Diagenesis within the sequence stratigraphic framework in the ramp zone of the half-graben fault lake basin:An example from the Shahejie Formation in the southern ramp zone of the Dongying depression,Shandong

The Dongying depression was once a half-graben fault lake basin being steep in the north and gentle in the south during the deposition of the Shahejie Formation.The studies of cores,well logs,thin sections and SEM result in the recognition of the alluvial fan,river,delta,littoral and shallow lacustrine sandbar,distal turbidite fan and lacustrine depositional systems in the Palaeogene Shahejie Formation in the southern ramp zone of the Dongying depression,and construction of the sequence stratigraphic framework and its evolutionary model for the southern ramp zone of the Dongying depression.The emphasis is laid on the diagenesis within the sequence stratigraphic framework,including compaction,pressure solution and dissolution.The diagenetic stages contain Stages A and B of the early diagenesis,and Stages A and B of the late diagenesis.The diagenetic facies consist of carbonate cementation quartz,secondary enlargement,kaolinite cementation and mudstone compaction diagenetic facies.