柴达木盆地尕海湖沉积物粒度特征及其古气候意义

GRAIN-SIZE CHARACTERISTICS AND THEIR ENVIRONMENTAL SIGNIFICANCE OF GAHAI LAKE SEDIMENTS IN QAIDAM BASIN

以尕海湖DG02钻孔沉积物为研究对象,利用高分辨率的粒度数据,结合岩性、孢粉特征,分析其粒度特征及近11000aBP来的气候环境变化。研究发现,尕海湖沉积物记录了该区域湖泊水体逐渐上升又逐渐减少的过程,气候环境变化大致分为4个阶段:(1)冰消期晚期(11324～10290aBP)气候干旱,湖泊水位下降,面积收缩,水动力较强,沉积颗粒较粗;(2)早全新世(10290～8850aBP),气候转向湿润,湖泊水位上升,为浅水至深水的过渡阶段,颗粒由粗变细;(3)中全新世(8850～4400aBP),气候更加湿润,湖水水位达到最高,面积扩大,水动力达到最弱,沉积颗粒最细;(4)晚全新世(4400～200aBP),气候变干,湖泊强烈收缩,湖面下降,水动力达到最强,沉积颗粒最粗。尕海湖DG02钻孔沉积物粒度所记录的区域气候干湿变化及一些重要的干湿事件与国内外研究显示出较好的一致性。

This article analyzes characteristics of grain-sizes and changes of climate and environment since about 11 000 aBP ago using high-resolution grain-size data and information of lithology and pollen assemblage from core DG02 in Gaihai Lake.The research result shows that sediment in Gahai Lake has well recorded the processes of the lake water from wetting-up to drying-up.The climatic changes can be divided into four stages as follows：late deglaciation（11 324~10 290 aBP）,when the lake level was low,the area was shrinking,the driving force was strong and the sediment particles were coarse with arid climate;early Holocene（10 290~8 850 aBP）,when the lake water level was high,the sediment particles were fine with wet climate in the transition phase;mid Holocene（8 850~4 400 aBP）,when the lake water level was much lower and expanding,the driving force was the weakest and the sediment particles were the finest with wet climate;late Holocene（4 400~200 aBP）,when the lake water level was low and shrinking,the driving force was strong and the sediment particles were coarse with arid climate.The climatic changes and important dry and wet events in Gahai Lake area were coincident with other research results at home and abroad.