Holocene variations in the Asian monsoon inferred from the geochemistry of lake sediments in central Tibet
Holocene variations in the Asian monsoon inferred from the geochemistry of lake sediments in central Tibet
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DOI：
10.1016/j.yqres.2005.02.014
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发表时间：
2006-03-01
影响因子：
2.3
通讯作者：
Tang, LY
中科院分区：
文献类型：
--
作者：
Morrill, C;Overpeck, JT;Tang, LY
我们提出了一个记录的季风变化的早，中全新世，推断从沉积物的地球化学从阿洪错，在西藏中部的湖泊。该记录的分辨率优于50年，年龄模型来自陆地木炭的放射性碳年龄，消除了与湖泊硬水效应相关的误差。我们进行了碳酸盐%、有机碳%、有机质C/N和δ C-13、碳酸盐δ C-13和δ O-18以及白云石%的井下地球化学测量。代理校准和现代水平衡重建表明，这些都是湖泊深度和季风降水量的代理。我们发现，湖泊水位和季风降水一直在减少，在Ahung公司早全新世以来（类似于7500卡年B. P。）。叠加在这一趋势是季风降雨量在7000-7500和4700卡年BP和七个世纪尺度的干湿振荡的快速下降。岩芯不含沉积物从最后类似4000年。然而，湖泊的表层沉积物在世纪积累起来。由此，我们认为，湖泊水位最近再次上升后，晚全新世干旱期。(c)2005年华盛顿大学。All rights reserved.
We present a record of monsoon variations for the early and middle Holocene that is inferred from the geochemistry of sediment cores from Ahung Co, a lake in central Tibet. The resolution of this record is better than 50 yr and the age model is derived from radiocarbon ages of terrestrial charcoal, which eliminates errors associated with the lake hard-water effect. We made down-core geochemical measurements of % carbonate, % organic carbon, C/N and delta C-13 of bulk organic matter, delta C-13 and delta O-18 of carbonate, and % dolomite. Proxy calibration and modern water-balance reconstruction show that these are proxies for lake depth and the amount of monsoon precipitation. We find that lake level and monsoon precipitation have been decreasing at Ahung Co since the early Holocene (similar to 7500 cal yr B.P.). Superimposed on this trend are rapid declines in monsoon rainfall at 7000-7500 and 4700 cal yr B.P. and seven century-scale wet-dry oscillations. The cores do not contain sediment from the last similar to 4000 yr. Surface sediments from the lake accumulated during the 20th century, however. From this, we argue that lake levels have risen again recently following a late Holocene dry period. (c) 2005 University of Washington. All rights reserved.