Stuctral-sedimentary Synthetic Method Ofr Restoring Denuded Thickness

It's a tough problem to calculate denuded thickness accurately. In order to restore the exact denuded thickness of the fourth member of the Shahejie formation of Jiyang depression, considering the geological characteristics of this area, firstly we establish a geological model of the erosion area for different composite units of this area, analyze the dynamic characteristics and erosion types. Secondly, according to the tectonic evolution features, we analyze the relationship between the thickness of sediment and erosion, then we use the balance sections to determine whether there are erosions and the scope of erosions, finally we calculate the approximate values of the denuded thickness in the areas where there are erosions.Finally, for different composite units of this area, we distinguish three zones, such as raised area, sag area and transition zones, then use deposition rate method, porosity optimization method, interval transit time method and vitrinite reflectance rate method to calculate exact values of the erosion thickness. In the flexible use of the above methods at the same time, referring the results of the geological depositional history and tectonic evolution, we obtain the final thickness of eroded strata by integrating weighted average and ensure the accurateness of the erosion thickness.The results show that:in the whole range of Jiyang depression, there is erosion in most parts of the fourth member of the Shahejie formation. Huimin sag is greater than the erosion of Dongying sag, Maximum erosion area is located in the edge of the south slope and the central uplift belt, erosion thickness exceeds 500m, while erosion thickness in the subsag is hardly denuded, such as the depocenter of Yangxin subsag, Zizhen subsag and Linnan subsag never denuded; The largest erosion region in Dongying sag is located in the edge of the south gentle slope and the north steep slope belt, The total erosion thickness is about200～300m, While erosion thickness are relatively small in the center of Minfeng subsag, Lijin subsag, Boxing subsag; The largest erosion area of Chezhen sag is located in the Taoer River nose structure belt and Dawang nose structure belt, The total erosion thickness is about200～300m, While the erosion thickness are relatively small in the Chexi subsag ,Da Wangbei subsag and Guo Juzi subsag; Zhanhua sag is eroded more uniformly, denudation at between 200 ~ 300m.