The Feature Of Basement Fault Complex And Its Effect On Cap Rock Deformation In The Lufeng Sag

Lufeng Sag is a secondary structural unit in Zhu?depression,Pearl River Mouth Basin,with an area of about 4500km~2.In recent years,there have been several sets of Wenchang reservoirs in the LF13 tectonic belt in the southern area of??the Lufeng Sag,Pearl River Mouth Basin,revealing the great exploration potential of the Lufeng Sag.However,at present,it is difficult to study the tectonic evolution stage and evolution model of Lufeng area,and it is difficult to meet the prospect of further exploration.Based on the interpretation of three-dimensional seismic data,the paper analyzes the distribution characteristics and distribution of fault plane,studies the combined relationship of faults in section,and studies the control effect of basement fault on cap rock deformation in combination with analogue modelling.The LF7-9 Uplift is located in the southern area of??Lufeng Sag,which is an anticline structure of Lufeng 13 East fault.Through the analogue modelling,it is considered that the boundary fault of Lufeng 13 Dongwa depression is a kind of large-scale"rolling anticline"",which is caused by the gravitational wrinkles caused by gravity,rather than the anticline structure formed by the arching of the bottom material.The combination of the two boundary faults in the low rise of Lufeng has also changed with the change of the width.In the middle of Lufeng in the east,the width of the larger,two faults were"into"the font,in the middle of the low peak in Lufeng,two faults were"X"type,with the width further reduced,in the Lufeng low in the west,two faults were"people"type combination of style.The difference of tectonic pattern is related to the fault activity.If the fault is active on both sides,the"X"type is formed..If the right fault is active firstly with the left side active latter,”into”type faults may form,vice verse,faults show in"people"type.Through analogue modelling,it is considered that the fault activity on both sidesare different,leading to the difference of fault combination pattern.There are significant differences in the tectonic-sedimentary evolution of the Paleogene in Lufeng Sag,which is mainly manifested in:first,the sedimentation center is characterized by migrating from south to north.During the deposition period of the Wenchang Formation,the subsidence rate of the depression is Luwa 15 depression,Lufeng 13 Dongwa>Lufeng 13 Xiwa,Lufeng 7 depression>Huizhou 11 depression,Huizhou 5 depression;Enpingformation deposition period,the subsidence rate of subsidence is Huizhou 11 depression,Huizhou 5 depression>Lufeng 13 West depression,Lufeng 7 depression Lufeng 15 depression,Lu Feng 13 East depression.Second,the rift effectstarts in southern area and migrates to northern area gradually.There is a big difference during the evolution between north and south of the Lufeng Sag:during the early rifting stage,depocenter is located in the south of Lufeng Sag;during the late rifting stage,depocen-ter migrated to north of Lufeng Sag.This study points out that deflection of the stress field direction and differential magmatic diapir activity casued the"seesaw"evolution model in the Lufeng Sag,Pearl River Mouth basin.