Paleogene sequence stratigraphic framework and model in the Huanghua depression

Sequence stratigraphy has developed for over 40 years,but it was applied to continental basins in China only ten years ago.The integrated sequence stratigraphic framework for the entire stratigraphic succession has not been established in many basins such as the Huanghua depression.Based on previous research,proceeding from the principle of sequence division and through studies of the characteristics and identification indicators of different orders of sequences and system tract boundaries,the paper proposes a scheme of sequence division in the Huangliua depression and divides the Paleogene strata into 1 first-order sequence,3 second-order sequences and 11 third-order sequences.Based on studies of typical sections,the authors propose that the abrupt change of the depositional slopes,resulting from the structural slope break zone or flexure slope break zone,has an important effect on the accommodation and sedimentation in the basin and that the structural slope break zone and flexure slope break zone control the development of the sequences and lowstand sand bodies.Two models for the relation between slope break zones and sequences have been constructed,and it is pointed out that the areas below the slope break zones are favorable zones for the deposition of lowstand sand bodies.