The Evolution Of Yingkou-Weifang Fault Zone And Its Control On Tectonic Framework Of Adjacent Basins

Tan-lu fault zone is one huge strike-slip fault zone which lies in eastern china and Yingkou-Weifang fault zone only means Yingkou to Weifang zone. Following predecessor's research and basing on lots of geophysical information(gravity,magnetism,electricity,earthquake),geotraverse and MT analysis, I researched the basic characters and distribution of Yingkou-Weifang fault zone. Basing on studying predecessor's research, I summarized the evolution and dynamical background of Yingkou-Weifang fault zone. According the research result, I found that the growth of Yingkou-Weifang fault zone is stepwise and multiphase. I divided the evolument of Yingkou-Weifang fault zone into seven steps as follows:â‘ compression during early-middle Jurassic;â‘¡the left-lateral strike-slip from late Jurassic to early Cretaceous, this step mainly occurred in Weifang-Laizhouwan-Huanghekou zone and Liaodongwan south zone, and seldom in Bozhong zone;â‘¢l eft lateral compression in late Cretaceous;â‘£the left-lateral strike-slip and extension from Palaeocene to early Eocene, the step mainly occurred in Weifang-Laizhouwan-Huanghekou zone, but seldom in Bozhong and Liaodongwan zone;⑤the extension and the right lateral strike-slip during middle Eocene, this step mainly occurred in north Liaodongwan and Bozhong zones;â‘¥the right lateral strike-slip during Oligocene, this step mainly occurred in Bozhong and Liaodongwan zones,and seldom in Weifang-Laizhouwan-Huanghekou zones, tenso-shear represented Liaodongwan north zone , compression shear which made Liaodong zone heave and run through represented Liaodongwan south zone, compression shear represented Laizhouwan sunken eastern fault zone;⑦the weak compression and right lateral strike-slip form Tertiary to now.According to the unconfromitis, layers above Jurassic can be divided into nine structral sub-layers: J₁₊₂, J₃+K₁, K₂, Ek+Es₄, Es₃, Es₂+Es₁, Ed, Ng+Nm, Qp. Then the characteristics of the lithology and the distribution were ascertained. Through the division and comparison on the evolution of structral layers, the area of research can be divided into nine periods: J₁₊₂, J₃+K₁, K₂, Ek+Es₄, Es₃, Es₂+Es₁, Ed, Ng+Nm, Qp form Jurassic to now. Depression jiyangensis and basin jiaolaiensis are basins which are the neighbors of Yingkou-Weifang fault zone. Their coming into being and evolution have quite a lot relationship with Yingkou-Weifang fault zone. In this paper, I did balanced section analysis on 16 seismic lines, and then calculated on extension amounts and rates of every section in different geologic time. At the same time, I protracted structural subsidence curves on selected 18 wells and calculated tectonic subsidence speed. The focal content of this paper analysed the diffirence of extension rates tectonic subsidence speed in different geologic time when they were in the same area and in different areas when they were in the same geologic time. Finally, I summed up the frontal research and adequately discussed how Yingkou-Weifang fault zone have effected on the structures framework of its adjacent basin.â‘ Late Triassic- Early-Middle Jurassic, Indo-Chinese Epoch(T3)Yangzi plate and Huabei plate hit and pieced together, at this time, Huabei plate was surrounded by Yangzi plate and Sibirica plate, under the level extrusion of SSW-NNE and shear structure of Tan-lu fault zone's left lateral strike-slip, Yangzi plate was lifted up and caused denudation of late-middle Triassic, at the same time, the plate adjusted itself and produced partly thrust fault.â‘¡Late Jura - Early Crataceous, Yingkou-Weifang fault zone left lateral strike-slipped. At the west side of it, 3 grabens grew from north to south. Jiyang down warp was in left lateral shear stress field which was made by Yingkou-Weifang fault zone and Cangdong-Lanliao fault zone, spread by SW-NE, its construct was reversed. Because of Yingkou-Weifang fault zone's left lateral strike-slip and Wurong fault zone's right lateral stike-slip, Jiaolai zone was pulled towards north east.â‘¢Late-Cret, Pacific converged at the speed of 130mm/year,which made compressional structure stress field at the east of China. Bohaiwan basin was lifted entirely. Yingkou-Weifang fault zone and Moping-Jimo fault zone right lateral strike slip made Jiaolai basin was pulled by two forces which came from south and north. In the basin;â‘£Palaeocene-Early Eocene, under the function of left lateral stress field which was produced by Yingkou-Weifang fault zone's left lateral strike-slip, downslip fault grabin or half grabin basin were formed in Jiyang-Changwei and Luxinan zone by NW direction. From the last stag of Early-Eocene to the early stage of Middle-Eocene, Yingkou-Weifang fault zone and its west zone's structure changed, as Yingkou-Weifang fault zone changed left lateral strike-slip to right lateral strike-slip. The stress filed of Jiyang sunken changed its direction from NW to SN. At this period, NW and NE fault both grew, but NW fault gradually disappeared after Shasi-Kongdian segment's peak development stage. Reversely;⑤Middle Eocene-Oligocene, Yingkou-Weifang fault zone show right lateral strike-slip and extension. At the period, basing on strike-slip, NW-NW fault was produced and extended from south to north. This period was the main extension stage of Jiyang sunken and NE fault's activity reached the peak.â‘¥Late Tertiary Period- Quaternary Period, because Pacific plate speeded up to under thrust East Asia mainland, strike-slip fault zone was still active in Bohaiwan basin. Extension became weaker, the basin heat sank and came into down warp stage.