Dynamics of the last four glacial terminations recorded in Lake Van, Turkey
Dynamics of the last four glacial terminations recorded in Lake Van, Turkey
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DOI：
10.1016/j.quascirev.2014.07.001
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发表时间：
2014-11-15
影响因子：
4
通讯作者：
Haug, Gerald H.
中科院分区：
文献类型：
--
作者：
Kwiecien, Ola;Stockhecke, Mona;Haug, Gerald H.
一套年代确定的Van湖气候代用资料记录了土耳其安纳托利亚东部4个冰期/间冰期旋回的环境变化。从花粉、有机碳、自生碳酸盐含量、XRF元素谱和岩性分析中得出的干冷冰期和暖湿间冰期的图像与经典的碳酸盐氧同位素组成解释不一致，表明Van湖地区的碳酸盐氧同位素组成模式更为复杂。对冰期终止的详细分析允许约束沉积模式，解释在所有代用物中观察到的不同模式。我们假设降水、融雪和冰川融水补给相对贡献的变化对凡湖的所有沉积过程都起着非常重要的作用。以融雪补给为主的冰湖凡湖水位较低，水柱为含氧水柱，尾层沉积的碳酸盐记录了入流的轻同位素特征。在终止期间，降雨量增加和山地冰川融水的大量供应导致湖泊水位上升。降雨增加增加了水柱的密度梯度，阻碍了混合，导致底层缺氧的发展。在终止过程中沉淀的碳酸盐在其同位素组成中显示出很大的波动。凡湖的全间冰期条件以高水位或缓慢下降为特征。降雨和融雪为湖泊提供补给，但由于重新建立的混合，自生碳酸盐的同位素组成比代表融雪和大气降水的径流的同位素组成更重，更接近蒸发影响的湖泊水的同位素组成。(C) 2014 Elsevier Ltd.版权所有。
A well-dated suite of Lake Van climate-proxy data covering the last 360 ka documents environmental changes over 4 glacial/interglacial cycles in Eastern Anatolia, Turkey. The picture of cold and dry glacials and warm and wet interglacials emerging from pollen, organic carbon, authigenic carbonate content, elemental profiling by XRF and lithological analyses is inconsistent with classical interpretation of oxygen isotopic composition of carbonates pointing to a more complex pattern in Lake Van region. Detailed analysis of glacial terminations allows for the constraining of a depositional model explaining different patterns observed in all the proxies. We hypothesize that variations in relative contribution of rainfall, snowmelt and glacier meltwater recharging the basin have a very important role for all sedimentary processes in Lake Van. Lake level of glacial Lake Van, predominantly fed by snowmelt, was low, the water column was oxic, and carbonates precipitating in the epilimnion recorded the light isotopic signature of inflow. During terminations, increasing rainfall and significant supply of mountain glaciers' meltwater contributed to lake level rise. Increased rainfall enhanced density gradients in the water column, and hindered mixing leading to development of bottom-water anoxia. Carbonates precipitating during terminations show large fluctuations in their isotopic composition. Full interglacial conditions in lake Van are characterized by high or slowly falling lake level. Rainfall and snowmelt feed the lake but due to re-established mixing, the isotopic composition of authigenic carbonates is heavier and closer to that of evaporation-influenced lake water than that of runoff representing snowmelt and atmospheric precipitation. (C) 2014 Elsevier Ltd. All rights reserved.