风成沉积物粒度特征及其反映的青海湖周边近32 ka以来土地沙漠化演变过程

 湖东地区是青海湖周边土地沙漠化面积最大、程度最为严重的区域。选取青海湖湖东种羊场附近高度约为10 m的风蚀残丘（大水溏剖面）为研究对象,结合高密度采样和光释光测年,在对风成沉积物的粒度组成、粒度参数及粒度敏感指标进行分析的基础上,重建了32 ka以来青海湖周边的土地沙漠化演变过程。结果表明,32 ka BP以来青海湖周边土地沙漠化经历了末次冰期间冰阶（32～23.4 ka BP）的固结成壤期、末次冰期冰盛期（23.4～15 ka BP）的快速扩张期、末次冰期冰消期（15～10.4 ka BP）的缓慢减小期和全新世（10.4 ka BP至今）的快速缩小期4个阶段。

Evolution Process of Land Desertification around Qinghai Lake since 32 ka BP Reflected by Sediment Grain-size Features

Land desertification in the east coast is the most serious and has the largest area among areas around the Qinghai Lake. In this paper we took an aeolian sediment section at Dashuitang (QDST section) in the east coast of the Qinghai Lake as the research object to reconstruct the evolution process of land desertification around Qinghai Lake during the last 32 ka by the environment evolution information extracted from grain size composition, grain size parameters and grain size sensitive index. Results show that the evolution process of land desertification in the study area can be divided into four stages since 32 ka BP. In the interglacial period of the Last Glacial Stage from 32 ka BP to 23.4 ka BP, the climate was humid with weak wind, and sand dunes experienced being fixed and pedogenic process. So the area of land desertification land during this period was the smallest. From 23.4 ka BP to 15.2 ka BP, the climate was cold-dry with strong wind, and the intense aeolian activities activated sand dunes. Land desertification area during this period was the biggest in the past 32 ka. In 15~10.4 ka BP, land desertification area slowly decreased under the background of increasing temperature and humidity. Since 10.4 ka BP, aeolian activities weakened with the climate changed from cool-dry to wet-warm, sand dunes were fixed and consolidated into soil, and the land desertification area significantly decreased.