东昆仑造山带东段下中三叠统研究进展

ADVANCES IN LOWER AND MIDDLE TRIASSIC STRATIGRAPHIC RESEARCH IN EAST OF EASTERN KUNLUN OROGENIC BELT

东昆仑造山带东段下中三叠统包括下三叠统洪水川群和中三叠统闹仓坚沟组 .根据实体化石和遗迹化石的研究 ,结合区域上的岩性对比 ,将洪水川群划分为 3个岩性单元 ,即底部砂砾岩段、中部灰岩夹砂岩段和上部砂板岩段 ,属于下三叠统印度阶和奥伦尼克阶 .闹仓坚沟组包括闹一段砂砾岩和闹二段砂板岩 ,从中三叠统早安尼锡期延续到中安尼锡期 .砂岩的常量元素分析结果表明 ,大部分砂岩为杂砂岩 ,属于复理石盆地的浊积岩范畴 ;砂岩稀土元素的特征值接近于活动大陆边缘和大陆岛弧元素的参数值 .

The Lower and Middle Triassic strata, east of Eastern Kunlun orogenic belt, contains the Lower Triassic Hongshuichuan Group and the Middle Triassic Naocangjiangou Formation. The studies of body and trace fossils, as well as those of the regional lithology correlation, show that the Lower Triassic Hongshuichuan Group included in the Lower Triassic Indian stage and Olenekian stage, are divided into three lithological units: the sandstone and conglomerate unit at the bottom, the limestone with sandstone unit in the middle, and the sandstone and slate unit at the top. The Naocangjiangou Formation ranging from the early Middle Traissic to Middle Anisian includes two members: the sandstone and conglomerate member at the bottom and the sandstone and slate member at the top. The analysis of constant elements in the sandstone indicates that the majority of sandstones are composed of greywacke, belonging to the turbidite in a flysch basin. The eigenvalues of the rare_earth elements in the sandstone are close to the parameters of the rare_earth elements located in the active continental margin and in the continental arc.