Genetic research of flaggy lacustrine carbonate in the first Member of Shahejie Formation, Dongying Depression

Key words:  Dongying Depression  lacustrine carbonate  sedimentary genesis  algal reef  sedimentary evolution

Abstract:

This study focused on the flaggy lacustrine carbonate reservoir in the first Member of Shahejie Formation of the HB area in Dongying Depression. The analysis of the carbonate genesis is through a combination of core observation, thin section and paleontology identification, integration of lithofacies, logging facies, and geochemical characteristics. The results show that the carbonate can be divided into early-stage, mid-stage and late-stage sedimentary bodies. The mid-stage sedimentary body, constituting the principal part of the carbonate, can be further subdivided into the algal frame reef, inter-reef, reef-front, back-reef, continental sandbar and mudflat genetic elements. The suitable environment, resulting from changes of climatic and hydrological conditions, contributes to the flourishment of the algal reef. Because of the transgression in the late depositional stage, the euryhaline snails and ostracoda thrive and widespread snail limestone develops in the late-term sedimentary body, leading to the finality of the algal reef.