Sequence Stratigraphy And Sedimentary System Characteristics Of Fulongquan Fault In Fault Convert Depression Period

Fulongquan Fault locates in the south of Songliao basin,in the junctional zone of the central depression area and the southeast uplift area.The fault depression area is 1000km2 and maximum depth is 5000 m,and it has experienced several tectonic evolution since the cretaceous stage and has fault,depression of dual structure.Denglouku Formation sedimentary period is the transition for fault to depression.In this time,fault activity weaked to disappeared,but it still controlled early syn-sedimentary fault in the early stage.Eastern boundary fault limited deposition scope.Later the basin enter into a period of depression,and syn-sedimentary fault activity gradually disappeared,then sedimentary scope grows.The thickness of east formation is more thick than west formation,and the thickness of north formation is more thick than south formation.The most sedimentary thickness is more than 700 m.In Denglouku Formation of sequence stratigraphy research,we can identify the T4,T3 two secondary sequence interface and a T-3m sequence interface.The Denglouku Formation is divided into two sequence SQ1 and SQ2.SQ1 sequence is identified low-stand system tract,transgressive system tract and high-stand system tract,and SQ2 sequence is identified transgressive system tract and high-stand system tract.Thesis studied the sequence in the plane characteristics and scale and set up the vertical model-Denglouku Formation is from fault to depression,and it's controlled by the boundary fault earlier and beyond it later in plane model,and in sedimentary it is from river delta to fluvial facies sedimentary model of sequence stratigraphy.Because drilling and coring is less and difficult in the study area,the paper recovered the paleogeomorphology of the Denglouku Formation in early stage and found that before Denglouku Formation sedimentary there was two main sedimentary center in north and south and formation is higher in east than formation in west in the early period of Fulongquan Fault.In the SQ1 sequence sedimentary period sand distributed around,and mudstone color is dark gray/ gray in the center of the sub-sag,and on slope it changed to red,purple,so paper inferred that the basin during the period of SQ1 sequence existed in the east,southeast,south,southwest and west five main content source direction.The later SQ2 sequence sand was bangding distribution,and mudstone's color was main red,brown,so paper inferred that east was main content source direction in the period of SQ1 sequence.According 10 coring Wells and 33 well logging and 3d seismic data,in Fulongquan Fault Denglouku Formation thesis identified four types of sedimentary facies,6 kinds of subfacies and 10 kinds of microfacies.Denglouku Formation early main development braided river delta-lacustrine sedimentary system,gentle slope belt in western and eastern actic region is given priority to with braided river delta front deposition,north wing sub-sag,semi deep lake area development and slump deposits,southern Funan sub-sag,shallow lake sedimentary and slump fan deposits.Mid lake basin atrophy,v northern sub-sag area in braided river delta front and shallow lake facies.FuNa sub-sag lakes disappeared,mainly braided river delta front-plain.Late eastern boundary fault control deposition decreased significantly,lake basin area of a sharp contraction,after sedimentary role,it has converted into braided river delta plain braided river sedimentary system.