Sequence stratigraphy of the Paleogene Shahejie Formation in Dongpu Sag,Bohai Bay Basin

Based on stratigraphical correlation of over 300 wells,detailed core description of more than 3 000 m,and analysis of regional tectonic-sedimentary evolution,we divided the Paleogene in Dongpu Sag into three super long-term sequences according to various data such as tectonic geology,paleontology,lithology,geochronology,logging and seismic reflection,etc.The three sequences corresponds to the lower 4th member of Shahejie Formation,the upper 4th member to the 3rd member of the Shahejie Formation,the 2nd member of Shahejie Formation to the Dongying Formation respectively.Furthermore,strata from the upper 4th member to the 1st member of Sh-ahejie Formation is divided into four long-term sequences,corresponding to the upper 4th member to the 4th sub-member of the 3rd member,the 3rd sub-member of the 3rd member,the 1st to the 2nd sub-member of the 3rd member and the 1st to the 2nd member of Shahejie Formation respectively.This paper indicates that a set of continuous salt deposits is undividable when dividing the super long-term and long-term sequence.Taking the Dongpu Sag and Bohai Bay Basin as examples,we pointed that the common practice of making sequence stratigraphic class-ification scheme consistent with lithostratigraphic classification scheme is possibly incorrect.