青藏高原南部邛多江盆地新建更新统洛村组地层特征及意义

The Luocun Formation,a newly established Pleistocene stratigraphic unit in Qiongduojiang basin,southern Tibet

错那-沃卡裂谷是青藏高原南部的众多新生代南北向裂谷之一,该裂谷中段的邱多江盆地沉积了大面积的第四纪湖相沉积物。此前由于地质调查程度较低,古湖积物的地表调查工作基本属于空白。本次调查对洛村-邛多江盆地古湖积物进行了详细研究,在洛村地区发现了完整的古湖积物的连续沉积,测制了地层剖面,开展了精确的光释光定年分析,结果显示其沉积时代为上更新世。鉴于区域上该套更新世地层出露面积广、厚度大,故新建地层单元,定名为洛村组(Qp 3 lc);并推测邱多江-洛村古湖可能是雅鲁藏布江中部超大古堰塞湖的一部分,洛村组是由藏南地区错那-沃卡裂谷和古大湖共同作用形成,初步计算了古湖出水口、湖面高度、湖水面积等参数。

Though out detailed geological mapping,profiles’measuring,and optical stimulated luminescence dating,we named a new Pleistocene stratigraphic unit Formation,the Luocun Formation in the Qiongduojiang basin,southern Tibet.The Luocun Formation is mainly composed of lacustrine deposits such as clay,sand and gravel.It was a product of the paleo Yarlung Zangbo Jiang lake which was formed by the clogged Yarlung Zangbo River from 0.025Ma to 0.078Ma.During that time,the Luocun basin,in which the Luocun Formation occurred,was a part of the Yarlung Zangbo paleo-lake caused by activities of glacier and geological slides in the studied areas.Parameters such as its outlet,height,and lake surface of the Yarlung Zangbo paleo-lake are also preliminarily calculated in this paper.