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dc.contributor.authorEvans, Nicholas Philip
dc.date.accessioned2019-03-04T10:18:52Z
dc.date.available2019-03-04T10:18:52Z
dc.date.issued2019-03-30
dc.date.submitted2018-09-30
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/290136
dc.description.abstractTriple oxygen and hydrogen isotope analysis of the structurally-bound water in gypsum can provide a direct measure of past hydrologic variability. This thesis presents the development of the water extraction and isotopic measurement procedures, the calculation of the gypsum-water isotope fractionation factors, and the application of the method to constrain the palaeohydrologic conditions in two temporally and geographically disparate sites. Measurement of the isotopic composition of gypsum hydration water is used to examine the hydrological changes that occurred during the Terminal Classic Drought of the Maya lowlands (~800-1000 CE), coincident with the period when the Classic Maya Civilization of Mesoamerica collapsed. The data provide a complete and direct archive of hydrological conditions that have previously been limited to ice core records. Mean annual rainfall is shown to have decreased by between 41% and 54%, with intervals of up to 70%, compared to present-day conditions. This study has also shown for the first time that relative humidity was 2%-7% lower during the Terminal Classic Drought compared to today. The methodology is also applied to the massive gypsum deposits in the marginal and deep basins of the Mediterranean to interpret the chemical evolution of parent water bodies during the Messinian Salinity Crisis (5.97-5.3 Ma). By combining the measurement of gypsum hydration water with other traditional (e.g. strontium) and novel (e.g. calcium and barium) isotope tracers, the hydrological changes during the deposition of Primary Lower Gypsum units of the Sorbas Basin in southeastern Spain, the Upper Gypsum units of Sicily, and deep basin deposits have been constrained. The results indicate that all deposits experienced a significant freshwater contribution to the mother fluids from which they formed. It is proposed that obliquity-controlled sea level and eccentricity-modulated precession, superimposed on longer-term tectonic restriction of the Mediterranean-Atlantic exchange, together controlled the varying depositional environments during the formation of the Messinian Salt Giant. This thesis demonstrates that the analysis of gypsum hydration water is a powerful tool for palaeoclimate reconstruction. The methodology can be applied to gypsum (and other hydrated minerals) in a wide range of settings across geological space and time, providing a rich source of information about the environmental conditions under which they formed.
dc.description.sponsorshipThis research was supported by the ERC WIHM Project #339694 to DAH.
dc.language.isoen
dc.rightsAll rights reserved
dc.subjectClimate
dc.subjectGypsum hydration water
dc.subjectFractionation factors
dc.subjectClassic Maya civilization
dc.subjectMaya
dc.subjectTerminal Classic Drought
dc.subjectDrought
dc.subjectMessinian Salinity Crisis
dc.subjectTriple oxygen isotopes
dc.subjectStable isotopes
dc.subjectIsotopes
dc.subjectGypsum
dc.subjectCalcium Sulfate
dc.subjectPalaeoclimate
dc.subjectHydrated minerals
dc.subjectEvaporites
dc.titleIsotope Systematics of Gypsum and its Hydration Water
dc.typeThesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnameDoctor of Philosophy (PhD)
dc.publisher.institutionUniversity of Cambridge
dc.publisher.departmentEarth Sciences
dc.date.updated2019-03-02T19:19:15Z
dc.identifier.doi10.17863/CAM.37364
dc.contributor.orcidEvans, Nicholas Philip [0000-0002-9813-8811]
dc.publisher.collegeClare
dc.type.qualificationtitlePhD in Geochemistry
cam.supervisorHodell, David A
cam.supervisor.orcidHodell, David A [0000-0001-8537-1588]
cam.thesis.fundingfalse
rioxxterms.freetoread.startdate2020-03-04


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