Characteristic Of The Tectonic And Paleogeomorphic Evoluation In Fulongquan Fault Depression,Songliao Basin

Fulongquan fault depression is located in the south of Songliao basin,and in the boundary belt of southeast uplift area adjacent to the central depression area.The fault depression area is about 1000 km~2 with a maximum depth of about 5000 m.It has experienced several tectonic evolution since the cretaceous stage with a typical double-layer geologic structure of rift-depression.The author has used the data of drilling,logging and core and plenty of 2d and 3d seismic data in this paper.Basing on the integrated use of the basic theory of sequence stratigraphy,structural geology,sedimentary petrology,basin analysis,and predecessors' research results,we used an analysis method of comprehensively analyzing with the combination of geological analysis and geophysical interpretation to research the characteristics of Fulongquan downfaulted basin tectonic-ancient landform evolution.Based on the fine structural interpretation of the stages and classification in Fulongquanfault depression,the tectonic stages and the characteristics of the boundary faults are analyzed systematically.The basin structure style are determined by the characteristics of the boundary fault,and it is considered that the rift ofFulongquan can be classified into three sub-depresssion.Depending on the type of gentle slope belt Fulongquan fault depression is classified into three kinds of fault basin structural style,Gujiadiansub-depresssion has a flexural gentle slope type fault basin structural style,Funansub-depresssionhas a smooth synthetic fault terrace type fault basin structural style,And Fubei sub-depresssion has a narrow steep slope fault terrace type fault basin structural style;Through the synsedimentary fault studies,this paper subdivided the tectonic activity and stage characteristics of the downfaulted basin,concludeing that the fault depression has a "weak-strong-weak " tectonic activities stage characteristic and that the characteristic of the intensity of fault activity is strong in south while weak in north at the early stage,at the middle-late the situation is just on the contrary.Through 3d seismic data analysis we gained the qualitative identification of ancient landscape pattern,through the analysis of the tectonic evolution of we indire-ctly researched the development of the ancient landform evolution,and through erosion thickness restoration such as compaction correction method we could get quanti-tateive restore original formation sedimentary characteristiccs.In this paper,the authors synthesize the study methods above to analyze the tectonic-paleogeomorphology evolutionary characteristics of the rift depression of the Fulongquan.The study suggests that the tectonic-paleogeomorphology framework of the subsidence of Fulongquan is "west-east dissimilitude and north-south differentiation".And corresponding to different tectonic evolution stages paleogeomorphology units' combination also varies,during rift period the tectonic-paleogeomorphology general characteristic is deep in south while shallow in northat the early stage,at the late stage the situation is reverse.Based on the analysis process and conclusion above,this paper also discussed the three main factors of the tectonic evolution of the region which control the paleogeomorphology characteristic.The factors are the basin structure styles,the major faults and erosion unconformity.