The Palaeogeomorphologic Reconstruction Of Es2 In Zhuangxi Area, Bohai Bay Basin

The Zhuangxi area is a sub-tectonic-unit in Zhanhua Sag, Jiyang depression, Bohai bay basin, and located in the northeast of Zhanhua Sag. There is Chengdong uplift in the west, Chengbei low-uplift in the north, Wuhaozhuang uplift in the east, and the sediment is controlled by the Chengdong uplift, Chengbei low-uplift and the boundary faults. The paper is mainly to reconstruct the palaeogeomorphology of Es2 in the Zhuangxi area.Palaeogeomorphology is a main factor to control the development and distributing of the sedimentary facies like the geomorphology today which is affected by the factors such as the location of the area tectonics, weather, the change of the datum plane and the tectonics movements. The characteristic of Es2 sediment in the Zhuangxi area is to controlled by the palaeogeomorphology before deposited. So, it is very significant to reconstruct the palaeogeomorphology of Es2 in the regions of Zhuangxi. This paper gets research from compaction, denudation, and reconstructs the palaeogeomorphology of Es2 in the Zhuangxi area.The hypothesis to reconstruct in this paper is that the change of the original sedimentary thickness(uncompacted thickness) can fix on the character of the palaeogeomorphology when the deposition is over. So, when the palaeogeomorpholo- gy is reconstructed, there are several problems such as restoration of eroded thickness, compaction adjusting and paleobathymetry.This paper has gotten these conclusions: there are many synsedimentary and deposit faults, and these faults control the Es2 sediments in the Zhuangxi area. In the area, the remained sediments of Es2 mainly distribute in the east of the Chengdong fault, in the west of Changdi fault and in the south of Gubei fault, there is no sediment in the Zhuangxi buried hill in the middle. A stratum true thickness isoline map has been made with the emendation of the true stratum thickness. After several methods to restoration of eroded thickness are adopted, the erosion mainly is in the west, secondly in the east, in the south, and the most eroded thickness is 30m. This paper has restored the original stratum thickness after the compaction emendation, and reconstructed the paleobathymetry of the area which has up lands and down lands, and discussed the relationship between the paleobathymetry and the sedimentary facies, and the paleo-slope area is propitious to the development of the sand bars. After the restoration of the tectonics, we can find that the Zhuangxi area is extending, and the sedimentation centre is displacing to southeast.