报告题目：Biomarker evidence for a huge ice-dammed lake-drainage in the Arctic Ocean 

　　报告人：  Dr. Ludvig L？wemark（ National Taiwan University） 

　　报告时间：2017年11月7日下午2:30 

　　报告地点：加速器质谱中心一楼报告厅 

　　Ludvig L？wemark报告摘要： 　 

               
　　The Arctic Ocean plays an important role in the global climate system primarily through its influence on Earth’s albedo caused by variations in sea-ice cover, and through the Arctic’s contribution to the formation of the North Atlantic Deep Water (NADW), which is considered to be the main driver of the global thermohaline circulation. Moreover, recent studies have emphasized the importance of teleconnections tying variations in sea-ice cover to shifts in the SE Asian monsoon system. However, despite its importance we still know surprisingly little about the processes controlling past Arctic climate changes, and even to establish reliable age models for Arctic Ocean sediment cores still pose a major challenge. 

　　In many cores from the Eurasian side of the Arctic Ocean, a distinct, dark gray layer can be found in the strata roughly corresponding to a time interval around the boundary between Marine Isotope Stages (MIS) 3 and 4. The layer is characterized by a sharp lower boundary, abundant ice rafted debris, scarce (or complete lack of) microfossils and bioturbation, and extremely low concentrations of Mn in the sediment. These sedimentary parameters are strongly suggestive of an extremely rapid event best explained by a catastrophic drainage of an ice-dammed lake on the Siberian hinterland. 

　　Here we use Nd and Sr isotopes in combination with clay mineralogy to pin point the source of this layer to the region south of the Kara Sea near the Putorana basalt plateau. The interpretation of the gray layer as the result of an ice-dammed lake-drainage is further supported by biomarker studies showing an enrichment of branched glycerol dialkyl glycerol tetraethers, which are primarily produced in soils. 

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