楼兰佛塔剖面10.84kaB.P.以来的环境变迁

ENVIRONMENTAL CHANGE OF THE PAST 10. 84ka IN LOULAN,XINJIANG

新疆楼兰佛塔剖面(40°30.980′N,89°54.849′E)深度6m,以5cm间距采样,共采121个样,进行了粒度、总碳、无机碳、有机碳、氮含量分析,根据光释光年龄结果内插得出剖面时间跨度为10.84～4.69kaB.P.,剖面气候环境可划分为3个阶段:10.84～10.13kaB.P.为高湖面湿润时期;10.13～7.45kaB.P.沉积间断,气候干旱;7.45～4.69kaB.P.罗布泊气候相对湿润,其间湖泊存在多次的收缩与扩张,湖面扩张是短时间快速完成的,湖面衰退是逐渐变化的。楼兰佛塔剖面顶部年龄为4.69kaB.P.,此区发现的石器基本为地表采集,年代不会早于4.69kaB.P.。

Lop Nur is the terminal lake of rivers in Tarim Basin where there are a few of records of Holocene environmental change. Unfortunately,their poorer temporal resolution has been a major obstacle to study Holocene climatic change,especially the climatic condition of mid-Holocene. Thus whether mid-Holocene was dry or humid remains an open issue. In this paper the Loulan tower section was selected to study the climate change of Early to Middle Holocene. This section（40°30. 980＇N,89°54. 849＇E）is located near a tower of Loulan,Xinjiang. It is 6m deep. There are 121 samples to be collected from it at the interval of5cm. Analyses of grain-size distribution,total carbon（TC） , total inorganic carbon （ TIC ）, organic carbon （ TOC ） , nitrogen （ N ） concentration were made for all samples. OSL dating was made for 4 samples of them. This section covered the interval of 10.84 - 4.69kaB. P. and can be divided into three stages： 10. 84 - 10. 13kaB. P., more humid; 10. 13 - 7.45kaB. P., no sediment and dry; and 7.45 - 4.69kaB. P., relatively humid. During the third stage of 7.45 - 4.69kaB. P., eorresponding to Middle Holoeene,Lop Nur had a high lake level,but was characterized by expanding rapidly in a short time and eontraeting gradually. The top of this section was of about 4.69ka. Stone artifacts found in this region was collected from ground surface,therefore their age is estimated to be younger than 4.69ka.