|关键词: 库赛湖 表面结构 石英颗粒 扫描电镜 风成沉积
|Surface textural analysis of quartz grains from varved sediments of Lake Kusai in the Hoh Xil area, Tibetan Plateau
CHEN Yu1,2, LIU Xingqi1,3,2
1.School of Resource Environment and Tourism College, Capital Normal University, Beijing 100048, P. R. China;2.State Key Laboratory of Lake Science and Environment, Nanjing 210008, P. R. China;3.Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, P. R. China
|Lake sediments containing aeolian deposits in the arid areas are one of the important archives for sedimentary studies. Surface textural analysis of quartz grains by scanning electron microscopy can provide an insight into the sedimentary history of clastic sediments, depositional environment and successive sedimentary cycles. Lake Kusai is located in almost uninhabited Hoh Xil region of the Northern Tibetan Plateau, and is one of the frequently dust storm-occurred areas occurring in Qinghai Province. In order to confirm the coarse grained layers formed by aeolian processes in varved sediments of Lake Kusai, 35 types of surface features of quartz grains are analyzed in different sediments, such as coarse grained layers in varved sediments of Lake Kusai, aeolian dune sediments, fluvial sediments, aeolian dust samples in the ice of Lake Kusai, lacustrine deposits in the lakeside. The results show that quartz grains in aeolian sediments have surface microtextures of rounded outline, low or medium relief, acuate steps, straight steps, crescent percussion marks, upturned plates, bulbous edges and dish-shaped depression, etc. The quartz grains in fluvial sediments have microtextures of angular or subangular outline, medium or high relief, V-shaped percussion cracks, small or medium conchoidal fractures, and solution pits, etc. The microtextures of quartz grains in the coarse-grained layers of varved sediments in Lake Kusai are rounded outline, low relief, acuate steps, straight steps, crescent percussion marks, upturned plates, bulbous edges, and dish-shaped depression, etc, which are similar to these of the aeolian sediments, but quite different from these of fluvial sediments. Thus, it is indicated that the coarse grained layers in varved sediments of Lake Kusai are formed by aeolian processes.
|Key words: Lake Kusai surface microtextures quartz grains scanning electron microscopy aeolian sediments