The Formation And Evolution Of Northern Liaodong Dome

The northern Liaodong dome is located in the Liaodong bay depression in the northeast of the Bohai sea.Tan-Lu fault is the main controlling tectonic factor in the Liaodong bay depression.Affected by the strength,the character and transformation of activity mode of Tan-Lu fault in Cenozoic,the structural development characteristics and hydrocarbon accumulation conditions in study area are complex.Combined with seismic,drilling,logging and other data,this paper systematically analyzes the structure and transformation process of the northern Liaodong dome.Combined with the regional geological setting,the dynamic mechanism of Liaodong dome is analyzed by means of analogue modelling and numerical simulation of stress field.Based on seismic and drilling data,the structural characteristics of the Cenozoic northern Liaodong dome are revealed.The results show that Liaodong dome is controlled by Liaozhong No.2 fault and Liaodong fault.In Ek-Es3 sequence,Liaozhong sag is deposited,and Liaodong dome is not deposited as part of Jiaoliao terrane.In Es2-Es1 sequence,The main sedimentary center of study area is located in Liaozhong sag,and the secondary sedimentary center is located in the southern Liaodong sag.The northern part of Liaodong dome separates rock formation obviously,and the southern part is still a part of Jiaoliao terrane.In Ed sequence,Liaodong dome divides Liaozhong sag and Liaodong sag,and there are two main NNE-trending sedimentary centers.The Liaodong dome is separated from the Jiaoliao terrane,and begin to be deposited as an underwater dome.In the top of Ed sequence,the formation is denuded.In N-Q sequence,controlled by the regional subsidence,Liaodong dome is covered as a whole one.Based on the analysis of fault activity rate,balanced profiles and apatite fission track,the Cenozoic tectonic evolution of northern Liaodong dome is defined.At the Ek-Es3 depositional stage,Liaozhong No.2 fault divided Liaozhong sag and Jiaoliao terrane,and the eastern part of Liaozhong No.2 fault didn't form.Therefore,as part of Jiaoliao terrane,Liaodong dome continued to uplift.At the Es2-Ed depositional stage,the activity of Liaodong fault began to strengthen and the number of secondary faults increased.The activities of Liaozhong No.1 and Liaozhong No.2 faults continued.The Liaodong dome gradually separated from the Jiaoliao terrane and evolved as a separate dome.At the N-Q depositional stage,the Liaodong dome began to disappear and the strata were deposited extensively.The Liaodong dome entered into the subsidence stage along with the peripheral sag.Combined with regional geological background,the structural transformation mechanism of northern Liaodong dome is revealed by analogue modelling and numerical simulation of stress field.At the Ek-Es4 depositional stage,the regional tension stress and dextral shear stress were weak,resulted in the initial formation of Liaozhong sag.Liaodong dome moved together as part of Jiaoliao terrane in this period.The regional tension stress began to increase during the Es3 depositional stage,and the study area inherited the previous tectonic framework.At the Es2-Ed depositional stage,the regional shear stress began to increase,and the tension stress weakened.The dextral strike-slip stress of Tan-Lu fault was strengthened,which was characterized by dextral transtensional stress,and the Liaodong dome separated from Jiaoliao terrane and began to develop.At the end of the Ed depositional stage,the stress properties of the basin changed from regional tension to regional compression,and the strike-slip effect was strengthened.The Tan-Lu fault changed from dextral transtensional movement to dextral compresso-shear movement,and the dome and its surrounding strata were denuded.At the N-Q depositional stage,the regional shear stress was strong and the tensile stress was weak.The study area entered into the depression stage.