晚冰期以来共和盆地更尕海碎屑物质输入过程与气候变化  

PROCESSES OF EXOGENOUS DETRITAL INPUT TO GENGGAHAI LAKE AND CLIMATIC CHANGES IN THE GONGHE BASIN SINCE THE LATE GLACIAL

作　　者：李渊[1] 强明瑞[1] 王刚刚[1] 李丰山[1] 刘英英[1] 金彦香[1] 李昊[1] 金明[1] 

机构地区：[1]兰州大学西部环境与气候变化研究院,西部环境教育部重点实验室,兰州730000

出　　处：《第四纪研究》2015年第1期160-171,共12页Quaternary Sciences

基　　金：国家自然科学基金项目（批准号：41271219）、高等学校博士学科点专项科研基金项目（批准号：20130211110035）和兰州大学中央高校基本科研业务费专项项目（批准号：lzujbky-2014-261和lzujbky-2011-82）共同资助

摘　　要：湖泊碎屑物质输入过程的认识对于探讨区域环境演化历史具有重要的意义.采用高分辨率X射线荧光光谱（XRF）扫描分析法,对更尕海沉积岩芯进行了元素测试.沉积岩芯中元素Si等的变化主要由外源碎屑物质输入而贡献.结合粗颗粒组分含量的变化,沉积岩芯的元素含量可以用来指示湖泊碎屑物质的输入过程及其变化.结果表明,晚冰期气候寒冷干旱,风化程度低,湖泊碎屑物质输入过程较弱且以风力输入为主;早中全新世气候湿润,风化作用显著增强,湖泊碎屑物质的流水输入过程增强;晚全新世流域降水量减少,植被有所退化,湖泊碎屑物质的风力输入过程增强,并伴随着百年至千年尺度的风沙活动事件.更尕海碎屑物质输入过程的变化可能响应于区域大气环流的变化.全新世早中期,强盛的亚洲夏季风可能是更尕海流域风化作用、流水输入增强的主要原因;而晚全新世频繁的风沙活动则可能与高纬地区千年尺度的气候冷事件有关.可见,亚洲季风与高纬冷气团（西风环流）的相互作用或许是我国亚洲季风边缘区气候环境变化的主要驱动因素.Understanding of the processes of detrital input to a lake is of great importance to investigate climatic and environmental changes in a region. The Gonghe Basin is located in the northeastern Qinghai-Tibetan Plateau, which is influenced climatically by both the Asian monsoon and the Westerlies. This area is crucial for understanding the climatic linkages between high latitudes and low latitudes in the Northern Hemisphere. Genggahai Lake （36°11＇N, 100°06＇E）, a small, shallow lake, is situated in the central of Gonghe Basin. Its water surface area is about 2km2, and the maximum water depth is about 1.8m. The simple hydrologic pattern and abundant biodiversity make it sensitive to the changing global climate system, and hence an ideal site to study environmental changes. Cores GGH-A （782cm in length; 36°11.42＇N, 100°06.23＇E） and GGH-C （774cm in length; 36°11.46＇N, 100°06.27＇E） were recovered at the water depth of 170cm in central Genggahai Lake. 12 samples of aquatic macrophyte remains were selected from core GGH-A for accelerator mass spectrometer （AMS） 14C dating. By comparing the varations of lithostratigraphical units and carbonate （Ca） content between cores GGH-A and GGH-C, we created an age-depth model of GGH-C. The age at the base of core GGH-C was 15.6cal.ka B.P. Chemical elements of core GGH-C were measured using high-resolution X-Ray Fluorescence （XRF） scanning. The abundances of Si, A1, K, Ti, Fe and Rb in sediments can be used as proxies for inputs of detrital material to the lake. Combined with the variability of sand processes of detrital material to Genggahai fraction （〉631xm） in core GGH-A, we reconstructed changes in input Lake and climatic changes in the study area since the Late Glacial. During the Late Glacial, the sediments was characterized by coarse median size and low content of Si, which indicated that a cold and arid climate prevailed. The input process of detritus was generally weak, and detrital material may have been transported mainly by

关 键 词：碎屑沉积 化学元素 粒度组成 输入过程 更尕海 

分 类 号：P534.632[天文地球—第四纪地质学] P941.78[天文地球—古生物学与地层学]