EVOLUTION OF BASIN BOTTOM MORPHOLOGY OF YANCHANG FORMATION,UPPERTRIASSIC,SOUTHWESTERN ORDOS BASIN

Southwest Ordos Basin has become a popular target in petroleum exploration and production,recently,which has plenty of petroleum resources,so a clear understanding of rules of basin bottom morphology is of greatsignificance in petroleum exploration. A study of stacking style of sandstones and migrating rules of deep lakeregion,together with,many event depositions show that the center of basin migrated from northeast to southwestalong with frequency earthquakes,lava,source uplift and front subside caused by Qinling orogenesis in period ofChang 7 Formation deposition. So,braided delta and turbidite formed in southwest basin because of asymmetricalbasin in which the south is steep and the north is slow. Basin bottom configuration changes from symmetrical toasymmetrical,and sedimentary facies changes from meandering delta to braided delta. At the same time,turbidite,tuff and sand dike are formed by Qinling orogenesis. Based on the evolution history of the lake basin bottom,theturbidite in Huachi,Qinchen and Zhenning area will be a potential petroleum exploring target.