Study On The Depositional Systems And Lithofacies Palaeogeography Of Triassic-Jurassic In The Area Of Changshou-Fuling,Chongqing

Changshou ~ Fuling area is located in the southeastern margin of Sichuan Basin,and it's stratigraphic regionalization belongs to Yangtze region(?)Yangtze stratigraphic division(?)Wanxian district(?)and Chongqing District(?),the mainland layer is the Mesozoic with development complete,well exposed,the ~ in Triassic marine sedimentary strata,Upper Triassic ~ Jurassic are continental sedimentary strata.In recent years,the regional geological survey of 1:20 and 1:5 has been carried out,and the stratigraphic sequence and regional basic structure frame of the study area have been established.With the East Sichuan gas area of oil and gas exploration and development,oil sector also launched a corresponding investigation of petroleum geology and the corresponding research work,of Feixianguan Formation,Jialingjiang formation,must Xujiahe Formation and Ziliujing formation strata sedimentary environment,sedimentary facies,sequence stratigraphy,sedimentary system and sequence lithofacies paleogeography of the vail et al proposed methods for the deposition sequence of sequence stratigraphy of a certain degree of,made abundant achievements.In this paper,on the basis of previous work,combined with the development of 1:5 000 regional geological survey project,the Triassic Jurassic strata,as the research object,based on the field measured stratigraphic section and route of intensive geological survey as the basis,according to the main characteristics of outcrop,sedimentology,sequence stratigraphy,paleontology,stratigraphy,genesis theory and method,the sequence interface characteristics of long division;Fuling region in three ~ ~ Permian marine sedimentary strata of petrology,sedimentary system,sequence stratigraphy and ~ three Permian Jurassic sedimentary strata lithology,depositional characteristics,genetic stratigraphic sequence characteristics;on this basis,to tectonic sequence system tract as the basic mapping unit,compiled the lithofacies palaeogeography map with accuracy,the advantages of continuity,isochronous causes,discusses the paleogeographic characteristics and evolution of sequence based lithofacies in the region.Through the work,the following progress has been made:(1)On sedimentary characteristics,sedimentary research foundation,sedimentary environment of the study area around the layer are analyzed,study area Triassic Jurassic sedimentary system is divided for 3 types of sedimentary system group and 4 types of sedimentary systems,16 depositional sub facies and a plurality of sedimentary microfacies.Respectively into continental sedimentary system group,including alluvial fan sedimentary system,fluvial sedimentary system,lake depositional system and lacustrine delta sedimentary system;transitional system group mainly delta depositional system.The characteristics of the sedimentary system and the characteristics of the sedimentary facies are also discussed.(2)Sequence interface recognition system domain and stratigraphic stacking patterns and sequence structure conversion sequence features comprehensive analysis as the basis,research in the area of ~ in Triassic marine strata division of the five sequences,the tectonic sequence of the sea flooding surface bounded,each structural layer sequence respectively,is formed by a top,a bottom interface,transgressive systems tract and highstand system tract.In addition to top of a ray of Middle Triassic slope mouth group and Upper Triassic system shall be in the Xujiahe group,between the bottom of bridge group unconformity surface boundary in type ? sequence boundary,and the rest are type ? sequence interface.Due to the special background of deposition in the study area,the shelf margin system domain(SMWT)is generally not developed.On this basis,the characteristics,distribution and developmental control factors of sequence and system tracts are discussed.(3)According to the multiple stratigraphic division principle and genetic stratigraphic theory,combined with the study area of Mesozoic strata characteristics,the work carried out genetic stratigraphic investigation,strata cycle structure and layer,interface recognition of depositional system and stratigraphic stacking patterns of structural transformation and surface growth sequence characteristics,the study area vertical to the filling sequence is divided for 8 stratigraphic units and 3 depositional episodes.The characteristics,distribution and developmental control factors of the various sedimentary scenes are also discussed.(4)To construct sequence system tract as the basic analysis unit,respectively on the ~ in Triassic marine sedimentary strata and Upper Triassic ~ Jurassic sedimentary strata analysis the lithofacies paleogeographic characteristics of the tectonic sequence and tectono depositional episode,describes the different tectonic sequences and system domains of sea Lu Bianqian and lithofacies palaeogeographic evolution.