HR: 0800h
AN: PP11B-0529    [Abstracts]
TI: The variation of monsoon precipitation in central China since last deglaciation
AU: * Cai, Y
EM: yanjun_cai@ieecas.cn
AF: Insitute of Earth Environment, CAS, #10 Fenghui South Road, Xi'an High-Tech Zone, Xi'an, 710075, China
AU: Tan, L
EM: tanlch@ieecas.cn
AF: Insitute of Earth Environment, CAS, #10 Fenghui South Road, Xi'an High-Tech Zone, Xi'an, 710075, China
AU: Cheng, H
EM: cheng021@umn.edu
AF: Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455, United States
AU: Edwards, R
EM: edwar001@umn.edu
AF: Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455, United States
AU: Kong, X
EM: kongxinggong@njnu.edu.cn
AF: College of Geography Science, Nanjing Normal University, Nanjing, 210097, China
AU: Wang, X
EM: wang0452@umn.edu
AF: Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455, United States
AU: An, Z
EM: anzs@loess.llqg.ac.cn
AF: Insitute of Earth Environment, CAS, #10 Fenghui South Road, Xi'an High-Tech Zone, Xi'an, 710075, China
AB: We analyzed two stalagmites (C996-1 and C996-2) collected from Jiuxian Cave in Zhashui County, Shaanxi Province, central China. Thirty-eight ²³⁰Th dating results shown that the stalagmite C996-1 continuously deposited through last 8.5 ka BP (before present) and C996-2 grew through last 19.0ka BP except two hiatuses between 5.7 and 8.3 ka BP, and 11.9 and 15.4 ka BP, respectively. Considering dating errors and resolution differences, the δ¹⁸O variation of these two stalagmites are similar during the intervals of contemporaneous growth. Moreover, Hendy tests show that these two stalagmites deposited under isotopic equilibrium conditions. It means that oxygen isotopic variations are primarily caused by climate change. We interpret our δ¹⁸O records in terms of summer monsoon precipitation changes, although the temperature might have some minor impacts, as it affects the δ¹⁸O of the precipitation during the winter season and the fractionation between deposited calcite and drip water. The δ¹⁸O records show notable changes within the LGM, resembling other East Asian monsoon records, such as those from Hulu and Dongge Caves, suggest that significant climatic variability occurred in monsoonal eastern Asia during the LGM interval. We compared our record to other precisely dated contemporaneous speleothem records from Hoti, Hulu, Heshang and Sanbao Caves. The increasing trend of the δ¹⁸O commenced as early as 7.5 ka BP in low latitude monsoonal area, i.e. Hoti Cave, while get later toward higher latitude such as 7.0 ka BP in Dongge Cave, 5.3 kaBP in Heshang Cave, 4.7 ka BP in Sanbao Cave and 4.3 ka BP in Jiuxian Cave. It suggested that the summer monsoon precipitation in East Asia may change asynchronously in central and eastern China in the Holocene, started to decrease at different times in different regions. The asynchronous precipitation changes may be related to the responses of a coupled tropical and subtropical monsoon system to the changes of the insolation as well as the differences in the thermal forcing which result from the complex topography.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1120 Isotopic disequilibrium dating
DE: 1626 Global climate models (3337, 4928)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting