青藏高原北部可可西里库赛湖沉积物及风成物的粒度特征

对青藏高原北部可可西里地区库赛湖钻孔沉积物、冰面风成物和流域风成物粒度特征进行了研究,结果表明: 库赛湖冰面风成物的粒度特征同流域风成物的粒度特征具有明显的区别,而钻孔沉积物的粒度分布特征却和流域风成物的粒度分布特征相似。对库赛湖钻孔沉积物端元组分的分析表明,库赛湖沉积物的来源主要有径流搬运、风力和冰川搬运组分构成,所占的平均比例分别为55.5 ％ ,35.9 ％ 和8.5 ％ 。库赛湖沉积物风成物端元组分的粒度分布特征,得到了冰面风成物粒度特征的验证。尽管没有获得径流搬运组分的样品,但钻孔沉积物的粒度分布特征同流域风成物的粒度分布特征具有的相似性,可能说明,由于库赛湖地区降水较少,湖区径流不发育,流域的风化作用很弱,流域风成物通过流水汇入径流,成为径流搬运的主要物质来源。

GRAIN SIZE DISTRIBUTION OF AEOLIAN AND LACUSTRINE SEDIMENTS OF KUSAI LAKE IN THE HOH XIL REGION OF THE NORTHERN QINGHAI-TIBETAN PLATEAU

Aeolian dust deposited on the ice covering Kusai Lake and in the lake catchment and the lacustrine sediments were analyzed for grain size distribution to investigate the proportion of different sources of clastic materials in the sediments of the lake, which will contribute to better understanding of the process of paleoenvironmental and paleoclimatic changes in the Hoh Xil region of the northern Qinghai-Tibetan Plateau.The data indicate that the grain size distribution of aeolian dust from the lake ice is quite different from that from the lake catchment,whereas lacustrine sediments display a similar distribution pattern to aeolian dust from the lake catchment.End-member modeling of grain size distributions of the lake sediments suggests that clastic deposits in the lake were transported by streams,wind and glaciers that brought 55.5 ％ ,35.9 ％ and 8.5 ％ of materials to the lake,respectively.The grain size distribution of aeolian end members generally matches that of aeolian dust collected in the lake area in winter.The similarity between grain size distributions of aeolian dust deposited in the lake catchment and the lake sediments might denote that the dust deposits had experienced fluvial retransportations under the condition of low precipitation and weak weathering in the lake region.