Lake evolution and hydroclimate variation at Lake Qinghai (China) over the past 32 ka inferred from ostracods and their stable isotope composition
Lake evolution and hydroclimate variation at Lake Qinghai (China) over the past 32 ka inferred from ostracods and their stable isotope composition
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DOI：
10.1007/s10933-017-9979-6
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发表时间：
2017-06
影响因子：
2.1
通讯作者：
Xiangzhong Li;Weiguo Liu
中科院分区：
文献类型：
--
作者：
Xiangzhong Li;Weiguo Liu
我们利用青海湖中国32米沉积岩芯中介形类的种类组合及其δ18O值，以及从湖中其他地点采集的岩芯信息，推断了自上一次冰期以来的湖泊演化和水气候变化。介形类优势种--迟缓介形类及其低的δ18O值表明，青海湖面积较小，甚至由多个普拉湖组成，15.0ka之前的寒冷和干燥气候条件下，1F核心位置甚至可能处于湿地环境。低δ~(18)O值的患者中存在低氧血症，且不存在I。在15.0千卡之后，表明湖泊面积增加或游玩合并。高δ18O值的介形类减少或消失表明，在12.0~11.6亿ka的干旱气候下，湖泊萎缩。11.6年后，介形类(Eucypris mareotica和L.它们的δ18O值如下：(1)11.6-7.4千卡--较大但仍然较小的湖泊面积，在主要干燥的气候条件下，具有更大的水分有效性；(2)7.4千卡--在较温暖和潮湿的气候下，湖泊水位上升；(3)3.2千卡--到现在--稳定的大型微咸水湖泊。青海湖面积较小时，由于湖水流量径流比低，核心点与河口淡水接近，导致青海湖面积较小时，介形虫δ18O值相对较低。介形类δ18O值在冰期间期和整个末次冰盛期和早期(约24.0-16.0kA)较低，是由于冰雪季节性融水的贡献较大，以及与当时该地区寒冷气候条件有关的低降水量δ18O造成的。
We used ostracod species assemblages and their δ18O values in a 32-m sediment core from Lake Qinghai, China, along with information from cores collected at other sites in the lake, to infer lake evolution and hydroclimate changes since the last glacial. Dominant ostracod speciesIlyocypris bradyiand its low δ18O values showed that Lake Qinghai was small in size or even consisted of several playa lakes, and the 1F core site could have even been in a wetland setting, under cold and dry climate conditions before 15.0 ka. Presence ofLimnocythere inopinatawith low δ18O values, and absence ofI. bradyiafter 15.0 ka, indicate the lake area increased or that the playas merged. The decrease or disappearance of ostracods with high δ18O values showed that the lake shrunk under dry climate from 12.0 to 11.6 ka. After 11.6 ka, hydroclimate shifts inferred from ostracod species changes (Eucypris mareoticaandL. inopinata) and their δ18O values were as follows: (1) 11.6–7.4 ka—larger, but still small lake area with greater moisture availability under primarily dry climate conditions, (2) 7.4 to 3.2 ka—increasing lake level under a warmer and wetter climate, and (3) 3.2 ka to present—stable, large, brackish lake. The low ratio of lake water volume to runoff, and close proximity of the core site to freshwater input from the river mouth would have resulted in relatively lower ostracod δ18O values when Lake Qinghai was small in area during the interval from 32.0 to 15.0 ka. Lower ostracod δ18O values during interstadials and throughout the entire Last Glacial Maximum and early deglacial (ca. 24.0–16.0 ka) were caused by a greater contribution of seasonal meltwater from ice or snow and low incoming precipitation δ18O values related to cold climate conditions in the region at that time.