Sequence Straigraphy And Sedimentary Features Analysis Of Lacustrine Carbonate Rock In Upper 4^Th Member Of Shahejie Formation, Shaojia Area, Zhanhua Depression

This paper focus on sequence straigraphy and sedimentary features analysis of lacustrine carbonate rock in Upper 4th Member of Shahejie Formation, Shaojia Area, Zhanhua depression. Combine High-resolution Sequence Stratigraphy and modern sedimentology theory with core,geophysial logs and slice data analysis, identify lacustrine carbonate rock lithology,build up High-resolution Sequence Stratigraphy framework,and study the distribution characteristic of lacustrine carbonate depositional system. Finally, summarize depositional model and main control factors.Establish lacustrine carbonate column through Pingyi outcrop observation, column shows the fossil, lithology, sediment supply and vertical macroscopic style of lacustrine carbonate deposition. Sample geochemistry research indicate a shallow water, high salinity and closing lacustrine environment which can be used to support the research in Shaojia Area.The Upper 4th Member of Shahejie Formation in Shaojia Area is a third-order sequence, according to High-resolution Sequence Stratigraphy theory recognized three fourth-order sequence: C1, C2, C3. Sequence Stratigraphy division and correlation suggest that because of palaeogeomorphology and source systems, cycle preservation and composition are varied in different position of shaojia area. C3 cycle are poorly developed in the whole area, mostly develop in fan delta system of certain actic region, mainly preserved up hemicycle; C2 cycle is better developed, expect some high land areas of lake margin are dominated by erosion and only preserved up hemicycle. In C2 cycle, lacustrine carbonate are more developed in actic region while In gentle slope carbonate rock and clastic rock are mixed deposition; C1 cycle is best developed in shaojia area, owing to the compensating action of C3 and C2 cycle, carbonate rocks are widely developed in C1 cycle.Under the control of sequence straitigraphy, study depositional system distribution of lacustrine carbonate rock, result show that lake gemorphology, climate and material source play an important role in lacustrine carbonate deposition. In actic region, platform environment is common lacustrine carbonate facies including confine platform, platform algal mat, and platform algal reef. In gentle slope region recognized facies as followings: delt, mixed flat, mud flat, shallow algal mat.Through lacustrine carbonate lithology, sequence stratigraphy and sedimentary research, combined with lake geomorphology,tectonic and source analysis, establish sedimentary model of the Upper 4th Member of Shahejie Formation in Shaojia Area. Accomplish farther research on favorable carbonate reservoir model and predict potential reservoir.