| The Fulongquan faulted depression is located in the southeastern part of the Songliao Basin,which is a half-graben with "faulting in east and overlapping in west".The phases of the boundary fault activity intensity change control the formation,development and evolution of the basin.At present,oil and gas has been found in the Yingcheng formation,indicating a good prospect of oil and gas exploration.Therefore,this paper takes the Yingcheng formation of Fulongquan faulted depression as the research object,the basic theory and method of tectonic geology,sequence stratigraphy and sedimentology are applied,and the data such as seismic,drilling /logging,core and test analysis are used to carry out study of the tectonic-sequence stratigraphy.Based on the analysis of the tectonic activity,basin structure and paleo-structural geomorphologic features of Yingcheng formation in Fulongquan fault depression,the sequence stratigraphic framework of the whole basin was established,and the development and evolution characteristics of sedimentary facies and sedimentary system were determined clearly.Then the sequence stratigraphic structure of the Yingcheng formation in the Fulongquan faulted depression was summarized.In addition,the relationship between sequence-sediments and tectonic was discussed,which provides the geological basis for oil and gas exploration in the Fulongquan fault depression,and also provides an example for the study of tectonic sedimentary studies in similar rift basins.The three main boundary faults of the Fulongquan faulted depression control the formation,development and sedimentary filling process of the three sub-depressions of Fubei,Funan and Gujiadian,and the activity of the boundary faults in the Yingcheng formation is characteristic of "the northern boundary fault was more activity than the southern part,and these faults are more activity in the early stage".Based on the restoration of the early paleo-geomorphology of the Yingcheng formation,the structure is appeared with the pattern of "west-east direction,the north deep and south shallow",and further divided into seven different geomorphic units.According to the seismic and drilling sequence interface identification,two third-order sequences(SQ1 and SQ2)were identified in Yingcheng formation ofFulongquan faulted depression.Each sequence was further divided into LST,TST,HST.Combined with the analysis of core observation,thin slice identification,drilling/ logging and seismic data,the main sedimentary facies such as fan delta,braided river delta,underwater fan and lake are recognised in Yingcheng formation of Fulongquan faulted depression.From the early stage to the late stage of the Yingcheng formation,the stratigraphic distribution area gradually expanded,the difference of geomorphic decreased,the sediment grain size was thinner,the depositional center and subsidence centers migrated from south to north.the sedimentary system is transformed from the early fan delta,underwater fan-lake sediments to late fan delta,braided river delta-lake sediments.The difference of the tectonic pattern is obvious in different regions from the north to the south in the study area,according to the three different basin structural morphologies,internal structure of the sequence and the characteristics of sedimentary depositing and filling,three typical sequence structures are identified in Yingcheng Formation of Fulongquan faulted depression,multi-level fault-terrace type,gentle slope type and flexure slope break type.Comprehensive analysis shows that the spatial-temporal differences of the three main boundary faults on the east side of the Fulongquan faulted depression have important control effects on the formation of the sequence boundary,the variation of the accommodation space and the internal structure of the sequence stratigraphy.The different tectonics palaeo-geomorphic units have obvious control action on sedimentary facies type,sandbody distribution and sediment filling method. |
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