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dc.contributor.authorGiesche, Alena
dc.description.abstractThis thesis investigates the paleoclimate of the Indus River Basin and surrounding areas of northwest (NW) South Asia over the last 12,000 years, covering a critical period of human history. The region’s climate is characterized by two overlapping rainfall systems: the Indian Summer Monsoon (ISM) and the Indian Winter Monsoon (IWM). A shift in these monsoon systems has been documented throughout South Asia at 4.2 ka BP, with potential effects on the development and decline of the Indus Civilization (c. 5- 3.6 ka BP). This thesis examines the connection between climate and cultural shifts by providing new records from three climate archives spanning 1500 km from the Arabian Sea to the Thar Desert and Himalayan Mountains. The chapters feature δ¹⁸O and δ¹³C of three foraminifer species in marine core 63KA over 8.8-7.6 ka BP and 5.4-3.0 ka BP, gypsum from three Holocene Thar Desert playa lakes, and sub-annually resolved trace element and stable isotope data from DHAR-1 speleothem covering 4.2-2.5 ka BP. The major findings from this thesis contribute to a more comprehensive understanding of climate change in NW South Asia throughout the Holocene. The three Thar Desert playa lakes began accumulating gypsum c. 11 ka BP, aligning with a post- glacial strengthening ISM. Prismatic gypsum crystals and uniformly high δ¹⁸O of gypsum hydration water from early-mid Holocene deposits suggest relatively deep lake levels during this phase. Similarly, the δ¹⁸O of marine core 63KA foraminifer species dwelling in surface and thermocline layers demonstrate a stronger ISM over 8.8-7.6 ka BP and a strengthening IWM from 8.8-8.6 ka BP. By 4.8 ka BP, the ISM started weakening, but IWM strength peaks from 4.5-4.3 ka BP. A wet period c. 5-4.4 ka BP is also apparent from high δ¹⁸O of gypsum hydration water at Karsandi playa. The late Holocene droughts after 4.2 ka BP are well-documented by the precise (age error ± 18 years) DHAR-1 reconstruction, which tracks ISM strength via δ¹⁸O and winter aridity using δ¹³C, Sr²⁺ U²⁺, and Ba²⁺. Weakened ISM and IWM both contributed to the 230-year drought period with three distinct arid phases (4.2-4.17 ka BP, 4.14-4.08 ka BP, and 4.06-3.97 ka BP). Core 63KA shows minimum Indus River discharge and weakened IWM over the same interval, whereas Lunkaransar playa shows a protracted lake level decline, and aeolian sand replaces gypsum deposition at Karsandi by 3.2 ka BP. Shallow playa systems briefly recover at Lunkaransar and Khajuwala during the late Holocene, but Khajuwala eventually desiccates permanently.
dc.description.sponsorshipTworains ERC grant 648609 WIHM ERC grant 339694 QUEST H2020 Marie Skodowska-Curie actions 691037
dc.rightsAll Rights Reserved
dc.subjectMarine core
dc.subjectGypsum hydration water
dc.subjectIndus civilization
dc.subjectIndian Summer Monsoon
dc.subjectIndian Winter Monsoon
dc.titleA Multi-Archive Reconstruction of Holocene Summer and Winter Monsoon Variability in NW South Asia
dc.type.qualificationnameDoctor of Philosophy (PhD)
dc.publisher.institutionUniversity of Cambridge
dc.contributor.orcidGiesche, Alena [0000-0003-3673-7269]
dc.type.qualificationtitlePhD in Earth Sciences
pubs.funder-project-idEuropean Commission Horizon 2020 (H2020) Marie Sk?odowska-Curie actions (691037)
cam.supervisorHodell, David
cam.supervisor.orcidHodell, David [0000-0001-8537-1588]

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