Stratigraphic Classification and Correlation of Cambrian in Bachu Uplift,Tarim Basin

The Cambrian rocks commonly occured in the wells of Buchu uplift in Tarim basin could be divided into three series and seven members.They are clastic member,dolomite member and gypsum-bearing dolomite member in the lower series;subsalt carbonatite member,gypsum-salt member and gypsum-bearing dolomite member in the middle series,and pure dolomite member in the upper series,based on their obviously different electrical properties.The abundance fossils of small shell and algae found in the clastic member are discussed in space-time distribution in detail,and the age of the strata with small shell is determined as the early of Early Cambrian in wells of Bachu uplift.The outcrop section correlation shows that the clastic member and Yurtus formation belong to the relation of the same age but different facies.The subsalt carbonatite member corresponds to Shaylik formation,which can be considered as marker bed for formation correlation in this area.In addition,according to seismic sequence stratigraphy,the Cambrian strata can be divided into three super-sequences which correspond to three series;in terms of drilling sequence stratigraphy,it can be two and half super-sequences and five sequences.The classification and the correlation of the Cambrian strata in this area establish a stable stratigraphic foundation for further studies related to Bachu uplift.