The Prototype Basin During Es₄^x�Ek Period Of Yihezhuang�Bonan Area

Yihezhuang�Bonan area,located in the northeast of Jiyang depression,experienced a complicated tectonic evolution process during the Mesozoic and Cenozoic.Based on the construction interpretation of 3D seismic data,drilling and logging data,this paper analyzed the residual strata distribution of Es₄^x�Ek formation of Yihezhuang�Bonan area,and had a detailed depiction for the static characteristics of fault system to make clear to distribution characteristics of the fault system;through fault activity,balanced-section profile,stretching rate and regional dynamics background analysis,this paper found out the evolution process;what's more,this paper restored the exhumation and original thickness of Es₄^x�Ek formation to make clear to the prototype basin in the period of Es₄^x�Ek of Yihezhuang�Bonan area.The formation of Es₄^x�Ek can be divided into three sub-layers,Ek₂,Ek₁,Es₄^x.The distribution of the residual strata was uneven and was in the NW direction.However,the formation of Es₄^x showed a trend of NE distribution.There mainly were three directions of the fault in the period of Es₄^x�Ek,NW,NE EW.The faults of NW and NE direction intersected,forming the tectonic pattern.The superposition transformation of faults near EW and NS direction made further complicated fault system.Fault assemblages on the plane are oblique,gridded and parallel in arrangement.On the profile,the structural style was complicated and the stench structural style was mostly developed and there were some extensional strike slip structural style in the northeast of Yihezhuang�Bonan area.The period of Es₄^x�Ek was in the period of basin transformation,and the process of tectonic evolution was more complicated.The fault activities in different evolution stages and different directions were different:the Kongdian formation was mainly dominated by NW trending faults,and the North East fault in the four member of the lower part of the sand was active,which controled the evolution of the basin with the NW trending faults.The surrounding areas,such as Yihezhuang uplift,Chenjiazhuang uplift,Chengdong uplift and Gudao uplift,were formed before the period of Es₄^x�Ek,and they provide sediment source for the formation of Es₄^x�Ek.The prototype basin in the period of Ek of Yihezhuang�Bonan area was the rift basin with a fault in the northwest and an overlap in the southeast,the prototype basin in the period of Ek was controlled by the NW trending faults singly and the prototype basin in the period of Es₄^x was controlled by NW and NE trending faults together.After the period of Es₄^x�Ek,the basin suffered intense erosion and changed,forming the present alternately upwarped and downwarped tectonic framework.