羌塘盆地东部冬曲地区上三叠统巴贡组主要发育暗色细粒碎屑岩沉积.冬曲野外露头剖面巴贡组碎屑岩的岩性特征、沉积构造、概率累积曲线、粒度参数和C-M图等的分析结果表明:冬曲地区巴贡组砂岩总体较细,分选较差,概率累积曲线主要为"一段式",悬浮总体含量较高,跳跃总体和滚动总体较少;在C-M图上表现为与C=M基线平行的直线段;沉积构造发育深海—半深海复理石标志性的Paleodictyon古网迹遗迹化石.综合研究认为冬曲地区巴贡组为一套典型的远源滑塌浊积岩沉积.结合邻区巴贡组沉积特征,推测羌塘盆地晚三叠世具有多岛海的古地理格局.

The Upper Triassic Bagong Formation in Dongqu area of the eastern Qiangtang Basin is mainly composed of dark fine clastic rock. The lithologic characters, sedimentary structures, probability cumulative grain size curves, grain-size parameters and C-M pattern of the sandstones of Bagong Formation in Dongqu outcrop profile all show as follows: the sandstones is generally fine and poorly sorted, the probability cumulative curve of the sandstones mostly represents one-stage, with a high percentage of the suspension and low percentage of the traction and saltation. In the C-M diagram, a line segment parallel to the C=M baseline is represented. The sedimentary structure of Paleodictyon trace fossils, which is flysch marks of deep sea-moderate sea, developed in Bagong Formation. Based on the comprehensive analysis, it is concluded that the Bagong Formation is a typical set of far-source fluxoturbidite in Dongqu area. Combined with the depositional characteristics of Bagong Formation in adjacent area, it is inferred that a palaeogeographic pattern of archipelago in Late Triassic developed in Qiangtang Basin.