青海湖地区晚第四纪黄土的物质来源

青海湖地区的晚第四纪黄土记录了湖区晚第四纪以来的环境和气候变化.迄今为止，对于青海湖地区晚第四纪黄土物质来源的研究较薄弱.以青海湖东岸的种羊场晚第四纪风成沉积剖面为主要研究对象，在青海湖区及其周边采集了黄土、风成砂、湖相沉积、河流沉积等样品，结合黄土高原西部临洮黄土样品，对它们的元素组成(＜75 μm的硅酸盐组分)进行了对比研究.初步结果表明:(1) K₂O/Al₂O₃(摩尔比)和Zr/Ti、Zr/Nb比值显示青海湖地区的风成沉积显著区别于本区的河流沉积和湖相沉积；(2) 青海湖地区的晚第四纪黄土与黄土高原西部临洮黄土的K₂O/Al₂O₃和Zr/Ti、Zr/Nb比值相一致；(3) 青海湖地区的晚第四纪黄土可能来自柴达木盆地. 

Provenance of the Late Quaternary Loess Deposit in the Qinghai Lake Region

Late Quaternary loess deposit is widely distributed in the Qinghai Lake region and adjacent area. The loess deposit independently recorded the environmental and climatic changes during the late Quaternary in the Qinghai Lake region, northeastern Qinghai-Tibetan Plateau. Nearly all studies are focused on reconstructing the environmental and climatic changes recorded by loess deposit in the Qinghai Lake region. However, up to now, the provenance of the loess deposit in the Qinghai Lake region is still poorly understood. Here we present the elemental concentration of the silicate fraction of the eolian deposit ( < 75 μm) from the ZYC section in the Qinghai Lake region and LT section at Lintao County on the western Chinese Loess Plateau, loess deposits at Guanjiaoshan Mountain, Chaka town and Wulan County, eolian sands at western and eastern shore of the Qinghai Lake, and fluvial deposits from the Buhahe river and lacustrine deposits at Erlangjian site in the Qinghai Lake region. The results show that: (1) K₂O/Al₂O₃ (molar ratio) and Zr/Ti, Zr/Nb ratios indicate that the eolian deposits in the Qinghai Lake region and adjacent area can be distinguished clearly from the local deposits represented by river deposits at Buhahe river and lacustrine deposits at Erlangjian in the drainage basin of Qinghai Lake; (2) There is similarity of the elemental ratios (K₂O/Al₂O₃ and Zr/Ti, Zr/Nb) between the eolian deposits in the Qinghai Lake region and loess deposits at Lintao County. Thus, the eolian deposits in the Qinghai Lake region and Lintao County may have the same source region; (3) Late Quaternary loess deposit in the Qinghai Lake region is probably sourced from the Qaidam basin.