末次冰盛期时吉兰泰盐湖的湖泊状态与古气候特征

通过现代季风边缘区的吉兰泰盐湖钻孔JLT11-A孔沉积岩芯的矿物分析,结合地层盘星藻的含量探讨末次冰盛期(LGM)时湖泊的状态和古气候特征。结果显示:在LGM时吉兰泰湖泊沉积矿物主要是石英、长石为主的碎屑岩沉积,含量在85%左右,显示出陆源碎屑矿物的高输入状态,可能指示区域寒冷干旱的环境;其次是以方解石为主的碳酸盐的沉积,含量约为10%;氯化物为主的石盐类矿物一般不足5%,但持续存在,指示湖泊仍然有较高的盐度,因此地层中的淡水藻类盘星藻可能是由河流输入。由于陆源碎屑矿物输入强烈,矿物组合可能难以直接指示吉兰泰盐湖湖水状态。区域的干冷的气候与大多数的古气候记录一致,而与新疆西部的冷湿的环境不同。对比邻近区域的古气候研究结果发现,本区域在LGM时段夏季降水相对于冰消期偏多,而相对于MIS3阶段晚期偏少,整体夏季风减弱。吉兰泰盐湖末次冰盛期到末次冰消期以来矿物组合的变化表明,湖泊环境可能受到夏季太阳辐射、全球与区域温度变化以及夏季风强弱变化的影响。

Lake Status and Palaeoclimate in Jilantai Salt Lake Area during the Last Glacial Maximum

This study is trying to reconstruct the lake status and regional palaeoclimate character based on XRD data and Pediastrum algae from the core JLT11-A of Jilantai Salt Lake during the Last Glaical Maximum (LGM). The result suggested that the main minerals of the sediments were clastics (~85%) dominated by Quartz and Albite and about 10% of carbonates (mainly calcite), and both of them could be transported from land by strong winds, thus indicated a cold-dry climate as other palaeoclimatic records suggested. Although the sum of Chloride and sulfate minerals were generally less than 5%, its continuous appearance of Chloride suggested a basically high salinity. Therefore, the Pediastrum was not possible from the lake, but was transported by rivers. Mineral assemblage of Jilantai Lake is more connected with terrestrial material input and it is difficult to directly trace the lake water salinity. By comparing to the other records from neighboring regions, the LGM summer precipitation was higher than deglaciation period, while, it was lower comparing to the late MIS3 stage. The pattern of Jilantai Salt Lake evolution from LGM to the Last Deglaciation suggested that the mineral assemblage variations and lake status were strongly affected by the summer insolation, global and regional temperature, and Asian summer monsoon intensity.