Environmental changes during the past 13500 cal. a BP deduced from lacustrine sediment records of Lake Qinghai, China  

作　　者：WANG Yong SHEN Ji XU Xingna LIU Xingqi SIROCKO Frank ZHANG Enlou JI Junfeng 

机构地区：[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 ofMainz, Mainz 55099, Germany [4]School of Geographical Science, Southwest University, Chongqing 400715, China [5]Department of Earth Sciences, Nanjing University, Nanjing 210093, China

出　　处：《Chinese Journal Of Geochemistry》2011年第4期479-489,共11页中国地球化学学报

基　　金：supported jointly by the National Basic Research Program of China (No.2010CB833404);the Nanjing Institute of Geography and Limnology, CAS (NIGLAS2011KXJ002);the National Natural Science Foundation of China for Distinguished Young Scholars (No.40625007);the National Natural Science Foundation of China (Nos.40872117 and 40902047);the Knowledge Innovation Program of the Chinese Academy of Sciences (No.NIGLAS2009QD03)

摘　　要：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 environ-mental 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 fre-quent 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 rela-tively stable since 3400 cal. a BP. Our data also reveal short-term (millennial/centennial timescales) climatic fluctua-tions including: Younger Dryas events, ice-rafting events 8 and 1 (by ～11000 cal. a BP and ～1600 cal. a BP respec-tively), 8200 cal. a BP cold event, Little Ice Age and the Medieval Warm Period.A 475-cm long sediment core （QH-2005） from Lake Qinghai was used to carry out multi-proxy analysis of 6180 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 Qinghal 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 respec- tively）, 8200 cal. a BP cold event, Little Ice Age and the Medieval Warm Period.

关 键 词：CAL 湖泊沉积记录 青海湖 BP 环境 平均晶粒尺寸 气候变化 中国 

分 类 号：P532[天文地球—古生物学与地层学] TS934.3[天文地球—地质学]