西天山尼勒克北于赞一带下石炭统阿克沙克组扇三角洲相沉积的发现及意义  

Discovery of Fan Delta-Facies Sediment in Lower Carboniferous Akeshake Formation in the Yuzan Area,Western Tianshan Mountains and Its Significance

作　　者：李永军[1] 金朝[1] 胡克亮[2] 葛海影[1] 李鸿[2] 林列全[2] 

机构地区：[1]长安大学地球科学与资源学院,西部矿产资源与地质工程教育部重点实验室,西安710054 [2]新疆地质矿产勘查开发局地质九队,乌鲁木齐830000

出　　处：《地质学报》2010年第10期1470-1478,共9页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号40534020);新疆区域地质矿产调查项目(编号XJQDZ2003-24)资助成果

摘　　要：分布于新疆伊犁盆地北缘尼勒克北于赞一带的下石炭统阿克沙克组,下部为砾岩、砂砾岩、岩屑砂岩,厚度大于345m,属扇三角洲相;中部以生物碎屑灰岩、泥晶灰岩和鲕粒灰岩为主,夹钙泥质粉砂岩,富含早石炭世腕足、珊瑚、菊石、苔藓虫、层孔虫等多门类海相化石,厚182.97m,属滨海相浅滩亚相;上部为砾岩、含砾粗砂岩、岩屑砂岩等粗碎屑岩,厚度大于751m,海相腕足、珊瑚、菊石和陆相植物化石混生,属扇三角洲相。此次新确立的三角洲相建造与前人所述本组在伊宁地区均属浅海相沉积建造显著有别。结合区域资料证实,下石炭统在伊宁盆地南部为弧前深海半深海相沉积,在中部阿吾拉勒北坡为弧后浅海相沉积,而盆地北缘的于赞一带则为典型的扇三角洲相沉积,这一新发现对于重新认识伊宁盆地早石炭世古地理和古构造格局具有重要意义。The Lower Carboniferous Akeshake Formation in the Yuzan area,the northern margin of Yining basin,Xinjiang,can be divided into three main sections. The lower section consists of conglomerate,sandy conglomerate and lithic sandstone,with a thickness more than 345 m,which belongs to fan delta facies. The central section consists mainly of bioclastic limestone,micrite and oolitic limestone intercalated with relatively minor amounts of calcium argillaceous siltstone,and is enriched in various kinds of marine fossils of the Early Carboniferous,such as brachiopods,corals,ammonites,bryozoans,stromatoporoids,with a total thickness of 182.97 m,which belongs to shallow subfacies of littoral facies. The upper section is a succession of coarse-grained elastic rocks,which belong to fan delta facies and are composed of conglomerate,conglomeratic pebbly sandstone and lithic sandstone,with a thickness of more than 751 m,in which marine brachiopods,corals and ammonites coexist with terrestrial plant fossils. The newly defined delta-facies formation is significantly different from the shallow marine facies sedimentary formation defined in the Yining area by previous researchers. Combined with regional data,it is confirmed that the Lower Carboniferous is forearc abyssal-bathyal facies in the southern Yining basin and is back-arc shallow marine facies in the central part of Awulale Mountains. However,the Yuzan area in the northern margin of Yining basin is characterized by typical delta facies sedimentation. This new discovery is of significance for understanding paleogeography and paleotectonic pattern of the Yining basin in the Early Carboniferous.

关 键 词：阿克沙克组 扇三角洲相 尼勒克北 伊宁地块 西天山 

分 类 号：P512.2[天文地球—地质学]