Ostracod Mg/Sr/Ca and 87Sr/86Sr geochemistry from Tibetan lake sediments: Implications for early to mid‐Pleistocene Indian monsoon and catchment weathering

Jin, Zhangdong and Bickle, Mike J. and Chapman, Hazel J. and Yu, Jimin and An, Zhisheng and Wang, Sumin and Greaves, Mervyn J. (2011) Ostracod Mg/Sr/Ca and 87Sr/86Sr geochemistry from Tibetan lake sediments: Implications for early to mid‐Pleistocene Indian monsoon and catchment weathering. Boreas, 40 (2). pp. 320-331. ISSN 0300-9483 DOI 10.1111/j.1502-3885.2010.00184.x

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Abstract

Lacustrine sediment serves as a valuable archive for tracing catchment weathering processes associated with past climatic and/or tectonic changes. High-resolution records of fossil ostracod Mg/Ca, Sr/Ca and 87Sr/86Sr ratios from a lake sediment core from the central Tibetan Plateau reveal a temporal link between lake-water chemistry and catchment weathering and distinct monsoonal oscillations over the early to mid-Pleistocene. Between 2.01 and 0.95 Ma, lake-water chemistry was dominated by a high proportion of carbonate weathering related to variations in the Indian monsoon, resulting in relatively low and constant ostracod 87Sr/86Sr but obvious fluctuations in Mg/Ca, Sr/Ca and δ18O. Across the mid-Pleistocene transition (MPT), a significant increase in 87Sr/86Sr and frequently fluctuating ratios of ostracod Mg/Ca, Sr/Ca and δ18O are coincident with increases in both Chinese loess grain size and Arabian Sea lithogenic flux. This correlation indicates an increased glaciation and a strong monsoon seasonal contrast over the plateau. The increase in lake-water 87Sr/86Sr across the MPT highlights a change in catchment weathering patterns, rather than one in climate-enhanced weathering intensity, with an increased weathering of 87Sr-rich minerals potentially induced by marked extensive glaciation and strong seasonality in the central plateau.

Item Type: Article
Uncontrolled Keywords: 2011AREP; IA63;
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
02 - Geodynamics, Geophysics and Tectonics
Divisions: 02 - Geodynamics, Geophysics and Tectonics
Journal or Publication Title: Boreas
Volume: 40
Page Range: pp. 320-331
Identification Number: 10.1111/j.1502-3885.2010.00184.x
Depositing User: Sarah Humbert
Date Deposited: 19 Jul 2011 14:35
Last Modified: 23 Jul 2013 10:02
URI: http://eprints.esc.cam.ac.uk/id/eprint/2117

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