Abstract:

After analyzing the stratum and lithological character of the Lower Tertiary of the south of the Chengbei sag to the west of the Zhuangdong sag，Bohai Bay basin，using the knowledge of biologic stratigraphy，lithologic stratigraphy and sequence stratigraphy，we study the palaeoenvironmental setting of the study area on the base of changing of palaeoclimate and tectonic movement. This paper comprehensively summarizes the sedimentary system types and evolutive character of the Lower Tertiary faulted basin in Chengbei sag，then studies the main dominant factors of evolvement of the sedimentary system and sequence，and divides Lower Tertiary into three sequences, including Kongdian Formation to lower Shasi subformation，upper Shasi subformation to lower Shaer subformation，and upper Shaer subformation to Dongying Formation. The main dominative factors of the evolvement of the sedimentary system and sequence include the movement of structure，the change of climate and the filling of sediments.

Key words: Bohai Bay basin, Chengbei sag, Zhuangdong sag, stratum, sedimentary system, sequence