The control role of stratigraphic sequence in diagenetic evolution in the terrestrial fault basin： a case study of Paleogene Shahejie Formation in Dongying half basin

Abstract：Based on stratigraphic sequence, thin-section analysis, SEM observation, vitrinite reflectance, X-ray diffraction and geochemical investigation, the authors systematically studied the relationship between the stratigraphic sequence and diagenesis. The results show that different stratigraphic sequence tracts have different diagenetic responses： crypto-crystal carbonate, anhydrite, iron pyrite are existent in the low tract; ferrous carbonate cementation and clay mineral cementation occur in the expanded tract; dolomite cementation, ferrous dolomite cementation, corrosion, clay mineral cementation exist in the high tract, and corrosion phenomenon and ferrous carbonate cementation are found near the stratigraphic sequence boundary. During the development of the stratigraphic sequence, the original fluid and the enrichment regularity of elements made up the main factors for generating the diagenetic response and affected the components of diagenesis. The control role of the stratigraphic sequence in diagenetic evolution finds expression in three aspects： a. The development of stratigraphic sequence controlled the original components of diagenesis and further controlled the reconstruction of late diagenesis. b. Early diagenesis had some response to the stratigraphic sequence development, whereas late diagenesis covered up most of the diagenestic response. c. Stratigraphic sequence boundary affected the diagenetic evolution by stream action, depositional interruption slowing down the compaction, and late fluid invasion.