SUBDIVISION AND CORRELATION OF THE UPPER QILITAG GROUP (UPPER CAMBRIAN-MIDDLE ORDOVICIAN) OF TARIM BASIN,NORTHWEST CHINA

摘要

1 INTRODUCTIONThe Lower-Middle Ordovieian of the Tarim Basin,Northwest China,is dominated by a series of limestones and dolostones hundreds of meters thick,which was named as the Upper Qiulitag Group (Regional stratigraphic tables of Xinjiang Uygur Autonomous Region Writing Group,1981；Zhou et al.,1990；Zhang et al.,1991).This group is well exposed at Aksu and on the north slope of the Yingshan Mounmin,Wushi,and was subdivided into the Penglaiba Formation,Yingshan Formation and Dawangou Formation in ascending order by Zhou et al.(1991) (Text-fig.1).Zhao et al.(1997) and Zhou et al.(2001) followed this scheme.