WANG Yong1,2,3, SHEN Ji1*, XU Xingna1,4, LIU Xingqi1, SIROCKO Frank3, ZHANG Enlou1, and JI Junfeng5
(1 State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Nanjing 210008, China
2 Max Planck Institute of Chemistry, Mainz 55020, Germany
3 Institute of Geoscience, University of Mainz, Mainz 55099, Germany
4 School of Geographical Science, Southwest University, Chongqing 400715, China
5 Department of Earth Sciences, Nanjing University, Nanjing 210093, China )
Abstract A 475-cm long sediment core (QH-2005) from Lake Qinghai was used to carry out multi-proxy analysis of δ18O and body length of ostracod valves and redness and grain size of sediments, in order to reconstruct environmental changes during the past 13500 cal. a BP. The age model was based on 6 14C dates for bulk orgnic carbon (BOC) and 2 14C dates for lignin. The lignin 14C dates are apparently younger than the corresponding layers’ BOC 14C dates, indicating that the reservoir age varied from 728 to 1222 a since the Late Glacial and from 2390 to 2490 a immediately before the pre-bomb era. Hence, the 14C age model for Core QH-2005 was corrected by the changing reservoir age. Ostracod δ18O values were primarily related to dilution and evaporative enrichment of the lake water. The reconstructed salinity based on ostracod body length coincides well with ostracod δ18O values. High redness and mean grain size (MZ) values indicate increased riverine supply to Lake Qinghai associated with increasing monsoon rainfall. Multi-proxy results show that climate during 13500–10900 cal. a BP was relatively cold and dry with frequent short-term fluctuations; a warm and wet climate began at about 10900 cal. a BP and culminated around 6500 cal. a BP as a result of monsoon strengthening; the climate became cold and dry afterwards and has remained relatively stable since 3400 cal. a BP. Our data also reveal short-term (millennial/centennial timescales) climatic fluctuations including: Younger Dryas events, ice-rafting events 8 and 1 (by ~11000 cal. a BP and ~1600 cal. a BP respectively), 8200 cal. a BP cold event, Little Ice Age and the Medieval Warm Period.
Key words ostracod oxygen isotope; ostracod body length; redness; grain size; environmental change; Lake Qinghai
* Corresponding author, E-mail: jishen@niglas.ac.cn
CHINESE JOURNAL OF GEOCHEMISTRY Vol. 30, No. 4, 2011, page 479-489
© Science Press and Institute of Geochemistry, CAS and Springer-Verlag Berlin Heidelberg 2011
