units of weight% oxide, all other values reported in ppm GLITTER!: Trace Element Concentrations MDL filtered. Element Chondrite MRB-3_1 MRB-3_2 MRB-3_3 MRB-3_4 MRB-3_5 MRB-3_6 MRB-3_7 MRB-3_8 9Be 0,04 1,89 <2.18 6,26 2,71 1,1 2,72 <3.16 6,17 24Mg 143000 0,066 0,066 0,066 0,066 0,066 0,066 0,066 0,066 27Al 12900 78277,82 67905,57 103804,54 77833,88 30091,95 54824,66 82008,87 90319,96 30Si 160000 294102,41 270534,88 526444,88 331753,66 122790,2 275113,59 339311,13 401194,78 43Ca 13500 4948,01 4402,13 6736,02 5738,65 1450,42 3999,33 4361,55 4207,24 45Sc 8,64 5,11 3,74 7,76 4,58 2,01 2,89 3,57 7,71 51V 85 1,51 3,67 0,9 7,21 5,52 6,41 1,87 3,4 60Ni 16500 0,55 2,67 <0.39 <1.26 1,91 <0.50 0,75 1,52 85Rb 3,45 302,49 213,82 494,13 267,52 89,87 173,41 268,55 397,49 88Sr 11,9 16,34 32,62 19,15 33,82 17,96 39,4 32,73 21,45 89Y 2,25 32,78 20,17 42,59 26,33 8,41 14,17 27 41,56 90Zr 5,54 73,69 54,55 83,91 51,89 26,29 38,79 66,43 72,1 93Nb 0,375 15,29 9,87 24,54 12,3 4,5 8,63 13,68 18,58 137Ba 3,41 55,16 302,77 74,63 247,14 203,73 400,14 235,93 77,75 139La 0,367 18,39 20,79 24,61 20,68 10,1 18,7 21,89 23,65 140Ce 0,957 39,66 39,59 64,48 43,31 19,83 39,67 45,45 50,65 141Pr 0,137 4,21 3,89 6,29 4,62 1,79 3,54 4,38 5,03 143Nd 0,711 15,03 12,22 21,17 15,66 7,13 13,4 15,8 21,47 147Sm 0,231 3,56 2,97 5,58 3 1,27 2,66 3,9 4,29 153Eu 0,087 0,2 0,216 0,259 0,319 0,119 0,251 0,304 0,249 157Gd 0,306 4,07 2,47 5,08 2,93 0,95 1,63 3,19 4,84 159Tb 0,058 0,656 0,438 0,989 0,642 0,125 0,353 0,738 0,93 163Dy 0,381 4,47 2,8 7,02 4,24 1,22 2,22 4,11 6,53 165Ho 0,0851 1,02 0,656 1,31 0,851 0,293 0,512 1,06 1,51 166Er 0,249 2,6 2,05 4,34 2,52 0,808 1,32 2,92 3,56 169Tm 0,0356 0,448 0,333 0,762 0,473 0,137 0,284 0,531 0,574 172Yb 0,248 4,07 3,5 5,45 3,48 1,02 1,7 3,86 5,55 175Lu 0,0381 0,622 0,524 0,844 0,544 0,167 0,311 0,571 0,86 178Hf 0,179 2,63 2,29 3,44 2,74 1,05 1,76 2,9 3,3 181Ta 0,026 1,55 0,98 2,65 1,37 0,457 0,801 1,47 2,08 208Pb 3,65 43,77 33,81 64,14 40,16 20,3 30,07 43,98 56,32 232Th 0,0425 27,63 18,53 41,01 25,92 8,8 15,79 27,86 37,41 238U 0,0122 6,98 3,94 11,64 5,63 1,68 3,15 5,62 9,16 REE Chondrite normalised MRB-3_1 MRB-3_2 MRB-3_3 MRB-3_4 MRB-3_5 MRB-3_6 MRB-3_7 MRB-3_8 La 0,367 50,1090 56,6485 67,0572 56,3488 27,5204 50,9537 59,6458 64,4414 Ce 0,957 41,4420 41,3689 67,3772 45,2560 20,7210 41,4525 47,4922 52,9258 Pr 0,137 30,7299 28,3942 45,9124 33,7226 13,0657 25,8394 31,9708 36,7153 Nd 0,711 21,1392 17,1871 29,7750 22,0253 10,0281 18,8467 22,2222 30,1969 Sm 0,231 15,4113 12,8571 24,1558 12,9870 5,4978 11,5152 16,8831 18,5714 Eu 0,087 2,2989 2,4828 2,9770 3,6667 1,3678 2,8851 3,4943 2,8621 Gd 0,306 13,3007 8,0719 16,6013 9,5752 3,1046 5,3268 10,4248 15,8170 Tb 0,058 11,3103 7,5517 17,0517 11,0690 2,1552 6,0862 12,7241 16,0345 Dy 0,381 11,7323 7,3491 18,4252 11,1286 3,2021 5,8268 10,7874 17,1391 Ho 0,0851 11,9859 7,7086 15,3937 10,0000 3,4430 6,0165 12,4559 17,7438 Er 0,249 10,4418 8,2329 17,4297 10,1205 3,2450 5,3012 11,7269 14,2972 Tm 0,0356 12,5843 9,3539 21,4045 13,2865 3,8483 7,9775 14,9157 16,1236 Yb 0,248 16,4113 14,1129 21,9758 14,0323 4,1129 6,8548 15,5645 22,3790 Lu 0,0381 16,3255 13,7533 22,1522 14,2782 4,3832 8,1627 14,9869 22,5722 158 Element Chondrite MRB-3_9 MRB-3_10 9Be 0,04 13,09 5,09 24Mg 143000 0,066 0,066 27Al 12900 91886,53 78035,2 30Si 160000 386432,56 345499,63 43Ca 13500 <3955.07 4328,99 45Sc 8,64 6,88 4,45 51V 85 6,91 1,7 60Ni 16500 2,67 0,77 85Rb 3,45 419,33 290,1 88Sr 11,9 17,9 34,95 89Y 2,25 60,81 27,52 90Zr 5,54 113,21 67,96 93Nb 0,375 23,52 14,2 137Ba 3,41 75,88 237,64 139La 0,367 26,8 22,2 140Ce 0,957 63,02 51,45 141Pr 0,137 6,46 4,64 143Nd 0,711 31,2 16,58 147Sm 0,231 4,66 3,49 153Eu 0,087 <0.00 0,351 157Gd 0,306 4,25 3,16 159Tb 0,058 1,44 0,743 163Dy 0,381 6,72 4,14 165Ho 0,0851 2,03 1,03 166Er 0,249 5,16 2,99 169Tm 0,0356 0,88 0,453 172Yb 0,248 7,48 3,64 175Lu 0,0381 1,25 0,529 178Hf 0,179 4,68 2,74 181Ta 0,026 2,47 1,52 208Pb 3,65 50,53 43,23 232Th 0,0425 43,35 26,91 238U 0,0122 9,23 6,34 REE Chondrite normalised MRB-3_9 MRB-3_10 La 0,367 73,0245 60,4905 Ce 0,957 65,8516 53,7618 Pr 0,137 47,1533 33,8686 Nd 0,711 43,8819 23,3193 Sm 0,231 20,1732 15,1082 Eu 0,087 0.00 4,0345 Gd 0,306 13,8889 10,3268 Tb 0,058 24,8276 12,8103 Dy 0,381 17,6378 10,8661 Ho 0,0851 23,8543 12,1034 Er 0,249 20,7229 12,0080 Tm 0,0356 24,7191 12,7247 Yb 0,248 30,1613 14,6774 Lu 0,0381 32,8084 13,8845 159 Element Chondrite BR-6_1 BR-6_2 BR-6_3 BR-6_4 BR-6_5 BR-6_6 BR-6_7 BR-6_8 9Be 0,04 1,06 <0.00 <0.00 <0.67 1,93 1,45 4,11 <0.00 24Mg 143000 0,061 0,061 0,061 0,061 0,061 0,061 0,061 0,061 27Al 12900 34499,13 7365,98 12886,47 10663,25 20495,98 69590,71 59175,27 24171,42 30Si 160000 145561,72 32782,83 63756,77 48506,52 94165,23 316853,63 299527,38 148638,83 43Ca 13500 1944,56 325,36 1059,11 426,97 1205,9 3716,32 3425,15 1641,99 45Sc 8,64 1,96 0,73 0,94 0,79 1,51 5,52 3,78 2,84 51V 85 2,13 1,3 3,24 2,88 2,31 1,27 1,44 4,97 60Ni 16500 1,52 0,55 2,29 1,89 1,73 1 0,41 <1.11 85Rb 3,45 104,94 33,79 45,77 40,4 70,79 312,48 276,39 87,69 88Sr 11,9 23,73 3,89 6,27 1,71 8,86 12,12 13,92 15,53 89Y 2,25 9,57 2,02 3,81 4,2 5,85 34,26 27,46 7,63 90Zr 5,54 31,23 7,68 13,78 11,53 19,73 46,75 49,06 27,25 93Nb 0,375 5,4 1,95 2,27 2,31 3,84 15,12 13,96 4,13 137Ba 3,41 264,54 41,17 48,97 9,04 90,47 38,27 43,79 139,34 139La 0,367 12,23 2,31 3,59 2,34 5,45 19,16 16,09 8,24 140Ce 0,957 24,55 4,92 7,64 5,34 12,12 56,95 36,91 16,51 141Pr 0,137 2,26 0,441 0,733 0,568 1,09 4,28 3,67 1,64 143Nd 0,711 7,77 1,51 2,63 1,92 3,37 15,83 13,56 5,25 147Sm 0,231 1,79 0,201 0,443 0,581 0,69 3,61 3,19 0,99 153Eu 0,087 0,139 0,042 0,036 0,0215 0,058 0,131 0,116 0,145 157Gd 0,306 1,21 0,186 0,464 0,478 0,73 3,54 3,57 1,09 159Tb 0,058 0,214 0,0443 0,102 0,085 0,165 0,82 0,635 0,165 163Dy 0,381 1,33 0,281 0,553 0,578 0,85 5,41 3,6 0,69 165Ho 0,0851 0,335 0,072 0,128 0,148 0,174 1,04 0,823 0,243 166Er 0,249 1,14 0,194 0,354 0,397 0,79 3,14 2,77 0,75 169Tm 0,0356 0,168 0,0395 0,0619 0,0642 0,125 0,548 0,494 0,108 172Yb 0,248 1,32 0,297 0,574 0,532 0,8 4,45 3,51 0,98 175Lu 0,0381 0,197 0,0537 0,092 0,075 0,138 0,651 0,536 0,156 178Hf 0,179 1,13 0,231 0,475 0,497 0,92 2,44 2,14 0,93 181Ta 0,026 0,536 0,125 0,224 0,217 0,363 1,69 1,51 0,522 208Pb 3,65 16,34 3,89 7,75 8,15 10,8 40,51 38,31 14,13 232Th 0,0425 9,69 2,08 4,02 3,89 6,6 31,51 26,36 8,81 238U 0,0122 2,01 0,466 0,934 0,958 1,42 7,38 6,99 1,91 REE Chondrite normalised BR-6_1 BR-6_2 BR-6_3 BR-6_4 BR-6_5 BR-6_6 BR-6_7 BR-6_8 La 0,367 33,3243 6,2943 9,7820 6,3760 14,8501 52,2071 43,8420 22,4523 Ce 0,957 25,6531 5,1411 7,9833 5,5799 12,6646 59,5089 38,5684 17,2518 Pr 0,137 16,4964 3,2190 5,3504 4,1460 7,9562 31,2409 26,7883 11,9708 Nd 0,711 10,9283 2,1238 3,6990 2,7004 4,7398 22,2644 19,0717 7,3840 Sm 0,231 7,7489 0,8701 1,9177 2,5152 2,9870 15,6277 13,8095 4,2857 Eu 0,087 1,5977 0,4828 0,4138 0,2471 0,6667 1,5057 1,3333 1,6667 Gd 0,306 3,9542 0,6078 1,5163 1,5621 2,3856 11,5686 11,6667 3,5621 Tb 0,058 3,6897 0,7638 1,7586 1,4655 2,8448 14,1379 10,9483 2,8448 Dy 0,381 3,4908 0,7375 1,4514 1,5171 2,2310 14,1995 9,4488 1,8110 Ho 0,0851 3,9365 0,8461 1,5041 1,7391 2,0447 12,2209 9,6710 2,8555 Er 0,249 4,5783 0,7791 1,4217 1,5944 3,1727 12,6104 11,1245 3,0120 Tm 0,0356 4,7191 1,1096 1,7388 1,8034 3,5112 15,3933 13,8764 3,0337 Yb 0,248 5,3226 1,1976 2,3145 2,1452 3,2258 17,9435 14,1532 3,9516 Lu 0,0381 5,1706 1,4094 2,4147 1,9685 3,6220 17,0866 14,0682 4,0945 160 Element Chondrite BR-6_9 9Be 0,04 0,93 24Mg 143000 0,061 27Al 12900 7752,71 30Si 160000 42632,48 43Ca 13500 250,23 45Sc 8,64 0,97 51V 85 2,74 60Ni 16500 1,28 85Rb 3,45 30,78 88Sr 11,9 0,95 89Y 2,25 3,34 90Zr 5,54 12,66 93Nb 0,375 2,07 137Ba 3,41 6,16 139La 0,367 1,99 140Ce 0,957 3,72 141Pr 0,137 0,362 143Nd 0,711 1,35 147Sm 0,231 0,33 153Eu 0,087 <0.0074 157Gd 0,306 0,226 159Tb 0,058 0,033 163Dy 0,381 0,5 165Ho 0,0851 0,108 166Er 0,249 0,307 169Tm 0,0356 0,062 172Yb 0,248 0,329 175Lu 0,0381 0,087 178Hf 0,179 0,461 181Ta 0,026 0,217 208Pb 3,65 4,52 232Th 0,0425 3,26 238U 0,0122 0,725 REE Chondrite normalised BR-6_9 La 0,367 5,4223 Ce 0,957 3,8871 Pr 0,137 2,6423 Nd 0,711 1,8987 Sm 0,231 1,4286 Eu 0,087 Gd 0,306 0,7386 Tb 0,058 0,5690 Dy 0,381 1,3123 Ho 0,0851 1,2691 Er 0,249 1,2329 Tm 0,0356 1,7416 Yb 0,248 1,3266 Lu 0,0381 2,2835 161 Element Chondrite BTS-12_1 BTS-12_2 BTS-12_3 BTS-12_4 BTS-12_5 BTS- 12_6 BTS-12_7 BTS-12_8 9Be 0,04 <1.97 3,24 0,35 4,04 1,76 <3.52 1,42 2,31 24Mg 143000 0,054 0,054 0,054 0,054 0,054 0,054 0,054 0,054 27Al 12900 61429,39 55008,45 43304,85 63735,7 58540,45 57837,32 33632,83 57568,7 30Si 160000 231872,42 247096,03 222189,09 265561,31 242483,11 271451 159648,69 327175,81 43Ca 13500 2860,63 3082,43 2717,8 3500,35 4825,69 3572,6 821,45 4678,2 45Sc 8,64 3,4 3,26 2,85 4,1 4,35 3,17 2,32 3,92 51V 85 3,29 2,96 4,01 2,47 2,46 0,84 5,06 2,41 60Ni 16500 2 1,98 1,2 0,27 1,17 <0.72 <0.39 1,32 85Rb 3,45 179,63 175,12 153,66 201,72 174,65 197,57 116,25 227,7 88Sr 11,9 29,23 26,36 25,56 35,91 50,84 27,99 20,17 33,25 89Y 2,25 17,52 15,98 9,37 20,8 14,39 19,15 9,12 14,74 90Zr 5,54 48,73 55,47 41,79 68,03 45,39 48,34 44,25 45,64 93Nb 0,375 9,74 10,3 8,42 11,07 9,08 9,26 8,56 12,23 137Ba 3,41 324 277,54 336,62 349,93 425,46 282,99 200,28 360,07 139La 0,367 18,05 17,4 14,33 21,7 20,14 19,54 10,76 17,61 140Ce 0,957 36,17 34,39 33,96 41,13 40,12 39,75 19,84 44,31 141Pr 0,137 3,57 3,1 2,85 4,39 3,87 3,57 2,01 3,72 143Nd 0,711 13,84 12,02 9,29 15,25 12,84 12,71 6,95 11,61 147Sm 0,231 2,79 2,39 1,74 2,24 2,34 2,77 2,06 2,27 153Eu 0,087 0,27 0,25 0,217 0,258 0,409 0,312 0,124 0,321 157Gd 0,306 2,28 1,4 1,55 2,73 2,25 3,23 1,39 1,76 159Tb 0,058 0,3 0,425 0,23 0,49 0,398 0,542 0,255 0,382 163Dy 0,381 2,58 2,41 1,69 2,66 2,31 2,59 1,4 2,32 165Ho 0,0851 0,708 0,578 0,296 0,626 0,367 0,64 0,282 0,51 166Er 0,249 1,87 1,65 0,857 2,2 1,52 1,67 1 1,56 169Tm 0,0356 0,196 0,291 0,172 0,299 0,227 0,288 0,157 0,24 172Yb 0,248 2,76 2,3 1,41 2,64 2,2 2,25 0,94 1,79 175Lu 0,0381 0,338 0,335 0,193 0,383 0,281 0,39 0,163 0,274 178Hf 0,179 1,97 1,66 1,21 2,34 2,01 2,07 1,52 1,77 181Ta 0,026 0,97 0,892 0,66 1,02 0,81 0,93 0,546 1,043 208Pb 3,65 35,93 28,76 26,03 35,51 28,99 32,33 20,06 35,22 232Th 0,0425 18,5 16,16 11,72 20,79 17,51 19,56 10,41 17,16 238U 0,0122 4,13 3,38 2,99 4,3 3,33 4,27 2,42 4,87 REE Chondrite normalised BTS-12_1 BTS-12_2 BTS-12_3 BTS-12_4 BTS-12_5 BTS- 12_6 BTS-12_7 BTS-12_8 La 0,367 49,1826 47,4114 39,0463 59,1281 54,8774 53,2425 29,3188 47,9837 Ce 0,957 37,7952 35,9352 35,4859 42,9781 41,9227 41,5361 20,7315 46,3009 Pr 0,137 26,0584 22,6277 20,8029 32,0438 28,2482 26,0584 14,6715 27,1533 Nd 0,711 19,4655 16,9058 13,0661 21,4487 18,0591 17,8762 9,7750 16,3291 Sm 0,231 12,0779 10,3463 7,5325 9,6970 10,1299 11,9913 8,9177 9,8268 Eu 0,087 3,1034 2,8736 2,4943 2,9655 4,7011 3,5862 1,4253 3,6897 Gd 0,306 7,4510 4,5752 5,0654 8,9216 7,3529 10,5556 4,5425 5,7516 Tb 0,058 5,1724 7,3276 3,9655 8,4483 6,8621 9,3448 4,3966 6,5862 Dy 0,381 6,7717 6,3255 4,4357 6,9816 6,0630 6,7979 3,6745 6,0892 Ho 0,0851 8,3196 6,7920 3,4783 7,3561 4,3126 7,5206 3,3137 5,9929 Er 0,249 7,5100 6,6265 3,4418 8,8353 6,1044 6,7068 4,0161 6,2651 Tm 0,0356 5,5056 8,1742 4,8315 8,3989 6,3764 8,0899 4,4101 6,7416 Yb 0,248 11,1290 9,2742 5,6855 10,6452 8,8710 9,0726 3,7903 7,2177 Lu 0,0381 8,8714 8,7927 5,0656 10,0525 7,3753 10,2362 4,2782 7,1916 162 Element Chondrite BTS-12_9 BTS-12_10 9Be 0,04 0,83 <0.00 24Mg 143000 0,054 0,054 27Al 12900 48309,7 31068,77 30Si 160000 218671,78 85964,74 43Ca 13500 3401,28 510,14 45Sc 8,64 3,01 2,09 51V 85 8,12 7,71 60Ni 16500 0,67 3,41 85Rb 3,45 154,42 56,87 88Sr 11,9 23,74 5,72 89Y 2,25 14,85 4,05 90Zr 5,54 45,16 31,73 93Nb 0,375 9,68 7,57 137Ba 3,41 246,06 65,83 139La 0,367 15,92 5,86 140Ce 0,957 32,26 10,3 141Pr 0,137 3,3 1,2 143Nd 0,711 12,9 3,39 147Sm 0,231 2,03 0,44 153Eu 0,087 0,161 0,225 157Gd 0,306 2,12 0,57 159Tb 0,058 0,365 0,068 163Dy 0,381 2,65 1,14 165Ho 0,0851 0,53 0,216 166Er 0,249 1,49 0,69 169Tm 0,0356 0,222 0,104 172Yb 0,248 1,72 0,77 175Lu 0,0381 0,278 0,098 178Hf 0,179 1,87 1,12 181Ta 0,026 0,905 0,556 208Pb 3,65 58,09 18,51 232Th 0,0425 23,29 6,94 238U 0,0122 4,23 1,65 REE Chondrite li d BTS-12_9 BTS-12_10 La 0,367 43,3787 15,9673 Ce 0,957 33,7095 10,7628 Pr 0,137 24,0876 8,7591 Nd 0,711 18,1435 4,7679 Sm 0,231 8,7879 1,9048 Eu 0,087 1,8506 2,5862 Gd 0,306 6,9281 1,8627 Tb 0,058 6,2931 1,1724 Dy 0,381 6,9554 2,9921 Ho 0,0851 6,2280 2,5382 Er 0,249 5,9839 2,7711 Tm 0,0356 6,2360 2,9213 Yb 0,248 6,9355 3,1048 Lu 0,0381 7,2966 2,5722 163 Element Chondrite BTS-12_1 BTS-12_2 BTS-12_3 BTS-12_4 BTS-12_5 BTS- 12_6 BTS-12_7 BTS-12_8 9Be 0,04 <1.97 3,24 0,35 4,04 1,76 <3.52 1,42 2,31 24Mg 143000 0,054 0,054 0,054 0,054 0,054 0,054 0,054 0,054 27Al 12900 61429,39 55008,45 43304,85 63735,7 58540,45 57837,32 33632,83 57568,7 30Si 160000 231872,42 247096,03 222189,09 265561,31 242483,11 271451 159648,69 327175,81 43Ca 13500 2860,63 3082,43 2717,8 3500,35 4825,69 3572,6 821,45 4678,2 45Sc 8,64 3,4 3,26 2,85 4,1 4,35 3,17 2,32 3,92 51V 85 3,29 2,96 4,01 2,47 2,46 0,84 5,06 2,41 60Ni 16500 2 1,98 1,2 0,27 1,17 <0.72 <0.39 1,32 85Rb 3,45 179,63 175,12 153,66 201,72 174,65 197,57 116,25 227,7 88Sr 11,9 29,23 26,36 25,56 35,91 50,84 27,99 20,17 33,25 89Y 2,25 17,52 15,98 9,37 20,8 14,39 19,15 9,12 14,74 90Zr 5,54 48,73 55,47 41,79 68,03 45,39 48,34 44,25 45,64 93Nb 0,375 9,74 10,3 8,42 11,07 9,08 9,26 8,56 12,23 137Ba 3,41 324 277,54 336,62 349,93 425,46 282,99 200,28 360,07 139La 0,367 18,05 17,4 14,33 21,7 20,14 19,54 10,76 17,61 140Ce 0,957 36,17 34,39 33,96 41,13 40,12 39,75 19,84 44,31 141Pr 0,137 3,57 3,1 2,85 4,39 3,87 3,57 2,01 3,72 143Nd 0,711 13,84 12,02 9,29 15,25 12,84 12,71 6,95 11,61 147Sm 0,231 2,79 2,39 1,74 2,24 2,34 2,77 2,06 2,27 153Eu 0,087 0,27 0,25 0,217 0,258 0,409 0,312 0,124 0,321 157Gd 0,306 2,28 1,4 1,55 2,73 2,25 3,23 1,39 1,76 159Tb 0,058 0,3 0,425 0,23 0,49 0,398 0,542 0,255 0,382 163Dy 0,381 2,58 2,41 1,69 2,66 2,31 2,59 1,4 2,32 165Ho 0,0851 0,708 0,578 0,296 0,626 0,367 0,64 0,282 0,51 166Er 0,249 1,87 1,65 0,857 2,2 1,52 1,67 1 1,56 169Tm 0,0356 0,196 0,291 0,172 0,299 0,227 0,288 0,157 0,24 172Yb 0,248 2,76 2,3 1,41 2,64 2,2 2,25 0,94 1,79 175Lu 0,0381 0,338 0,335 0,193 0,383 0,281 0,39 0,163 0,274 178Hf 0,179 1,97 1,66 1,21 2,34 2,01 2,07 1,52 1,77 181Ta 0,026 0,97 0,892 0,66 1,02 0,81 0,93 0,546 1,043 208Pb 3,65 35,93 28,76 26,03 35,51 28,99 32,33 20,06 35,22 232Th 0,0425 18,5 16,16 11,72 20,79 17,51 19,56 10,41 17,16 238U 0,0122 4,13 3,38 2,99 4,3 3,33 4,27 2,42 4,87 REE Chondrite normalised BTS-12_1 BTS-12_2 BTS-12_3 BTS-12_4 BTS-12_5 BTS- 12_6 BTS-12_7 BTS-12_8 La 0,367 49,1826 47,4114 39,0463 59,1281 54,8774 53,2425 29,3188 47,9837 Ce 0,957 37,7952 35,9352 35,4859 42,9781 41,9227 41,5361 20,7315 46,3009 Pr 0,137 26,0584 22,6277 20,8029 32,0438 28,2482 26,0584 14,6715 27,1533 Nd 0,711 19,4655 16,9058 13,0661 21,4487 18,0591 17,8762 9,7750 16,3291 Sm 0,231 12,0779 10,3463 7,5325 9,6970 10,1299 11,9913 8,9177 9,8268 Eu 0,087 3,1034 2,8736 2,4943 2,9655 4,7011 3,5862 1,4253 3,6897 Gd 0,306 7,4510 4,5752 5,0654 8,9216 7,3529 10,5556 4,5425 5,7516 Tb 0,058 5,1724 7,3276 3,9655 8,4483 6,8621 9,3448 4,3966 6,5862 Dy 0,381 6,7717 6,3255 4,4357 6,9816 6,0630 6,7979 3,6745 6,0892 Ho 0,0851 8,3196 6,7920 3,4783 7,3561 4,3126 7,5206 3,3137 5,9929 Er 0,249 7,5100 6,6265 3,4418 8,8353 6,1044 6,7068 4,0161 6,2651 Tm 0,0356 5,5056 8,1742 4,8315 8,3989 6,3764 8,0899 4,4101 6,7416 Yb 0,248 11,1290 9,2742 5,6855 10,6452 8,8710 9,0726 3,7903 7,2177 Lu 0,0381 8,8714 8,7927 5,0656 10,0525 7,3753 10,2362 4,2782 7,1916 164 Element Chondrite KgL12_1 KgL12_2 KgL12_3 KgL12_4 KgL12_5 KgL12_6 KgL12_7 KgL12_8 9Be 0,04 11,2 3,03 1,43 0,86 41,4 3,67 6,84 <0.00 24Mg 143000 0,068 0,068 0,068 0,068 0,068 0,068 0,068 0,068 27Al 12900 1191297,63 91027,41 48189,48 38231,59 1489432,88 93462,54 100810,88 31128,4 30Si 160000 1526008,13 379958,97 165830,5 177215,69 3272651 456228,66 535000,88 149284,02 43Ca 13500 350575,91 5193,57 2613,11 3062,11 427525,97 6579,62 4992,53 3302,24 45Sc 8,64 25,82 5,97 2,6 2,57 24,93 6,07 6,69 <1.56 51V 85 <5.69 2,66 5,19 1,88 <8.87 1,57 1,57 15,41 60Ni 16500 3,42 1,44 1,23 0,3 14,06 0,8 <0.65 <1.01 85Rb 3,45 15,68 430,9 141,85 150,28 24,2 426,44 493,2 132,57 88Sr 11,9 3280,7 21,38 21,83 23,16 4014,16 38,1 25,04 8,58 89Y 2,25 1,83 39,86 11,52 10,8 2,54 32,91 41,48 12,42 90Zr 5,54 <0.00 73,48 49,71 32,4 3,14 81 83,44 39,48 93Nb 0,375 0,21 22,56 9,32 8,01 <0.40 19,34 24,82 6,17 137Ba 3,41 1807,22 82,67 209,06 232,9 2317,68 253,94 80,98 149,62 139La 0,367 64,69 22,61 11,43 12,58 85,12 27,91 26,23 10,58 140Ce 0,957 91,18 54,95 26,66 28,43 127,01 65,05 66,59 19,89 141Pr 0,137 6,66 5,7 2,47 2,49 9,22 5,76 6,64 2,68 143Nd 0,711 17,86 20,87 7,84 8,94 27,1 20,44 22,76 5,38 147Sm 0,231 2 4,04 1,91 1,56 1,91 4,87 5,74 1,02 153Eu 0,087 13,72 0,316 0,256 0,19 20,42 0,388 0,255 0,138 157Gd 0,306 1,36 4,43 1,57 1,38 2,52 4,65 4,96 1,3 159Tb 0,058 0,172 0,887 0,262 0,258 <0.00 0,922 0,918 0,36 163Dy 0,381 0,96 6,2 1,72 1,67 0,34 5,14 7,03 1,93 165Ho 0,0851 0,072 1,44 0,384 0,345 <0.21 1,15 1,59 0,38 166Er 0,249 <0.00 4,59 1,22 1,18 <0.72 3,64 4,46 0,89 169Tm 0,0356 <0.05 0,702 0,214 0,181 0,02 0,587 0,834 0,204 172Yb 0,248 0,077 6,25 1,81 1,53 <0.45 4,8 5,85 1,61 175Lu 0,0381 <0.06 0,793 0,265 0,23 0,084 0,696 0,858 0,261 178Hf 0,179 <0.274 3,62 1,88 1,3 <0.49 3,69 3,71 1,2 181Ta 0,026 <0.063 2,34 0,911 0,737 <0.112 1,94 2,47 0,66 208Pb 3,65 132,86 59,1 28,55 23,85 251,9 54,74 65,93 15,81 232Th 0,0425 <0.168 39,5 11,96 12,51 0,09 34,26 43,76 12,58 238U 0,0122 0,055 10,34 3,14 2,98 <0.23 8,72 12,26 2,82 REE Chondrite normalised KgL12_1 KgL12_2 KgL12_3 KgL12_4 KgL12_5 KgL12_6 KgL12_7 KgL12_8 La 0,367 176,2670 61,6076 31,1444 34,2779 231,9346 76,0490 71,4714 28,8283 Ce 0,957 95,2769 57,4190 27,8579 29,7074 132,7168 67,9728 69,5820 20,7837 Pr 0,137 48,6131 41,6058 18,0292 18,1752 67,2993 42,0438 48,4672 19,5620 Nd 0,711 25,1195 29,3530 11,0267 12,5738 38,1153 28,7482 32,0113 7,5668 Sm 0,231 8,6580 17,4892 8,2684 6,7532 8,2684 21,0823 24,8485 4,4156 Eu 0,087 157,7011 3,6322 2,9425 2,1839 234,7126 4,4598 2,9310 1,5862 Gd 0,306 4,4444 14,4771 5,1307 4,5098 8,2353 15,1961 16,2092 4,2484 Tb 0,058 2,9655 15,2931 4,5172 4,4483 15,8966 15,8276 6,2069 Dy 0,381 2,5197 16,2730 4,5144 4,3832 0,8924 13,4908 18,4514 5,0656 Ho 0,0851 0,8461 16,9213 4,5123 4,0541 13,5135 18,6839 4,4653 Er 0,249 18,4337 4,8996 4,7390 14,6185 17,9116 3,5743 Tm 0,0356 19,7191 6,0112 5,0843 0,5618 16,4888 23,4270 5,7303 Yb 0,248 0,3105 25,2016 7,2984 6,1694 19,3548 23,5887 6,4919 Lu 0,0381 20,8136 6,9554 6,0367 2,2047 18,2677 22,5197 6,8504 165 Element Chondrite KgL12_9 KgL12_10 9Be 0,04 <0.00 1,64 24Mg 143000 0,068 0,068 27Al 12900 61425,49 79806,89 30Si 160000 300646 437419,03 43Ca 13500 5279,03 5302,63 45Sc 8,64 3,24 5,92 51V 85 1,99 1,76 60Ni 16500 <0.79 0,7 85Rb 3,45 231,69 329,27 88Sr 11,9 42,48 35,41 89Y 2,25 20,49 28,53 90Zr 5,54 82,73 82,31 93Nb 0,375 11,15 16,26 137Ba 3,41 401,44 287,24 139La 0,367 24,93 23,98 140Ce 0,957 47,65 56,26 141Pr 0,137 4,43 5 143Nd 0,711 18,69 18,4 147Sm 0,231 3,92 3,78 153Eu 0,087 0,26 0,381 157Gd 0,306 1,65 3,23 159Tb 0,058 0,45 0,716 163Dy 0,381 2,36 4,42 165Ho 0,0851 0,78 0,949 166Er 0,249 2,05 2,77 169Tm 0,0356 0,397 0,504 172Yb 0,248 3,06 3,85 175Lu 0,0381 0,431 0,505 178Hf 0,179 2,64 3 181Ta 0,026 1,08 1,56 208Pb 3,65 32,26 50,39 232Th 0,0425 21,21 29,85 238U 0,0122 4,76 7,48 REE Chondrite normalised KgL12_9 KgL12_10 La 0,367 67,9292 65,3406 Ce 0,957 49,7910 58,7879 Pr 0,137 32,3358 36,4964 Nd 0,711 26,2869 25,8790 Sm 0,231 16,9697 16,3636 Eu 0,087 2,9885 4,3793 Gd 0,306 5,3922 10,5556 Tb 0,058 7,7586 12,3448 Dy 0,381 6,1942 11,6010 Ho 0,0851 9,1657 11,1516 Er 0,249 8,2329 11,1245 Tm 0,0356 11,1517 14,1573 Yb 0,248 12,3387 15,5242 Lu 0,0381 11,3123 13,2546 166 Element Chondrite KgL3-3_1 KgL3-3_2 KgL3-3_3 KgL3-3_4 KgL3-3_5 KgL3-3_6 KgL3-3_7 KgL3-3_8 9Be 0,04 0,81 1,91 <0.00 <0.00 0,51 3,45 <5.88 6,6 24Mg 143000 0,063 0,063 0,063 0,063 0,063 0,063 0,063 0,063 27Al 12900 83014,59 64046,21 78282,66 67539,83 47604,82 78570,35 71522,09 61870,35 30Si 160000 336167,19 299783,53 303185,25 269569,91 141334,36 371288,25 304988,19 276797,34 43Ca 13500 6349,68 5117,94 7054,62 3588,28 2175,33 4927,87 4093,82 5105,94 45Sc 8,64 4,47 2,92 4,04 3,48 2,32 3,24 3 3,41 51V 85 1,09 0,7 1,66 3,69 5,25 1,83 <1.18 2,26 60Ni 16500 1,03 0,58 1,4 3,33 3,66 0,7 <1.20 22,88 85Rb 3,45 284,74 220,17 263,42 246,38 93,93 309,22 207,33 199,43 88Sr 11,9 47,55 44,04 38,92 10,36 11,95 29,76 46,59 43,46 89Y 2,25 26,97 18,91 24,75 25,06 7,89 30,08 20,17 15,66 90Zr 5,54 90,8 58,64 82 54,48 38,36 69,04 54,03 60,12 93Nb 0,375 14,44 12,01 15,52 14 8,31 15,22 11,04 11,07 137Ba 3,41 476,11 549,93 447,21 66,38 164,35 247,21 540,4 462,15 139La 0,367 30,39 26,19 26,02 15,39 9,2 24,74 26,57 21,99 140Ce 0,957 58,65 52,26 52,75 34,68 24,82 52,26 49,34 45,94 141Pr 0,137 5,53 4,77 4,67 3,52 1,9 5,16 4,65 3,93 143Nd 0,711 19,9 16,3 15,01 11,57 6,25 19,2 14,73 13,82 147Sm 0,231 3,73 2,8 4,56 2,85 1,36 3,24 3,72 3,14 153Eu 0,087 0,345 0,404 0,353 0,166 0,197 0,226 0,408 0,266 157Gd 0,306 3,39 2,63 2,28 2,6 0,98 4,16 2,41 3,15 159Tb 0,058 0,686 0,485 0,7 0,561 0,202 0,71 0,512 0,426 163Dy 0,381 4,04 2,67 3,24 3,71 1,41 5,01 3,11 2,85 165Ho 0,0851 1,09 0,622 0,81 0,852 0,257 1,11 0,741 0,66 166Er 0,249 3,01 2,01 2,51 2,6 0,788 3,26 2,06 1,74 169Tm 0,0356 0,56 0,309 0,444 0,437 0,138 0,601 0,294 0,222 172Yb 0,248 3,68 2,7 2,81 3,43 0,876 4,44 2,58 2,31 175Lu 0,0381 0,593 0,42 0,413 0,496 0,136 0,695 0,406 0,364 178Hf 0,179 2,97 2,31 3,17 2,56 1,39 3,28 2,61 2,49 181Ta 0,026 1,31 1,12 1,3 1,68 0,784 1,55 1,08 1,06 208Pb 3,65 44,24 36,37 40,61 39,21 19,42 47,38 32,36 32,32 232Th 0,0425 28,13 21,14 27,29 25,88 11,25 30,55 21,92 19,65 238U 0,0122 5,43 4,28 5,08 5,82 2,15 7,25 3,73 4,02 REE Chondrite normalised KgL3-3_1 KgL3-3_2 KgL3-3_3 KgL3-3_4 KgL3-3_5 KgL3-3_6 KgL3-3_7 KgL3-3_8 La 0,367 82,8065 71,3624 70,8992 41,9346 25,0681 67,4114 72,3978 59,9183 Ce 0,957 61,2853 54,6082 55,1202 36,2382 25,9352 54,6082 51,5569 48,0042 Pr 0,137 40,3650 34,8175 34,0876 25,6934 13,8686 37,6642 33,9416 28,6861 Nd 0,711 27,9887 22,9255 21,1111 16,2729 8,7904 27,0042 20,7173 19,4374 Sm 0,231 16,1472 12,1212 19,7403 12,3377 5,8874 14,0260 16,1039 13,5931 Eu 0,087 3,9655 4,6437 4,0575 1,9080 2,2644 2,5977 4,6897 3,0575 Gd 0,306 11,0784 8,5948 7,4510 8,4967 3,2026 13,5948 7,8758 10,2941 Tb 0,058 11,8276 8,3621 12,0690 9,6724 3,4828 12,2414 8,8276 7,3448 Dy 0,381 10,6037 7,0079 8,5039 9,7375 3,7008 13,1496 8,1627 7,4803 Ho 0,0851 12,8085 7,3090 9,5182 10,0118 3,0200 13,0435 8,7074 7,7556 Er 0,249 12,0884 8,0723 10,0803 10,4418 3,1647 13,0924 8,2731 6,9880 Tm 0,0356 15,7303 8,6798 12,4719 12,2753 3,8764 16,8820 8,2584 6,2360 Yb 0,248 14,8387 10,8871 11,3306 13,8306 3,5323 17,9032 10,4032 9,3145 Lu 0,0381 15,5643 11,0236 10,8399 13,0184 3,5696 18,2415 10,6562 9,5538 167 Element Chondrite KgL3-3_9 KgL3-3_10 9Be 0,04 <0.00 4,3 24Mg 143000 0,063 0,063 27Al 12900 67715,77 96041,64 30Si 160000 330481,94 493351,19 43Ca 13500 4487,56 5980,42 45Sc 8,64 4,11 5,26 51V 85 1,05 <1.21 60Ni 16500 1,15 2,38 85Rb 3,45 248,44 391,95 88Sr 11,9 36,51 35,24 89Y 2,25 21,01 34,43 90Zr 5,54 67,25 91,89 93Nb 0,375 11,44 19,53 137Ba 3,41 392,88 209,82 139La 0,367 24,94 26,35 140Ce 0,957 46,81 59,23 141Pr 0,137 4,57 5,5 143Nd 0,711 18,85 19,4 147Sm 0,231 2,15 4,63 153Eu 0,087 0,33 0,41 157Gd 0,306 2,64 3,52 159Tb 0,058 0,339 0,8 163Dy 0,381 3,65 4,77 165Ho 0,0851 0,76 1,23 166Er 0,249 2,49 3,31 169Tm 0,0356 0,457 0,659 172Yb 0,248 2,76 4,86 175Lu 0,0381 0,462 0,702 178Hf 0,179 2,36 3,47 181Ta 0,026 1,02 1,83 208Pb 3,65 34,74 59,23 232Th 0,0425 24,02 36,32 238U 0,0122 4,87 8,85 REE Chondrite li d KgL3-3_9 KgL3-3_10 La 0,367 67,9564 71,7984 Ce 0,957 48,9133 61,8913 Pr 0,137 33,3577 40,1460 Nd 0,711 26,5120 27,2855 Sm 0,231 9,3074 20,0433 Eu 0,087 3,7931 4,7126 Gd 0,306 8,6275 11,5033 Tb 0,058 5,8448 13,7931 Dy 0,381 9,5801 12,5197 Ho 0,0851 8,9307 14,4536 Er 0,249 10,0000 13,2932 Tm 0,0356 12,8371 18,5112 Yb 0,248 11,1290 19,5968 Lu 0,0381 12,1260 18,4252 168 Element Chondrite 3-11_1 3-11_2 3-11_3 3-11_4 3-11_5 3-11_6 3-11_7 3-11_8 9Be 0,04 0,85 2,59 2,5 1,58 <0.00 5,15 1,99 0,75 24Mg 143000 0,048 0,048 0,048 0,048 0,048 0,048 0,048 0,048 27Al 12900 37566,18 49978,39 64344,36 65758,44 16128,25 71707,49 45313,56 24089,62 30Si 160000 159453,42 247240,89 283282,56 347963,97 71822,57 428851,84 214428,95 108430,84 43Ca 13500 2448,7 3571,37 4045,87 4321,29 1209,85 4660,29 2823,78 1852,32 45Sc 8,64 1,8 3,13 4,21 4,12 0,86 5,34 3,18 1,39 51V 85 1,07 0,7 0,81 1,04 0,85 <0.57 0,72 0,57 60Ni 16500 0,39 0,68 <0.94 <0.43 <0.34 1,26 0,35 0,39 85Rb 3,45 138,77 262,57 280,21 349,21 75,48 399,71 206,14 94,83 88Sr 11,9 21,14 9,66 13,89 14,05 5,98 15,55 9,39 15,34 89Y 2,25 11,38 20,5 28,12 28,02 7,91 28,88 20,77 7,38 90Zr 5,54 32 42,48 60,33 52,53 16,76 58,61 36,39 20,59 93Nb 0,375 6,87 13,11 14,34 17,18 3,86 20,68 10,29 4,15 137Ba 3,41 223,61 45,4 47,49 52,89 16,49 51,57 39,58 140,54 139La 0,367 11,76 13,27 16,86 16,87 5 18,65 12,4 8,43 140Ce 0,957 25,56 33,64 38,53 45,15 10,6 53,62 28,1 17,61 141Pr 0,137 2,36 3,37 4,13 4,25 1,18 4,81 2,73 1,49 143Nd 0,711 7,63 11,86 13,99 14,38 4,27 16,33 10,42 5,29 147Sm 0,231 1,64 3,06 3,32 3,72 1,31 3,88 2,16 0,93 153Eu 0,087 0,214 0,128 0,067 0,189 0,037 0,192 0,109 0,129 157Gd 0,306 1,48 3,03 2,94 3,73 1,42 3,78 2,1 1,24 159Tb 0,058 0,252 0,483 0,613 0,659 0,164 0,661 0,453 0,118 163Dy 0,381 1,63 3,47 4,34 4,2 1,51 4,45 3,47 1,29 165Ho 0,0851 0,396 0,853 0,96 0,918 0,303 0,98 0,714 0,277 166Er 0,249 1,14 2,35 3,21 3,03 0,8 3,07 1,9 0,751 169Tm 0,0356 0,208 0,412 0,509 0,481 0,168 0,543 0,36 0,149 172Yb 0,248 1,47 3,1 4,04 3,91 1,13 4,14 2,71 1,05 175Lu 0,0381 0,231 0,452 0,554 0,57 0,175 0,571 0,424 0,157 178Hf 0,179 1,24 1,91 2,39 2,41 0,74 2,65 1,8 0,79 181Ta 0,026 0,595 1,36 1,5 1,77 0,456 2,08 1,152 0,412 208Pb 3,65 20,56 34,52 39,96 44,45 10,54 56,16 28,98 14,49 232Th 0,0425 11,08 20,15 26,98 26,97 8,39 29,43 20,46 8,27 238U 0,0122 2,42 5,78 6,85 8,36 1,87 9,99 5,01 1,88 REE Chondrite normalised 3-11_1 3-11_2 3-11_3 3-11_4 3-11_5 3-11_6 3-11_7 3-11_8 La 0,367 32,0436 36,1580 45,9401 45,9673 13,6240 50,8174 33,7875 22,9700 Ce 0,957 26,7085 35,1515 40,2612 47,1787 11,0763 56,0293 29,3626 18,4013 Pr 0,137 17,2263 24,5985 30,1460 31,0219 8,6131 35,1095 19,9270 10,8759 Nd 0,711 10,7314 16,6807 19,6765 20,2250 6,0056 22,9677 14,6554 7,4402 Sm 0,231 7,0996 13,2468 14,3723 16,1039 5,6710 16,7965 9,3506 4,0260 Eu 0,087 2,4598 1,4713 0,7701 2,1724 0,4253 2,2069 1,2529 1,4828 Gd 0,306 4,8366 9,9020 9,6078 12,1895 4,6405 12,3529 6,8627 4,0523 Tb 0,058 4,3448 8,3276 10,5690 11,3621 2,8276 11,3966 7,8103 2,0345 Dy 0,381 4,2782 9,1076 11,3911 11,0236 3,9633 11,6798 9,1076 3,3858 Ho 0,0851 4,6533 10,0235 11,2808 10,7873 3,5605 11,5159 8,3901 3,2550 Er 0,249 4,5783 9,4378 12,8916 12,1687 3,2129 12,3293 7,6305 3,0161 Tm 0,0356 5,8427 11,5730 14,2978 13,5112 4,7191 15,2528 10,1124 4,1854 Yb 0,248 5,9274 12,5000 16,2903 15,7661 4,5565 16,6935 10,9274 4,2339 Lu 0,0381 6,0630 11,8635 14,5407 14,9606 4,5932 14,9869 11,1286 4,1207 169 Element Chondrite 3-11_9 3-11_10 9Be 0,04 1,52 2,7 24Mg 143000 0,048 0,048 27Al 12900 30752,85 57877,44 30Si 160000 172193,23 306834,03 43Ca 13500 2084,95 3720,14 45Sc 8,64 1,89 4,02 51V 85 1,14 <0.42 60Ni 16500 0,31 0,92 85Rb 3,45 162,87 303,21 88Sr 11,9 5,64 11,52 89Y 2,25 13,4 25,27 90Zr 5,54 28,99 49,51 93Nb 0,375 8,21 14,7 137Ba 3,41 34,24 49,17 139La 0,367 8,29 15,4 140Ce 0,957 21,36 39,93 141Pr 0,137 1,95 3,77 143Nd 0,711 7,28 13,26 147Sm 0,231 1,62 2,89 153Eu 0,087 0,088 0,208 157Gd 0,306 1,37 3,17 159Tb 0,058 0,315 0,606 163Dy 0,381 1,85 3,49 165Ho 0,0851 0,475 0,93 166Er 0,249 1,54 2,87 169Tm 0,0356 0,236 0,487 172Yb 0,248 1,69 3,69 175Lu 0,0381 0,27 0,594 178Hf 0,179 0,952 2,23 181Ta 0,026 0,864 1,48 208Pb 3,65 21,85 42,98 232Th 0,0425 12,72 25,3 238U 0,0122 3,85 7,07 REE Chondrite normalised 3-11_9 3-11_10 La 0,367 22,5886 41,9619 Ce 0,957 22,3197 41,7241 Pr 0,137 14,2336 27,5182 Nd 0,711 10,2391 18,6498 Sm 0,231 7,0130 12,5108 Eu 0,087 1,0115 2,3908 Gd 0,306 4,4771 10,3595 Tb 0,058 5,4310 10,4483 Dy 0,381 4,8556 9,1601 Ho 0,0851 5,5817 10,9283 Er 0,249 6,1847 11,5261 Tm 0,0356 6,6292 13,6798 Yb 0,248 6,8145 14,8790 Lu 0,0381 7,0866 15,5906 170 Element Chondrite BTS-3_1 BTS-3_2 BTS-3_3 BTS-3_4 BTS-3_5 BTS- 3_6 BTS-3_7 BTS-3_8 9Be 0,04 0,52 4,23 <3.66 1,47 2,77 4 1,98 1,96 24Mg 143000 0,063 0,063 0,063 0,063 0,063 0,063 0,063 0,063 27Al 12900 70759,88 70112,55 83521,98 71562,75 83221,66 98612,5 43989,51 85444,43 30Si 160000 321600,16 339781,19 405928,16 364738,38 413469 420279 203376,53 390209,31 43Ca 13500 4646,78 5729,48 5158,71 5132,58 5358,65 5291,92 2411,33 6053,06 45Sc 8,64 3,81 2,56 4,68 3,64 5,33 5,9 2,02 5,39 51V 85 0,85 3,65 1,24 0,99 1,92 1,72 3,79 <1.04 60Ni 16500 0,48 <1.17 <0.53 0,52 1,13 0,54 0,97 0,8 85Rb 3,45 253,4 280,02 280,68 268,84 402,62 418,26 161,88 326,19 88Sr 11,9 41,9 39,04 47,47 46,28 18,13 20,76 15,38 36,25 89Y 2,25 20,93 22,85 25,39 21,99 39,46 47,34 14,08 30,78 90Zr 5,54 55,43 55,83 78,93 65,81 75,58 85,02 44,11 74,19 93Nb 0,375 13,11 13,99 15,25 12,89 19,5 21,18 9,02 15,97 137Ba 3,41 395,84 402,48 476,53 423,36 59,5 76,77 148,92 279,37 139La 0,367 22,84 22,74 27,76 23,88 20,84 25,98 12,54 25,63 140Ce 0,957 51,64 48,17 57,36 52,9 52,48 55,92 24,76 54,24 141Pr 0,137 4,68 4,29 5,05 4,77 4,92 5,77 2,49 5,31 143Nd 0,711 16,62 14,95 18,82 16,53 20,65 23,44 9,32 16,96 147Sm 0,231 2,9 2,68 3,85 3,16 5,22 5,81 1,9 3,42 153Eu 0,087 0,329 0,6 0,384 0,325 0,27 0,244 0,158 0,204 157Gd 0,306 2,92 2,67 4,34 2,85 4,68 4,44 1,14 3,21 159Tb 0,058 0,502 0,57 0,712 0,593 0,854 1,07 0,342 0,566 163Dy 0,381 2,99 2,89 3,61 3,4 5,41 6,78 1,88 5,42 165Ho 0,0851 0,83 0,82 0,87 0,737 1,04 1,54 0,44 1,06 166Er 0,249 2,21 2,05 2,75 2,27 3,67 4,37 1,66 3,01 169Tm 0,0356 0,353 0,353 0,558 0,339 0,666 0,834 0,256 0,568 172Yb 0,248 2,81 2,83 3,42 3,19 5,09 5,6 1,63 4,41 175Lu 0,0381 0,433 0,478 0,466 0,459 0,712 0,99 0,27 0,542 178Hf 0,179 2,16 2,28 2,84 2,42 3,16 3,95 1,48 3,38 181Ta 0,026 1,26 1,13 1,23 1,23 2,14 2,46 0,997 1,67 208Pb 3,65 37,72 38,21 44,52 39,85 55,36 55,71 25,28 47,69 232Th 0,0425 21,64 22,27 25,63 21,65 35,36 40,45 14,08 31,28 238U 0,0122 4,96 5,61 5,42 5,06 9,69 9,59 3,33 6,78 REE Chondrite normalised BTS-3_1 BTS-3_2 BTS-3_3 BTS-3_4 BTS-3_5 BTS- 3_6 BTS-3_7 BTS-3_8 La 0,367 62,2343 61,9619 75,6403 65,0681 56,7847 70,7902 34,1689 69,8365 Ce 0,957 53,9603 50,3344 59,9373 55,2769 54,8380 58,4326 25,8725 56,6771 Pr 0,137 34,1606 31,3139 36,8613 34,8175 35,9124 42,1168 18,1752 38,7591 Nd 0,711 23,3755 21,0267 26,4698 23,2489 29,0436 32,9677 13,1083 23,8537 Sm 0,231 12,5541 11,6017 16,6667 13,6797 22,5974 25,1515 8,2251 14,8052 Eu 0,087 3,7816 6,8966 4,4138 3,7356 3,1034 2,8046 1,8161 2,3448 Gd 0,306 9,5425 8,7255 14,1830 9,3137 15,2941 14,5098 3,7255 10,4902 Tb 0,058 8,6552 9,8276 12,2759 10,2241 14,7241 18,4483 5,8966 9,7586 Dy 0,381 7,8478 7,5853 9,4751 8,9239 14,1995 17,7953 4,9344 14,2257 Ho 0,0851 9,7532 9,6357 10,2233 8,6604 12,2209 18,0964 5,1704 12,4559 Er 0,249 8,8755 8,2329 11,0442 9,1165 14,7390 17,5502 6,6667 12,0884 Tm 0,0356 9,9157 9,9157 15,6742 9,5225 18,7079 23,4270 7,1910 15,9551 Yb 0,248 11,3306 11,4113 13,7903 12,8629 20,5242 22,5806 6,5726 17,7823 Lu 0,0381 11,3648 12,5459 12,2310 12,0472 18,6877 25,9843 7,0866 14,2257 171 Element Chondrite Tej_1 Tej_2 Tej_3 Tej_4 Tej_5 Tej_6 Tej_7 Tej_8 9Be 0,04 <0.00 <0.00 2,55 0,47 1,1 1,19 <0.00 1,5 24Mg 143000 0,051 0,051 0,051 0,051 0,051 0,051 0,051 0,051 27Al 12900 57090,16 35581,34 39867,28 54155,83 57321,8 47089,06 62228,83 47418,52 30Si 160000 200934,73 133032,95 188143,14 273206,63 240237,39 216830,69 277115,88 234805,47 43Ca 13500 4802,09 2440,08 2847,88 4492,16 4564,36 2746,55 4797,75 2688,03 45Sc 8,64 3,4 1,88 2,5 3,13 3,05 1,45 1,64 2,27 51V 85 0,89 2,22 1,85 0,93 1,46 0,81 2,06 1,3 60Ni 16500 0,59 0,51 0,78 <0.54 0,45 0,65 0,98 0,61 85Rb 3,45 164,71 103,42 139,43 176,29 186,97 139,88 244,79 175,02 88Sr 11,9 28,53 17,4 24,12 39,4 25,61 32,87 31,96 22,7 89Y 2,25 16,57 10,64 11,84 13,87 17,95 13,03 20,08 17,46 90Zr 5,54 42,73 33,32 34,84 52,03 50,15 41,06 55,28 43,71 93Nb 0,375 7,96 5,56 6,85 8,82 9,56 6,77 10,85 8,39 137Ba 3,41 281,07 189,89 229,15 429,66 308,72 360,61 280,38 151,08 139La 0,367 17,22 11,3 12,75 18,78 18,36 17,48 20,53 14,5 140Ce 0,957 33,5 22,08 26,97 40,24 36,43 32,56 43,42 29,61 141Pr 0,137 2,91 2,16 2,57 3,48 3,78 3,24 4,07 2,98 143Nd 0,711 11,24 7,56 9,46 10,6 13,3 9,96 14,27 11,43 147Sm 0,231 1,74 1,52 1,87 2,78 2,68 2 2,44 1,88 153Eu 0,087 0,105 0,161 0,169 0,302 0,255 0,311 0,25 0,25 157Gd 0,306 2,35 1,57 1,47 1,75 2,01 1,2 2,53 2,08 159Tb 0,058 0,359 0,217 0,243 0,345 0,324 0,262 0,47 0,368 163Dy 0,381 2,38 1,57 1,59 2,16 2,99 1,65 3,59 2,8 165Ho 0,0851 0,67 0,323 0,367 0,42 0,615 0,429 0,619 0,61 166Er 0,249 1,89 1,05 1,23 1,4 1,95 1,3 2,26 1,65 169Tm 0,0356 0,242 0,173 0,176 0,228 0,343 0,201 0,408 0,286 172Yb 0,248 1,76 1,37 1,35 1,76 2,32 1,73 2,98 2,46 175Lu 0,0381 0,326 0,221 0,267 0,279 0,387 0,285 0,423 0,335 178Hf 0,179 2,02 1,17 1,29 1,7 2,03 1,7 2,48 1,78 181Ta 0,026 0,72 0,512 0,706 0,749 0,97 0,714 1,15 0,89 208Pb 3,65 24,32 16,29 20,49 28,15 26,55 20,76 36,8 24,36 232Th 0,0425 16,77 10,93 11,85 15,38 17,65 14,07 21,99 16,71 238U 0,0122 3,18 2,1 2,63 3,32 3,28 2,45 5,31 3,7 REE Chondrite normalised Tej_1 Tej_2 Tej_3 Tej_4 Tej_5 Tej_6 Tej_7 Tej_8 La 0,367 46,9210 30,7902 34,7411 51,1717 50,0272 47,6294 55,9401 39,5095 Ce 0,957 35,0052 23,0721 28,1818 42,0481 38,0669 34,0230 45,3710 30,9404 Pr 0,137 21,2409 15,7664 18,7591 25,4015 27,5912 23,6496 29,7080 21,7518 Nd 0,711 15,8087 10,6329 13,3052 14,9086 18,7060 14,0084 20,0703 16,0759 Sm 0,231 7,5325 6,5801 8,0952 12,0346 11,6017 8,6580 10,5628 8,1385 Eu 0,087 1,2069 1,8506 1,9425 3,4713 2,9310 3,5747 2,8736 2,8736 Gd 0,306 7,6797 5,1307 4,8039 5,7190 6,5686 3,9216 8,2680 6,7974 Tb 0,058 6,1897 3,7414 4,1897 5,9483 5,5862 4,5172 8,1034 6,3448 Dy 0,381 6,2467 4,1207 4,1732 5,6693 7,8478 4,3307 9,4226 7,3491 Ho 0,0851 7,8731 3,7955 4,3126 4,9354 7,2268 5,0411 7,2738 7,1680 Er 0,249 7,5904 4,2169 4,9398 5,6225 7,8313 5,2209 9,0763 6,6265 Tm 0,0356 6,7978 4,8596 4,9438 6,4045 9,6348 5,6461 11,4607 8,0337 Yb 0,248 7,0968 5,5242 5,4435 7,0968 9,3548 6,9758 12,0161 9,9194 Lu 0,0381 8,5564 5,8005 7,0079 7,3228 10,1575 7,4803 11,1024 8,7927 172 Element Chondrite Tej_9 Tej_10 9Be 0,04 1,49 <2.43 24Mg 143000 0,051 0,051 27Al 12900 40549,58 58745,41 30Si 160000 173580,42 283988 43Ca 13500 2055,74 3996,71 45Sc 8,64 2,12 2,33 51V 85 <1.18 1,08 60Ni 16500 0,61 0,26 85Rb 3,45 132,6 206,12 88Sr 11,9 23,92 34,81 89Y 2,25 12,68 17,46 90Zr 5,54 42,01 42,85 93Nb 0,375 6,86 9,97 137Ba 3,41 220,26 351,7 139La 0,367 14,61 20,33 140Ce 0,957 27,2 41,39 141Pr 0,137 2,41 3,74 143Nd 0,711 9,86 12,6 147Sm 0,231 1,71 2,43 153Eu 0,087 0,225 0,289 157Gd 0,306 1,57 1,94 159Tb 0,058 0,292 0,368 163Dy 0,381 2,04 3,07 165Ho 0,0851 0,586 0,62 166Er 0,249 1,37 1,73 169Tm 0,0356 0,283 0,307 172Yb 0,248 1,74 2,4 175Lu 0,0381 0,274 0,388 178Hf 0,179 1,74 2,19 181Ta 0,026 0,624 0,998 208Pb 3,65 18,52 30,08 232Th 0,0425 14,44 19,05 238U 0,0122 2,54 4,1 REE Chondrite normalised Tej_9 Tej_10 La 0,367 39,8093 55,3951 Ce 0,957 28,4222 43,2497 Pr 0,137 17,5912 27,2993 Nd 0,711 13,8678 17,7215 Sm 0,231 7,4026 10,5195 Eu 0,087 2,5862 3,3218 Gd 0,306 5,1307 6,3399 Tb 0,058 5,0345 6,3448 Dy 0,381 5,3543 8,0577 Ho 0,0851 6,8860 7,2855 Er 0,249 5,5020 6,9478 Tm 0,0356 7,9494 8,6236 Yb 0,248 7,0161 9,6774 Lu 0,0381 7,1916 10,1837 173 Element Chondrite KgL2-5_1 KgL2-5_2 KgL2-5_3 KgL2-5_4 KgL2-5_5 KgL2-5_6 KgL2-5_7 KgL2- 5_8 9Be 0,04 2,77 3,12 <2.79 1,5 1,78 1,15 <3.43 0,78 24Mg 143000 0,067 0,067 0,067 0,067 0,067 0,067 0,067 0,067 27Al 12900 80680,3 84212,85 100388,49 79042,34 79289,84 101215,55 97857,91 72096,44 30Si 160000 367750,06 355564,63 484838 389444,28 386748,25 436103,81 446147,03 362046 43Ca 13500 5447,01 6029,38 6587,61 6387,58 6012,29 5923,1 6465,04 5488,47 45Sc 8,64 3,64 3,99 6,66 4,03 4,51 4,62 4,88 4,14 51V 85 1,03 <0.70 1,08 0,87 1,16 <0.97 1,2 1,61 60Ni 16500 0,34 1,27 0,75 <0.26 <0.80 <0.73 0,87 <0.45 85Rb 3,45 300,99 284,88 493,48 297,43 314,13 365,21 457,52 269,27 88Sr 11,9 47,28 40,91 18,6 47,83 41,33 45,08 24,38 47,36 89Y 2,25 24,58 28,25 45,82 24,43 24,53 36,79 48,66 20,35 90Zr 5,54 74,17 83,82 87,69 71,22 65,23 99,16 85,04 74,67 93Nb 0,375 15,53 14,77 25,46 15,63 16,26 18,17 23,17 13,65 137Ba 3,41 520,78 485,74 69,65 562,21 467,79 316,93 78,15 663,2 139La 0,367 26,64 27,75 26,94 28,66 25,57 30,53 27,34 29,11 140Ce 0,957 60,21 57,79 67,19 62,69 60,68 61,45 61,07 62,06 141Pr 0,137 5,75 5,8 6,96 5,87 5,73 6,25 6,29 5,69 143Nd 0,711 19,41 19,35 25,47 19,92 17,29 21,56 23,03 18,03 147Sm 0,231 3,69 3,91 6,04 3,71 3,41 4,77 4,81 3,64 153Eu 0,087 0,531 0,388 0,282 0,467 0,434 0,462 0,273 0,405 157Gd 0,306 3,46 3,92 5,57 3,46 2,65 4,56 6,25 2,61 159Tb 0,058 0,662 0,765 1,22 0,584 0,613 0,738 0,96 0,635 163Dy 0,381 3,83 4,27 7,42 3,81 3,46 5,52 6,72 3,47 165Ho 0,0851 0,819 0,98 1,63 0,806 0,955 1,27 1,53 0,592 166Er 0,249 2,52 2,77 5,09 2,52 2,55 3,66 4,91 2,07 169Tm 0,0356 0,464 0,535 0,796 0,397 0,445 0,656 0,676 0,385 172Yb 0,248 3,39 3,48 5,86 3,42 3,12 4,89 6,4 2,53 175Lu 0,0381 0,523 0,574 0,977 0,454 0,569 0,771 0,94 0,437 178Hf 0,179 2,7 3,24 4,05 3,14 2,73 3,97 3,72 2,8 181Ta 0,026 1,5 1,38 2,92 1,47 1,53 1,98 2,48 1,42 208Pb 3,65 45,01 42,21 69,28 44,25 48,18 51,28 63,22 44,68 232Th 0,0425 24,95 26,35 44,81 26,63 26,2 37,37 44,4 23,61 238U 0,0122 5,56 5,52 12,08 5,79 6,3 7,8 10,04 5,25 REE Chondrite normalised KgL2-5_1 KgL2-5_2 KgL2-5_3 KgL2-5_4 KgL2-5_5 KgL2-5_6 KgL2-5_7 KgL2- 5_8 La 0,367 72,5886 75,6131 73,4060 78,0926 69,6730 83,1880 74,4959 79,3188 Ce 0,957 62,9154 60,3866 70,2090 65,5068 63,4065 64,2111 63,8140 64,8485 Pr 0,137 41,9708 42,3358 50,8029 42,8467 41,8248 45,6204 45,9124 41,5328 Nd 0,711 27,2996 27,2152 35,8228 28,0169 24,3179 30,3235 32,3910 25,3586 Sm 0,231 15,9740 16,9264 26,1472 16,0606 14,7619 20,6494 20,8225 15,7576 Eu 0,087 6,1034 4,4598 3,2414 5,3678 4,9885 5,3103 3,1379 4,6552 Gd 0,306 11,3072 12,8105 18,2026 11,3072 8,6601 14,9020 20,4248 8,5294 Tb 0,058 11,4138 13,1897 21,0345 10,0690 10,5690 12,7241 16,5517 10,9483 Dy 0,381 10,0525 11,2073 19,4751 10,0000 9,0814 14,4882 17,6378 9,1076 Ho 0,0851 9,6240 11,5159 19,1539 9,4712 11,2221 14,9236 17,9788 6,9565 Er 0,249 10,1205 11,1245 20,4418 10,1205 10,2410 14,6988 19,7189 8,3133 Tm 0,0356 13,0337 15,0281 22,3596 11,1517 12,5000 18,4270 18,9888 10,8146 Yb 0,248 13,6694 14,0323 23,6290 13,7903 12,5806 19,7177 25,8065 10,2016 Lu 0,0381 13,7270 15,0656 25,6430 11,9160 14,9344 20,2362 24,6719 11,4698 174 Element Chondrite KgL2-5_9 KgL2-5_10 9Be 0,04 5,88 7,15 24Mg 143000 0,067 0,067 27Al 12900 85221,43 85646,46 30Si 160000 471674,88 488406,75 43Ca 13500 7026,11 5638,62 45Sc 8,64 5,14 5,31 51V 85 1,43 0,91 60Ni 16500 <0.74 1,17 85Rb 3,45 377,78 443,02 88Sr 11,9 38,51 21,02 89Y 2,25 30,76 37,12 90Zr 5,54 78,46 76,79 93Nb 0,375 17,89 22,55 137Ba 3,41 327,62 78,65 139La 0,367 26,12 23,49 140Ce 0,957 62,45 58,24 141Pr 0,137 5,8 5,61 143Nd 0,711 19,58 20,49 147Sm 0,231 4,27 5,04 153Eu 0,087 0,316 0,317 157Gd 0,306 3,78 4,75 159Tb 0,058 0,722 0,57 163Dy 0,381 4,09 5,9 165Ho 0,0851 0,94 1,36 166Er 0,249 2,91 3,56 169Tm 0,0356 0,458 0,649 172Yb 0,248 3,79 5,14 175Lu 0,0381 0,606 0,843 178Hf 0,179 2,9 2,97 181Ta 0,026 1,93 2,4 208Pb 3,65 54,15 59,32 232Th 0,0425 31,68 38,84 238U 0,0122 7,73 10,63 REE Chondrite normalised KgL2-5_9 KgL2-5_10 La 0,367 71,1717 64,0054 Ce 0,957 65,2560 60,8568 Pr 0,137 42,3358 40,9489 Nd 0,711 27,5387 28,8186 Sm 0,231 18,4848 21,8182 Eu 0,087 3,6322 3,6437 Gd 0,306 12,3529 15,5229 Tb 0,058 12,4483 9,8276 Dy 0,381 10,7349 15,4856 Ho 0,0851 11,0458 15,9812 Er 0,249 11,6867 14,2972 Tm 0,0356 12,8652 18,2303 Yb 0,248 15,2823 20,7258 Lu 0,0381 15,9055 22,1260 175 9. 3 Major components internal standards and calibration (EPMA) Signal(s) Used : Na Ka, Si Ka, K Ka, Ca Ka, Ti Ka, Fe Ka, Al Ka, Mg Ka, P Ka, Ba La, Ce La, Cr Ka, Mn Ka, Sr La, Rb La Spectromers Conditions : Sp1 LTAP, Sp2 TAP, Sp3 LPET, Sp3 LPET, Sp3 LPET, Sp5 LIF, Sp2 TAP, Sp4 TAP, Sp3 LPET, Sp5 LIF, Sp5 LIF, Sp5 LIF, Sp5 LIF, Sp3 LPET, Sp3 LPET Full Spectromers Conditions : Sp1 LTAP(2d= 0,K= 0), Sp2 TAP(2d= 0,K= 0), Sp3 LPET(2d= 0,K= 0), Sp3 LPET(2d= 0,K= 0), Sp3 LPET(2d= 0,K= 0), Sp5 LIF(2d= 0,K= 0), Sp2 TAP(2d= 0,K= 0), Sp4 TAP(2d= 0,K= 0), Sp3 LPET(2d= 0,K= 0), Sp5 LIF(2d= 0,K= 0), Sp5 LIF(2d= 0,K= 0), Sp5 LIF(2d= 0,K= 0), Sp5 LIF(2d= 0,K= 0), Sp3 LPET(2d= 0,K= 0), Sp3 LPET(2d= 0,K= 0) Column Conditions : Cond 1 : 15keV 2nA , Cond 2 : 15keV 10nA Cond 1 : Na Ka, Si Ka, K Ka, Ca Ka, Ti Ka, Fe Ka, Al Ka, Mg Ka Cond 2 : P Ka, Ba La, Ce La, Cr Ka, Mn Ka, Sr La, Rb La Date : 1-Sep-2010 User Name : sx Setup Name : EGatti_Glass_Aug_2010.qtiSet DataSet Comment : 1 Comment : Analysis Date : 31/08/2010 19:37:02 Project Name : Emma Gatti Sample Name : 27_Aug_2010 Pha Parameters : Bias Gain Dtime Blin Wind Mode Sp1(Na Ka) 1300 2639 3 560 768 Inte Sp2(Si Ka) 1308 2714 3 560 1404 Inte Sp3(K Ka) 1850 895 3 560 791 Inte Sp3(Ca Ka) 1850 895 3 560 791 Inte Sp3(Ti Ka) 1850 895 3 560 791 Inte Sp5(Fe Ka) 1859 425 3 560 738 Inte Sp2(Al Ka) 1308 2714 3 560 1404 Inte Sp4(Mg Ka) 1317 2819 3 560 4960 Inte Sp3(P Ka) 1850 895 3 560 791 Inte Sp5(Ba La) 1859 425 3 560 738 Inte Sp5(Ce La) 1859 425 3 560 738 Inte Sp5(Cr Ka) 1859 425 3 560 738 Inte Sp5(Mn Ka) 1859 425 3 560 738 Inte Sp3(Sr La) 1850 895 3 560 791 Inte Sp3(Rb La) 1850 895 3 560 791 Inte Peak Position : Sp1 46379 (-600, 400), Sp2 27737 (-500, 500), Sp3 42751 (-300, 250), Sp3 38393 (-300, 250), Sp3 31437 (-350, 250), Sp5 48088 (-250, 300), Sp2 32460 (-500, 500), Sp4 38521 (-500, 500), Sp3 70286 (-700, 600), Sp5 68937 (-500, 500), Sp5 63617 (-200, 350), Sp5 56870 (-250, 300), Sp5 52205 (200, 1.0221), Sp3 78354 (-300, 300), Sp3 83565 (1) Current Sample Position : X = -13171 Y = 3888 Z = -100 Standard Name : Na On Jad Si On Si Glass K On KSp Ca On Diopside Ti On Rutile Fe On Fayalite Al On Cor Mg On Periclase P On Apatite Ba On Benitoite Ce On CeAl2 Cr On Cr Mn On Mn 176 Sr On Celest Rb On Rb Glass Standard composition : Jad = O : 47.5%, Na : 11.3%, Al : 13.2%, Si : 27.8%, Fe : 0.2% Si Glass = O : 48.0939%, F : 0.64%, Na : 4.2066%, Mg : 0.006%, Al : 5.5989%, Si : 34.8755%, K : 3.6358%, Ca : 0.1072%, Ti : 0.1079%, Mn : 0.0465%, Fe : 2.6817% KSp = O : 46.1%, Na : 0.8%, Al : 9.7%, Si : 30.3%, K : 12.8%, Fe : 0.3% Diopside = O : 44.5%, Mg : 11.2%, Si : 25.9%, Ca : 18.4% Rutile = Ti : 59.95%, O : 40.05% Fayalite = O : 31.405%, Si : 13.783%, Fe : 54.812% Cor = O : 47.1%, Al : 52.9% Periclase = O : 39.7%, Mg : 60.3% Apatite = O : 38.1%, F : 3.4%, P : 18.4%, Cl : 0.4%, Ca : 39.7% Benitoite = O : 34.8%, Si : 20.4%, Ti : 11.6%, Ba : 33.2% CeAl2 = Ce : 72.1959%, Al : 27.8041% Cr = Cr : 100.% Mn = Mn : 100.% Celest = O : 34.7%, S : 17.4%, Sr : 47.1%, Ba : 0.8% Rb Glass = O : 30.026%, Al : 7.165%, Ge : 37.544%, Rb : 9.52%, Ca : 15.745% Calibration file name : Na : Jad_Na192.calDat Si : Si Glass_Si041.calDat K : KSp_K143.calDat Ca : Diopside_Si_Ca195.calDat Ti : Rutile_Ti157.calDat Fe : Fayalite_Fe154.calDat Al : Cor_Al_Al041.calDat Mg : Periclase_Mg_Mg027.calDat P : Apatite_P048.calDat Ba : Benitoite_Ba_Ba019.calDat Ce : CeAl2_Ce008.calDat Cr : Cr_Cr163.calDat Mn : Mn_Mn168.calDat Sr : Celest_Sr063.calDat Rb : Rb Glass_Rb002.calDat Beam Size : 15, 15 µm 177 9.4 Major components geochemical analyses (EPMA) Element BTS3/1 BTS3/2 BTS3/3 BTS3/4 BTS3/5 BTS3/6 BTS3/7 BTS3/8 BTS3/9 BTS3/10 BTS3/11 BTS3/12 BTS3/13 BTS3/14 BTS3/15 Na2O 3,2311 2,9863 3,3368 3,1026 3,1638 3,2671 3,164 1,0906 3,1023 3,1876 2,5656 3,1166 2,8421 2,8866 3,1845 SiO2 75,8637 75,3822 75,3104 74,0233 75,1733 76,3076 75,6084 75,5874 74,8892 75,8842 70,7782 74,7481 74,524 74,1139 75,0771 K2O 5,0218 5,2068 5,0452 5,1835 5,0419 5,3076 5,2347 4,7513 5,1116 5,1404 5,3424 5,0314 5,2016 5,2943 5,0205 CaO 0,7654 0,7025 0,7261 0,7422 0,772 0,6885 0,694 0,7727 0,7368 0,7451 0,7705 0,763 0,7436 0,823 0,7701 TiO2 0,0447 0,0281 0,0735 0,0574 0,0426 0,0888 0,0109 0,0561 0,0009 0,0447 0,0595 -0,0112 0,0602 0,0641 0,0617 FeO 0,782 0,7819 0,7561 0,891 1,0766 0,8745 0,8651 0,8476 0,9766 0,8233 0,8902 1,1686 0,7924 0,6933 0,8259 Al2O3 11,8873 11,9673 11,97 12,1441 11,6576 12,0884 11,8914 12,1054 12,0392 11,9829 11,6293 11,8928 11,6765 11,7876 12,0797 MgO 0,059 0,0426 0,0359 0,0426 0,0921 0,0294 0,0721 0,1064 0,0197 0,0458 0,0753 0,0493 0,121 0,1015 0,0525 P2O5 -0,0031 0,0145 0,0237 0,0159 0,024 -0,0143 0,0122 0,0041 0,0183 0,0123 0,0006 0,0079 0,0031 0,0155 0,0005 BaO -0,0233 0,1183 0,0216 -0,0812 0,0859 -0,0216 0,0431 0,0817 0,1404 0,0108 0,1296 -0,0465 0 0,0973 0,1188 Ce2O3 -0,0556 0,0905 -0,0217 -0,0034 0,0575 -0,0409 -0,0996 -0,0595 0,0122 0,0275 0,0818 0,0042 0,0241 -0,0146 -0,009 Cr2O3 -0,0172 0,0149 0,052 0,0013 0,0356 -0,0189 0,0193 -0,017 0,0402 0,0216 -0,0203 -0,0258 -0,0124 0,039 -0,0275 MnO 0,0415 0,0706 -0,0014 -0,0115 0,0954 0,0478 0,1091 0,0476 0,0708 0,0849 0,0755 0,0564 0,0521 0,0867 0,051 SrO -0,051 -0,0249 -0,046 -0,0311 -0,017 -0,0316 -0,0197 -0,024 -0,0368 -0,0565 -0,05 -0,0156 -0,0381 -0,0644 0,0013 Rb2O -0,9446 -0,9205 -0,9586 -0,9147 -0,9647 -0,907 -0,8991 -0,9009 -0,9169 -0,9297 -0,9397 -0,8834 -0,9519 -0,9348 -0,9294 Total 97,6965 97,4064 97,3515 96,2039 97,3183 98,6997 97,7242 95,4509 97,1581 98,0112 92,3986 96,8385 96,0407 96,0028 97,2434 Eleme nt BTS12 / 1 BTS12 / 2 BTS12 / 3 BTS12 / 4 BTS12 / 5 BTS12 / 6 BTS12 / 7 BTS12 / 8 BTS12 / 9 BTS12 / 10 BTS12 / 11 BTS12 / 12 BTS12 / 13 BTS12 / 14 BTS12 / 15 BTS12 / 16 Na2O 2,9595 3,2161 2,7794 2,949 2,9592 3,0927 2,4223 2,8791 2,9968 2,4588 2,6868 3,1005 3,1139 3,2333 3,0466 1,7819 SiO2 74,262 3 75,343 6 72,387 1 75,214 8 76,056 5 75,815 6 69,491 4 74,988 2 76,216 3 70,4214 75,241 74,6326 75,3382 75,0356 75,4749 76,1617 K2O 5,0745 5,3158 4,6541 5,3028 5,1146 5,3089 5,059 5,2582 5,0141 4,8423 5,1748 5,121 4,8928 5,2517 5,2511 4,9203 CaO 0,8391 0,5805 0,6765 0,8122 0,7999 0,8523 0,6154 0,76 0,6441 0,797 0,8019 0,8016 0,8165 0,7927 0,8044 0,8157 TiO2 0,0048 0,0356 0,0045 0,0407 0,0347 0,0559 0,0909 0,0199 0,0417 0,028 0,0314 0,0563 0,0322 0,0382 0,0488 0,0229 FeO 0,9987 0,4278 1,0449 0,7689 0,9779 0,7693 0,5211 0,782 0,6112 0,8234 0,7603 1,0141 0,7984 0,8919 0,8982 0,8322 Al2O3 12,140 4 11,430 7 12,007 11,890 3 12,075 3 11,800 2 10,958 8 12,116 3 11,783 5 11,4521 11,5864 11,9568 12,2165 12,0503 11,6542 11,9664 MgO 0,0163 0,0163 0,0033 0,0783 0,144 0,0098 0,1042 0,0229 0,0359 0,1172 0,0587 0,0164 0,0653 0,1175 0,0065 0,0486 P2O5 0,0038 0,0017 -0,004 0,0124 0,0242 -0,0009 0,0149 0,0131 0,0087 0,0033 0,0034 0,0188 0,0083 0,0094 0,0009 0,0034 BaO 0,0971 -0,0216 0,043 0,0466 0,1186 0,0433 -0,0216 0,1514 0,0753 -0,1294 -0,0648 0,0216 -0,0215 0,0539 0,1402 -0,108 Ce2O3 0,0035 0,0287 0,0814 -0,0916 0,0569 0,0071 -0,0641 0,0882 0,0615 -0,0298 0,0051 0,0251 0,049 -0,0404 0,0719 -0,0597 Cr2O3 0,023 0,0096 0,0232 -0,0024 0,0113 -0,0356 0,012 0,0047 -0,0027 -0,057 -0,0365 -0,0098 -0,0115 0,001 0,0524 0,0083 MnO 0,107 0,0772 0,052 0,1056 0,03 0,0976 0,0619 0,0167 0,1604 0,1236 0,0755 0,096 0,089 0,0575 -0,0157 0,0155 SrO 0,0066 -0,0183 -0,0459 -0,0411 -0,0538 -0,046 -0,0144 -0,0132 -0,0131 -0,0197 -0,0026 -0,0223 -0,0563 -0,0236 -0,0249 -0,0406 Rb2O -0,9352 -0,9454 -0,9365 -0,9103 -0,9485 -0,9073 -0,8932 -0,9286 -0,9279 -0,9486 -0,935 -0,9504 -0,9831 -0,9421 -0,8995 -0,9112 Total 96,536 6 96,483 6 93,756 3 97,221 6 98,403 97,852 6 89,351 8 97,100 7 97,649 4 91,0673 96,4253 96,8608 97,42 97,533 97,4501 96,5768 178 Elemen t KgL2 / 1 KgL2 / 2 KgL2 / 3 KgL2 / 4 KgL2 / 5 KgL2 / 6 KgL2 / 7 KgL2 / 8 KgL2 / 9 KgL2 / 10 KgL2 / 11 KgL2 / 12 KgL2 / 13 KgL2 / 14 KgL2 / 15 Na2O 3,0144 -0,011 3,106 2,9365 2,9455 2,8436 2,8787 3,2091 0,0172 3,0905 1,7883 2,4937 2,076 2,8114 3,3323 SiO2 74,6995 104,316 5 74,8619 73,8986 74,0989 74,6158 72,0656 75,8888 104,085 5 75,4812 75,2938 69,0309 74,8564 75,456 74,3874 K2O 4,964 -0,0316 4,8395 5,2984 5,3508 5,0862 4,8845 5,1458 -0,0083 4,9594 5,1649 4,5173 5,2206 5,5016 5,0396 CaO 0,6839 -0,0394 0,7178 0,7846 0,7975 0,6294 0,7234 0,7639 -0,0045 0,7736 0,7214 0,7244 0,7355 0,7466 0,6565 TiO2 0,0304 0,0194 0,0765 0,0912 0,0933 0,115 0,0729 0,0475 0,007 0,0783 0,0615 0,0522 0,0551 0,0551 0,0647 FeO 0,7865 0,0511 0,9111 0,667 0,8879 0,9837 0,7308 0,7083 0,0642 0,7474 0,8966 1,0211 0,6974 0,6714 0,7002 Al2O3 12,1543 0,0201 12,1311 12,0602 12,2283 11,8781 11,1822 12,1527 0,0779 11,6764 11,8135 12,1312 12,1045 12,0688 12,1373 MgO 0,0751 0,0096 0,1079 0,0293 0,1337 0,0195 0,0619 0,0815 0,0159 0,0913 0,0419 0,0358 0,0712 0,078 0,0457 P2O5 0,0046 0,0066 0,0083 0,0017 0,006 -0,0009 0,0005 -0,0107 0,017 0,0039 -0,0047 0,0702 0,0179 -0,0038 -0,0162 BaO 0,1181 -0,0216 -0,129 0,0645 -0,0115 0,043 0,1075 -0,0323 -0,0757 0,0107 -0,0116 0,0232 0,1516 -0,0108 -0,2093 Ce2O3 0,1314 -0,0639 -0,1002 -0,0047 0,0325 0,0047 0,0023 0,0878 -0,0631 -0,0246 0,0474 -0,0494 0,02 -0,0262 -0,0025 Cr2O3 -0,0302 0,0099 -0,002 0,0144 0,006 -0,0017 -0,002 -0,021 -0,0074 0,0141 -0,0066 0,0037 0,0244 0,0064 -0,024 MnO 0,0766 -0,0288 0,0231 0,0252 0,107 0,0926 0,0045 0,0727 0,0307 0,0407 0,133 0,0838 0,1164 0,1002 0,0625 SrO -0,0628 -0,0646 -0,0105 -0,0222 -0,0293 -0,0497 -0,017 -0,0236 -0,0074 -0,0587 -0,0818 0,0057 -0,0552 -0,0131 -0,0681 Rb2O -0,9364 -0,9132 -0,9155 -0,9805 -0,9419 -0,9112 -0,9248 -0,9263 -0,8873 -0,9513 -0,9508 -0,9384 -0,9487 -0,9405 -0,9186 Total 96,739 104,433 2 96,7832 95,8715 96,6874 96,3117 92,7148 98,1581 104,315 2 96,9676 95,9622 90,1932 96,147 97,4955 96,4263 Elem ent KgL2- 12 / 1 KgL2- 12 / 2 KgL2- 12 / 3 KgL2- 12 / 4 KgL2- 12 / 5 KgL2- 12 / 6 KgL2- 12 / 7 KgL2- 12 / 8 KgL2- 12 / 9 KgL2- 12 / 10 KgL2- 12 / 11 KgL2- 12 / 12 KgL2- 12 / 13 KgL2- 12 / 14 KgL2- 12 / 15 KgL2- 12 / 16 KgL2- 12 / 17 Na2O 0,0266 3,1274 2,8511 3,3396 - 0,0272 - 0,0185 3,1477 3,0638 3,0034 3,157 7,1821 3,3342 6,9711 3,1283 3,1687 3,0217 6,1919 SiO2 102,98 73 74,432 3 66,779 9 75,496 7 102,06 33 103,10 73 74 75,708 2 75,223 1 74,4551 61,581 75,0114 61,2343 74,4908 74,5508 72,8272 57,9962 K2O - 0,0211 4,963 12,829 1 4,996 0,0108 - 0,0088 5,1552 5,0735 4,9625 4,8804 0,8185 5,108 0,8093 5,0976 5,0139 5,0643 0,6171 CaO 0,0407 0,7941 0,1994 0,6475 0,004 - 0,0133 0,7736 0,6973 0,7871 0,6637 6,4462 0,6846 7,3245 0,7863 0,8125 0,8479 8,7435 TiO2 0,0118 0,0508 -0,034 0,037 - 0,0054 - 0,0076 0,0644 - 0,0012 - 0,0148 0,0488 -0,0036 0,0331 0,0006 0,0473 0,0783 0,018 0,012 FeO -0,054 1,0592 0,1628 0,594 - 0,1225 0,0496 0,8378 0,8464 1,0042 0,8845 0,2512 1,072 -0,0101 0,7091 0,9278 0,7192 0,1877 Al2O3 0,1608 12,101 6 18,735 1 11,936 4 0,0427 0,0276 11,697 7 11,501 5 11,858 1 11,7271 25,1319 11,9339 25,2803 12,0512 11,6975 11,7797 26,1199 MgO 0,0032 0,0784 - 0,0227 0,0749 0,0478 - 0,0064 0,0588 0,0555 0,0457 0,062 -0,0133 0,0688 0,01 0,0719 0,0884 0,0748 0,0233 P2O5 - 0,0219 0,0132 0,0033 0,0144 0,0146 0,0119 0,0136 0,0102 0,0171 0,0108 -0,0124 -0,0006 0,0173 -0,0024 0,0044 0,0014 0,0155 BaO 0 -0,043 0,3014 0,0537 - 0,0324 - 0,0117 0,0323 - 0,0431 0,043 0 -0,0465 0,043 0,0323 0,2475 0,1931 -0,0117 0,1184 Ce2O 3 -0,002 - 0,0739 0,0278 - 0,0697 0,0386 0,0718 0,0518 - 0,0185 0 0,0078 -0,0754 -0,0685 0,0352 -0,0313 -0,0187 -0,0493 0,0411 Cr2O3 0,0007 0,0066 0,063 - 0,0051 - 0,0271 - 0,0305 - 0,0345 - 0,0115 - 0,0098 0,0056 -0,0132 -0,0012 -0,0007 0,0452 -0,0056 -0,049 -0,0171 MnO - 0,0241 0,145 - 0,0059 0,0981 0,0246 0,004 0,0323 0,0638 0,0595 0,075 -0,0252 0,0452 -0,0241 0,096 0,0752 0,0377 0,0344 SrO 0,0199 - 0,0564 -0,012 - 0,0562 - 0,0124 - 0,0135 - 0,0603 - 0,0262 0,0196 -0,0353 0,063 -0,0406 0,0028 -0,042 -0,0026 -0,0384 0,0334 Rb2O - 0,8999 -0,91 - 0,9445 -0,928 - 0,8922 - 0,8669 - 0,9128 - 0,9005 -0,945 -0,8976 -1,015 -0,9304 -1,0495 -0,9623 -0,9268 -0,9738 -1,0464 Total 103,25 1 96,771 6 101,95 27 97,288 3 102,24 63 103,27 22 95,865 2 97,020 2 97,023 4 95,9779 101,473 9 97,3343 101,717 7 96,7712 96,6104 94,392 100,134 3 179 Elemen t KgL3 / 1 KgL3 / 2 KgL3 / 3 KgL3 / 4 KgL3 / 5 KgL3 / 6 KgL3 / 7 KgL3 / 8 KgL3 / 9 KgL3 / 10 KgL3 / 11 KgL3 / 12 KgL3 / 13 KgL3 / 14 KgL3 / 15 Na2O 3,0931 3,1816 2,8463 2,8745 3,334 2,8049 2,9772 2,9264 6,9281 3,1077 6,2449 3,1626 2,869 3,1981 3,1366 SiO2 74,3512 75,3082 74,0219 74,1072 74,9952 71,0294 74,3738 73,0762 60,6906 73,9671 58,3207 74,4527 73,99 74,2981 74,9078 K2O 4,9559 5,1427 5,0404 5,2382 4,8904 4,8178 5,1453 4,9418 0,7933 4,9282 0,527 5,2088 5,5485 5,0254 5,0376 CaO 0,8559 0,8664 0,6097 0,8577 0,6677 0,6377 0,7441 0,6835 7,2002 0,828 8,5492 0,8178 0,8537 0,8269 0,8474 TiO2 -0,0024 0,0172 0,0638 0,0395 0,0755 0,0574 0,1016 0,0698 -0,0192 0,0428 -0,0042 0,0704 0,0469 0,0274 0,0992 FeO 0,6088 0,6354 0,8899 0,9427 0,8337 0,8732 0,7492 1,0518 0,1458 0,763 -0,1227 1,0545 0,8729 0,6221 0,8703 Al2O3 11,7288 11,7221 11,6995 11,9541 11,8165 11,5387 11,7475 12,0421 25,1787 11,9132 26,6745 12,1533 11,7718 11,8896 11,8579 MgO 0,0359 0,0065 0,0685 0,0785 0,0327 0,0685 0,0522 0,0914 -0,0133 0,1012 0,0597 0,0523 0,1173 0,0815 0,0359 P2O5 0,0064 0,0028 0,0307 -0,0044 -0,0185 0,0135 0,0182 0,0211 0,0153 -0,0062 0,0112 -0,0078 0,0029 0,0142 -0,0024 BaO -0,0215 0,2045 -0,07 -0,0968 0,1176 0,0862 0,0538 -0,0431 -0,0108 0,1076 0,0815 -0,1397 0,1292 0,0699 0,1513 Ce2O3 0,0059 -0,0662 0,0319 0,0458 0,0249 -0,1048 -0,0302 -0,0059 -0,0259 0,0263 0,0191 -0,0246 0,0506 -0,0085 0,0072 Cr2O3 -0,0452 -0,0907 -0,0223 0,0708 -0,0515 -0,0113 0,0039 0,0081 -0,0024 0,0284 -0,0515 -0,0063 0,0005 -0,0161 0,0391 MnO 0,0553 0,0097 0,0766 0,0278 0,054 0,0298 0,0498 0,0974 0,0097 0,0391 -0,0081 0,0588 0,057 -0,0068 0,0619 SrO -0,0432 -0,0196 -0,0426 -0,0183 -0,013 -0,0013 -0,0301 -0,0407 0,0278 -0,0026 0,0557 0,0524 -0,0419 -0,0142 -0,0553 Rb2O -0,9566 -0,9341 -0,9614 -0,921 -0,905 -0,8965 -0,9478 -0,9464 -1,0401 -0,9408 -1,0609 -0,9277 -0,9323 -0,9054 -0,9054 Total 95,6972 97,097 95,379 96,2367 96,8422 91,9571 96,0167 95,0096 100,989 4 95,8524 100,5434 97,0837 96,3103 96,053 97,0522 Elem ent JWP3- 11/ 1 JWP3- 11/ 2 JWP3- 11/ 3 JWP3- 11/ 4 JWP3- 11/ 5 JWP3- 11/ 6 JWP3- 11/ 7 JWP3- 11/ 8 JWP3- 11/ 9 JWP3- 11/ 10 JWP3- 11/ 11 JWP3- 11/ 12 JWP3- 11/ 13 JWP3- 11/ 14 JWP3- 11/ 15 Na2O 3.1450 2.9693 3.5437 2.9948 3.1774 3.1481 3.2042 3.0844 3.1765 3.0695 3.5776 3.3210 3.4282 3.3097 3.3100 SiO2 74.3881 68.6847 76.1958 73.7225 72.8102 74.7037 74.6102 74.3000 75.0125 73.9902 75.2083 75.5354 74.9034 73.6822 75.8691 K2O 5.0654 4.3871 4.8344 4.9081 4.4234 4.8722 5.1489 5.1581 5.0309 4.9899 4.9717 5.0110 5.1358 4.6917 4.8903 CaO 0.6567 0.6618 0.6873 0.6205 0.7217 0.7389 0.7638 0.8152 0.5726 0.8194 0.6741 0.6391 0.7452 0.6412 0.6645 TiO2 0.0614 0.0202 0.0475 0.0536 0.0409 0.0710 0.0652 0.0445 0.0078 0.0755 0.0523 0.0334 0.0637 0.0628 0.0430 FeO 1.0176 0.6867 1.0889 0.7510 1.0932 0.6727 1.0224 0.8049 0.9537 0.7349 0.8898 0.6671 1.0182 0.4273 0.7971 Al2O3 12.0689 10.4998 12.1337 11.6378 11.4742 11.6355 11.9931 11.9119 11.8631 11.8112 12.3454 11.7023 11.6585 11.6587 11.8368 MgO 0.0654 0.0686 0.0688 -0.0065 0.0687 0.0425 0.0720 0.0195 0.0620 -0.0228 0.0393 0.0750 0.0491 0.0650 0.0588 P2O5 0.0172 0.0066 -0.0048 -0.0069 0.0082 0.0100 -0.0107 -0.0083 -0.0092 0.0156 0.0135 0.0160 0.0070 0.0129 0.0119 BaO -0.0801 0.0466 0.0645 0.0580 -0.0967 0.2084 0.1166 0.0466 -0.0348 -0.0700 0.1719 0.0465 -0.0696 -0.0108 0.0116 Ce2O3 -0.0108 0.0365 0.0231 0.0008 -0.0454 0.0936 -0.1023 0.0267 0.0207 0.0909 0.0313 -0.0381 0.0232 0.0035 -0.0466 Cr2O3 -0.0605 0.0204 -0.0098 0.0595 -0.0200 0.0187 0.0037 -0.0132 0.0174 -0.0061 0.0249 -0.0074 0.0029 -0.0142 0.0587 MnO 0.0990 0.0495 0.0906 0.0471 0.0999 0.1283 0.0475 -0.0168 0.0496 0.0501 0.1040 0.0616 0.0639 0.1160 0.1430 SrO -0.0223 -0.0454 -0.0511 -0.0663 -0.0210 -0.0338 -0.0469 0.0284 -0.0480 -0.0596 -0.0079 -0.0821 -0.0325 -0.0196 -0.0340 Rb2O -0.9347 -0.9401 -0.9277 -0.8919 -0.9221 -0.9331 -0.9101 -0.9449 -0.9289 -0.9470 -0.9308 -0.9464 -0.9062 -0.9381 -0.9395 Total 96.5847 88.1378 98.7783 94.8536 93.9178 96.3435 97.0475 96.2403 96.7667 95.6471 98.1041 97.1084 97.0989 94.6709 97.6948 180 Element BR6/1 BR6/2 BR6/3 BR6/4 BR6/5 BR6/6 BR6/7 BR6/8 BR6/9 BR6/10 BR6/11 BR6/12 BR6/13 BR6/14 BR6/15 Na2O 3.3748 3.4115 6.9127 3.2768 3.1516 3.0402 3.1513 2.5310 3.1368 1.9732 3.3450 3.0170 3.0219 3.0630 2.1424 SiO2 74.3727 74.2062 60.7375 72.4466 74.2833 74.5214 73.7132 62.1390 72.7587 52.3446 74.8098 74.3737 73.6881 75.7562 61.2427 K2O 4.6454 4.8378 0.7039 4.9141 4.9452 5.2556 4.9905 3.8022 4.6227 2.9128 5.0076 5.3659 4.6613 5.0367 4.6938 CaO 0.7538 0.5794 7.5325 0.5835 0.8211 0.7166 0.7624 0.6922 0.9163 0.5367 0.7799 0.8175 0.9492 0.8036 0.7034 TiO2 0.0099 0.0683 0.0096 0.0078 0.0180 0.0193 0.0539 0.0713 0.0852 0.0795 0.0487 0.0933 0.0830 0.0780 0.0500 FeO 1.0201 0.5385 0.2868 1.0443 0.9611 0.5657 0.8177 0.7826 1.0281 0.8871 0.8880 0.7638 1.0704 0.6012 0.6263 Al2O3 12.2077 11.7077 25.0997 11.6118 11.4961 11.5573 11.4352 10.1710 11.6178 8.9002 11.9765 11.6560 11.5193 11.9377 9.4809 MgO 0.0327 0.0327 -0.0100 0.0327 0.0653 0.0456 0.1273 0.1370 0.0885 0.1925 0.0196 0.0750 0.1047 0.0424 0.0423 P2O5 0.0066 0.0096 0.0094 -0.0059 0.0048 -0.0076 0.0016 0.0167 0.0081 0.0350 0.0271 0.0105 0.0264 -0.0008 0.0182 BaO 0.1612 -0.1291 -0.0350 -0.0322 -0.0233 0.0234 0.0645 0.0816 0.1750 0.1858 0.0752 -0.0215 0.2441 0.0862 -0.0108 Ce2O3 0.0313 0.0493 -0.0675 -0.0372 0.0671 -0.0396 0.0082 0.0008 -0.0140 -0.0169 -0.0434 -0.0905 0.0453 -0.0322 -0.0082 Cr2O3 0.0256 -0.0340 0.0357 0.0354 -0.0172 -0.0082 0.0110 -0.0214 -0.0228 0.0314 0.0591 0.0320 -0.0066 0.0497 0.0027 MnO 0.0452 0.0813 0.0284 0.1018 -0.0335 0.0446 0.0112 0.0747 0.0892 0.0845 0.0231 0.0459 0.0494 0.0703 0.1003 SrO -0.0144 -0.0039 0.0480 -0.0446 0.0128 -0.0326 0.0222 0.0298 0.0128 -0.0028 -0.0511 -0.0288 -0.0057 0.0026 -0.0183 Rb2O -0.9166 -0.9265 -10.205 -0.9097 -0.8853 -0.9656 -0.8849 -0.9872 -0.9254 -0.9757 -0.9305 -0.9179 -0.9578 -0.9072 -0.9279 Total 96.6872 95.5224 101.4042 94.0549 95.8265 95.7897 95.1703 80.5300 94.5392 68.1633 97.0596 96.2505 95.4630 97.5278 79.1030 Eleme nt MRB3 / 1 MRB3 / 2 MRB3 / 3 MRB3 / 4 MRB3 / 5 MRB3 / 6 MRB3 / 7 MRB3 / 8 MRB3 / 9 MRB3 / 10 MRB3 / 11 MRB3 / 12 MRB3 / 13 MRB3 / 14 MRB3 / 15 Na2O 3.2996 3.3163 2.9769 3.0157 3.2322 3.4709 3.0315 3.1725 2.9065 3.0956 3.1599 3.0808 3.1753 3.0326 3.3241 SiO2 74.6966 73.8381 73.0840 75.1957 72.4957 74.2346 74.8945 73.7287 70.6581 74.8748 73.9969 74.5918 71.8785 73.2037 73.8389 K2O 4.9556 5.0502 4.9905 5.0520 4.7596 4.5201 5.1032 5.0207 4.3616 5.0758 5.0005 5.2891 5.0497 5.1408 5.1875 CaO 0.8490 0.8205 0.8674 0.7876 0.7235 0.6595 0.7335 0.7394 0.7560 0.7550 0.6668 0.7473 0.7333 0.8318 0.6586 TiO2 0.0359 0.0365 0.0652 0.0159 0.0240 0.0713 0.0547 0.0879 0.0581 0.0537 0.0315 0.0632 0.0451 0.0096 0.0229 FeO 0.8840 0.6319 0.9414 0.8081 1.0666 0.6775 0.9178 0.6298 0.7891 0.7985 0.9853 0.7379 0.9694 0.8773 1.0348 Al2O3 12.3120 11.8440 11.8997 11.8994 11.4962 11.7453 11.5755 11.7696 11.1126 11.8871 11.9393 11.8108 11.5647 11.8319 11.6088 MgO 0.0982 0.0588 0.0982 0.0684 0.0720 0.0621 0.0587 0.0848 0.0751 0.0425 0.0163 0.0750 0.0980 0.0588 0.0164 P2O5 0.0146 0.0187 0.0115 -0.0116 0.0116 0.0055 0.0060 0.0004 -0.0010 0.0309 0.0024 0.0088 -0.0032 0.0014 0.0053 BaO -0.0431 0.0108 0.1399 -0.1183 0.1075 0.0323 0.0647 -0.0323 0.0933 0.0323 -0.0215 -0.0108 -0.0215 0.1516 -0.0108 Ce2O3 -0.0518 0.0307 0.0157 0.0188 0.0266 0.0557 0.0730 -0.0137 -0.0335 -0.0454 -0.0498 0.0208 0.0204 0.0883 0.1032 Cr2O3 -0.0113 0.0047 -0.0011 0.0037 0.0015 0.0017 -0.0225 0.0073 -0.0249 0.0193 -0.0335 -0.0142 -0.0697 0.0026 0.0076 MnO 0.0327 0.0232 0.0178 0.0620 0.0499 0.0003 0.0431 0.0885 0.0655 0.0027 0.1090 0.0611 -0.0320 0.0673 0.1043 SrO -0.0013 -0.0671 -0.0355 -0.0366 -0.0288 -0.0262 0.0275 -0.0445 -0.0199 -0.0235 -0.0158 -0.0406 -0.0735 -0.0085 -0.0433 Rb2O -0.9188 -0.8456 -0.9233 -0.9310 -0.9237 -0.8722 -0.9333 -0.9206 -0.9337 -0.9432 -0.9336 -0.9374 -0.9671 -0.9500 -0.9488 Total 97.1782 95.6844 95.1082 96.9273 94.0670 95.5368 96.5837 95.3296 90.8759 96.6681 95.9079 96.4866 93.5344 95.2977 95.9124 181 Eleme nt Tejpur/ 1 Tejpur/ 2 Tejpur/ 3 Tejpur/ 4 Tejpur/ 5 Tejpur/ 6 Tejpur/ 7 Tejpur/ 8 Tejpur/ 9 Tejpur/ 10 Tejpur/ 11 Tejpur/ 12 Tejpur/ 13 Tejpur/ 14 Tejpur/ 15 Na2O 2.9947 3.0949 4.2822 3.0656 2.9962 2.9983 3.0643 3.1139 2.9601 4.1942 3.3020 2.9263 0.1480 3.0565 3.0222 SiO2 73.6086 74.3868 52.6870 72.7517 75.2743 74.8031 74.7646 74.4110 74.3810 53.0995 74.6737 73.0041 99.7105 74.4392 74.2693 K2O 5.1567 5.2501 0.2471 5.1116 5.3122 5.0815 5.1837 4.8738 5.1184 0.3409 5.2204 5.1674 0.0641 4.9115 4.9840 CaO 0.8243 0.6614 12.4008 0.7446 0.6899 0.6766 0.7837 0.7811 0.7587 12.6787 0.6202 0.9179 0.0517 0.8189 0.7586 TiO2 0.0700 0.0505 0.1020 0.0505 0.0132 0.0869 0.0427 0.0265 0.0442 0.1373 0.0861 0.0382 -0.0048 0.0274 0.0343 FeO 0.9668 1.0140 0.6035 1.1301 0.9043 1.0467 0.9441 0.5636 1.0394 0.1931 0.9204 1.0315 0.0306 0.6320 1.0120 Al2O3 11.9954 11.8608 27.8533 11.6943 11.9445 11.2407 11.7105 11.5915 11.7420 28.8183 11.8637 11.6604 0.5550 11.5954 11.6812 MgO 0.0686 0.0033 0.0760 0.0556 0.0784 0.0261 0.0816 0.0586 0.0652 0.1908 0.0065 0.0622 0.0541 0.0587 0.0425 P2O5 0.0061 0.0042 0.0081 0.0078 0.0134 -0.0131 -0.0033 0.0048 0.0089 0.0049 0.0101 0.0084 -0.0132 0.0136 0.0075 BaO 0.1280 0.0645 0.0816 0.0467 0.1395 0.0931 -0.1167 0.0754 0.0000 0.0539 0.0116 0.2449 0.0433 0.1723 0.0858 Ce2O3 0.0953 -0.0665 -0.0899 -0.0981 -0.0980 -0.0127 0.0204 0.0263 -0.0184 0.0380 -0.0428 0.0416 -0.0560 -0.0341 0.0207 Cr2O3 -0.0201 -0.0278 0.0259 0.0077 0.0012 -0.0700 -0.0026 0.0271 0.0154 0.0396 -0.0135 0.0220 0.0000 0.0022 0.0054 MnO 0.0222 0.1070 0.0061 0.0860 0.0859 0.0056 0.0745 0.0666 -0.0340 -0.0153 0.0667 0.0769 -0.0120 0.0545 0.0719 SrO 0.0057 -0.0249 -0.0091 0.0028 -0.0366 -0.0622 -0.0738 -0.0484 -0.0445 0.0601 -0.0638 0.0227 -0.0423 -0.0039 -0.0091 Rb2O -0.9488 -0.9175 -10.533 -0.9193 -0.9529 -0.9354 -0.9615 -0.9194 -0.9166 -10.555 -0.8959 -0.9610 -0.9210 -0.9568 -0.9174 Total 95.9424 96.4975 98.3737 94.7552 97.4531 96.0586 96.6701 95.6201 96.1333 99.8494 96.7814 95.2245 100.6572 95.7822 95.9953