Keywords: 
• sequence stratigraphy /
• organic geochemical parameter /
• finegrained sediment /
• marl

Abstract: It is the key factor for establishment of scientific sequence stratigraphy framework to conduct sequence stratigraphic unit classification and correlation of deepwater fine sedimentary series. In addition, it is one important basic research for exploration and development of lithologic oil and gas reservoirs in deepwater areas. Its classification marker, which is usually indistinct, handicaps sequence stratigraphic unit correlation of deepwater fine sedimentary series and acts as one difficult point for sequence stratigraphy research. On the basis of high resolution sequence stratigraphy theory, this paper starts with origin and presence of sedimentary sequence and carries out sequence stratigraphic unit classification and correlation for semideep lake to deep lake marl deposit in lower Es3 of Jizhong depression in Shulu sag, Bohai Bay Basin by using periodical variation rules in vertical of organic geochemical parameters that present sedimentary environment or sediment characteristics. And consequently, cycle grade4 and grade5 are distinguished in a better way, which provides basis to establish highresolution sequence stratigraphy framework.