阿尔金山北麓米兰河口新近纪以来碎屑沉积特征及其构造意义

通过对阿尔金山北麓新疆若羌米兰河口剖面新近纪沉积序列的详细研究,结合区域资料,将该区地层由下至上划分为中新世乌恰群、晚中新世-早上新世的阿图什组、晚上新世西域砾岩组和早更新世乌苏群。根据岩性、沉积物粒度、沉积结构和构造以及地层几何形态特点,新近纪以来该区沉积环境经历了从中新世湖相沉积到晚中新世-早上新世扇三角洲沉积,再到晚上新世洪积扇沉积,最后至第四纪洪积扇和河流沉积的演化。结合剖面向上阶段性变粗、砾岩增多变厚、砾石成份中深变质岩和火成岩含量增加以及古水流也呈有规律变化等特征,可推测自新近纪以来阿尔金山至少经历了晚中新世-早上新世、晚上新世、早更新世和中更新世以来4个阶段的重大构造隆升过程,并且后3次构造活动幅度较前一次强烈。

Sedimentattion Characteristics of Clastic Rocks in the Neogene Milan River Mouth along the Northern Margin of Altun Tagh Mountain and Their Tectonic Significance

The late Cenozoic sediments are grown in the northern piedmont of Altun Tagh range hinted the signals of strike-slip faults along Altun Tagh Fault Belt and the information is about the mountain surface uplift and erosion history. While the characteristics of sediments is rarely known. Milan River section,in Ruoqiang,Xijiang,is located in the northern margin of the Altun Tagh mountain. The section of 980m thick represents the upper sequence of the Cenozoic basin sediments. Based on the field measurements and laboratory analyses of the sedimentary characteristics,it can be divided into four parts from bottom to top:the first is lacustrine(Wuqia Group),the second part is fan-delta(Artux Formation) and the third and forth parts are fluvial(Xiyu Formation and Wusu Group). They belong to the Miocene,Late-Miocene,Pliocene and Pleistocene,respectively. Altun Tagh Mountain might undergo four stages tectonic uplift,and they took place in Miocene,Late-Miocene,Plioc ene and Pleistocene,and the latter three tectonic uplift activities are much more intense than the first one.