The Study Of Ancient Geography In Guizhou Dejiang Area Silurian Sequence Lithofacies

In recent years,China's shale gas exploration has made some important breakthroughs and discovery in Guizhou,Sichuan and so on.Guizhou Dejiang area as shale gas in South China one of the best areas of formation and development,so the area Dejiang Silurian stratum system,palaeontology feature,sedimentary system,sequence stratigraphy,palaeogeography and evolution of sequence based lithofacies and regional tectonic background,provide the basis for the practical exploration work,has made understanding the following points:1)Based on detailed field investigation combined with the stratigraphy of the new rock strata and regional geology,Silurian strata of the studied area to study science,the strata of Cambrian,Ordovician,Silurian,Permian,Triassic and Quaternary strata in a region,mainly from the Cambrian Paleozoic strata,the development of the for a wide range,including Silurian Longmaxi group(O3S1l group),the new beach(S1xt),Songkan group(S1s),shiniulan group(S1sh),group(S1m),away Chong Rong Xi group(S1r),Xiushan group(S1x).2)Based on the detailed stratigraphic study on the sedimentary environment of the study area were analyzed,the Silurian is Dejiang is divided into 3 sedimentary environment system,respectively.(1)The continental shelf sedimentary system.(2)Carbonate platform depositional system.(3)Shore shallow sea sedimentary system,the characteristics of the corresponding sedimentary system are further studied.3)Based on field investigation and data collection,the sequence stratigraphy of Silurian in the study area is divided into 1 system tracts SS4 and 7 three order sequences(SSQ1-SSQ7),SSQ1-longmaxiformation?SSQ2-new beach formation?SSQ3-Songkan group?SSQ4-shiniulan group?SSQ5-group rushed away ?SSQ6-dissolved stream group?SSQ7-Xiushan formation;The bottom interface of the sequence is of type II interface.On this basis,combined with regional tectonic background,each sequence is composed of transgressive system tract(TST)and highstand system tract(HST).4)Based on the study of the sequence and depositional system of the Silurian system in Dejiang area,this paper,based on the study of the three-stage sequence system as the lithofacies palaeogeographic mapping unit,The SSQ1-Longma River Formation is mainly composed of muddy deep shed system,and the SSQ2-Xintan Formation is mainly composed of muddy deep shed system and silty shallow continental shelf system.SSQ3-Songkan Formation For the gray land shelf system,gray matter-mud mixed plot shed,SSQ4-stone cattle bar group mainly for the open platform system and the point of the beach system,SSQ5-horse foot red group for the silty shallow shelf system,SSQ6-Mainly for the shredded shrub,SSQ7-Xiushan group for the shale shallow shelf system and silty submarine system.