塔里木盆地草湖凹陷白垩纪湖相地层

CRETACEOUS LACUSTRINE STRATA IN THE CAOHU SAG,TARIM BASIN,NW CHINA

塔里木盆地草湖凹陷白垩系皆分布于井下,以陆相沉积为主,下统自下而上为亚格列木组、舒善河组、巴西盖组与巴什基奇克组;首次发现上白垩统并命名为古城墟组。这套湖相地层中化石稀少,仅舒善河组中可划分出介形类Minheella-Damonella-Darwinula组合带,孢粉Classopollis-Lygodiumsporites-Schizaeosporites组合带和Dicheiropollis-Classopollis-Lygodiumsporites组合带。草湖凹陷白垩系以满2井序列最齐全且各单元岩电识别特征明显,可划分为3个Ⅱ级层序和6个Ⅲ级层序,湖盆沉积区的扩展以及各组横向分布明显的时空差异性强烈受燕山晚期构造运动的控制。

The Cretaceous lacustrine sequence in the Caohu Sag,Tarim Basin is investigated from drill cores.It could be subdivided into the Lower Cretaceous Yageliemu,Shushanhe,Baxigai and Bashijiqike formations and the Upper Cretaceous Guchengxu Formation.Of these,the Guchengxu Formation is established for the first time.More detailed biostratigraphic study is focused on fossiliferous intervals.Only the ostracod Minheella-Damonella-Darwinula biozone and the sporopollen Classopollis-LygodiumsporitesSchizaeosporites and Dicheiropollis-Classopollis-Lygodiumsporites biozones are recognized from the Shushanhe Formation.The most complete lithostratigraphic sequence occurs in the Well Man 2,which consists of three second-order and six third-order sequences.The Man 2sequence can serve as a regional lithostratigraphic standard.The distribution and sedimentary pattern of Cretaceous lacustrine facies is controlled by the late Yanshan Orogeny.