Lithofacies Paleogeographic Distribution And Evolution Of The Late Devonian Donghe Sandstone Segment In The Northern Tarim Basin

Based on the theory of ancient geography and clastic rock sedimentology,the comprehensive application of core,thin section,conventional logging data,the stratigraphic characteristics,the petrologic feature,the sedimentary facies types and the longitudinal and transvers distribution of the Late Devonian Donghe sandstone formation of the north of the Tarim Basin were studied;combined with the regional geological background,"the single factor analysis and multifactor comprehensive mapping method" adopted,the Donghe sandstone formation thickness,the sand thickness,sand ratio as three single factor serve as the key control factors,established the Late Devonian Donghe sandstone formation of the north of the Tarim Basin lithofacies palaeogeography map,analysised the paleogeographic evolution and distribution in different periods of the Donghe sandstone formation.The Donghe sandstone formation in the area differ greatly in thickness,most between 0-300m,suffered structural greatly changes during the deposition reaction.The Donghe sandstone sedimentary in the area mainly is clastic rocks,the Donghe sandstone section of Halahatang area,Donghetang area,Hudson region is mainly fine sandstone sediments;Lungudong area,grass lake area,Lunnan area consists of conglomerate,pebbly sandstone,sandstone,fine sandstone,siltsione and argillaceous siltstone,calcareous siltstone and mudstone rock sediments.The sedimentary facies types in Donghe sandstone formation manily include wave controlled shore facies,tidal flat facies,alluvial fan facies,subfacies mainly include equal,shoreface,foreshore,shore,coastal dunes,supratidal,intertidal,subtidal,fan,fan subfacies.From west to East,the sedimentary facies of Donghe sandstone formation varys from littoral environment of no barrier and wave control in both ends to the Lunnan area,which is located in the middle of the area and not deposited the Donghe sandstone sedimentary.From north to south,the sedimentary facies of Donghe sandstone formation varys from the area which is not receiving deposits in Lunnan to foreshore sediment.Other sedimentary facies' distribution is relatively small.Through the thickness of strata contour map,sand body thickness contour map' sand ratio contour map 3 single factors,the lithofacies palaeogeography is established in study area:Halahatang area and Donghetang area,which is far from the pinch out line,is the foreshore-nearshore depositional environment;Hudson region,which is close to the pinch out line,is the foreshore depositional environment.