西天山伊犁地区上、下石炭统接触关系的重新厘定及其构造意义——来自沉积学和岩相学的证据

摘要

西天山上、下石炭统之间是否存在区域性角度不整合争议颇大,制约了西天山晚古生代构造演化阶段的划分.伊犁地区石炭纪地层出露典型且完好,通过对该地区上、下石炭统接触关系的重新厘定,开展沉积学和岩相学研究.沉积学特征显示,二者产状一致,未见底砾岩和风化壳,且存在碳酸盐岩和火山碎屑物质"混生"的沉积特征,下石炭统阿克沙克组和上石炭统伊什基里克组之间并无明显沉积间断,应为连续的火山–沉积序列.该研究为西天山伊犁地区石炭纪为统一后碰撞裂谷盆地的认识提供了沉积学证据.%It is quite controversial whether there is a regional angular unconformity between the Upper and Lower Carboniferous strata in Western Tianshan Mountains,and such a situation restricts the division of the Late Paleozoic tectonic evolution.The Carbon-iferous strata are typical and intact in Yili.In this paper,the sedimentary and petrographic studies were carried out by redefining the contact relationship between the Upper and Lower Carboniferous strata in this area.The sedimentary characteristics show that these two strata are consistent,without conglomerate and weathering crust,and are characterized by mixed carbonate and volcanic debris. The Lower Carboniferous Akeshake Formation and Upper Carboniferous Yishijilike Formation may have no significant depositional interruption, and should be a continuous volcanic-sedimentary sequence. This study provides sedimentary evidence for the under-standing of the Carboniferous as a unified post-collision rift basin in the Yili area,Western Tianshan Mountains.