Research Of Organic Reef And Depositional Environment Of The Carbonaceous Of Northeasten Qaidam Basin

Based on the previous research results,this paper combines the regional macroscopic characteristics with local microcosmic anatomy to study the developmental characteristics and sedimentary evolution of the reefs in the study region,based on the Carboniferous reefs in the eastern of Qaidam Basin.The characteristics,distributional horizon and law(and its evolution)of the Carboniferous reefs in the eastern margin of Qaidam Basin were studied by field outcrop excavation,drilling core observation,laboratory sedimentary petrology research and bioassay.The reefs in the eastern margin of the Qaidam Basin are mainly distributed in the lime ditch,the wall gouges,and the Gahai Nanshan section around the Oulong Brook area.The reefs are mainly point distributed in the strata,and they are distributed in a discontinuous band.The size of the monolith is relatively small,and the regional development is relatively extensive.Based on the anatomy of typical reef reefs,the biology and rock composition of the reefforming strata are clarified.The results show that the reefs are mainly coral and sea lily and the reefs include brachiopods,gastropods,bryozoans,foraminifera etc.the reef rocks are mainly composed of the coral skeleton limestone,coral granular limestone,barrier rock,cohesive rock,clastic limestone and the biological clastic limestone.Based on the analysis of the sedimentary facies and sedimentary environment in the study area,the sedimentary facies of the eastern margin of the Qaidam Basin are mainly divided into alluvial fan facies,fan delta facies,platform facies,organic reef facies,tidal flat facies –lagoonal facies-barrier island facies etc.The organic reef facies are mainly divided into reef basins,reef cores,reef covers.In addition,according to the relevant tests,fossil identification and other methods,the analysis of the growth,development and evolution law of reefs in the eastern Qaidam Basin,consider that the reef evolution is divided into four stages: incubation period,biological extinction events in late Devonian to the early Carboniferous wall ditch group sedimentary period;the recovery period,the paclitus group deposition period;the prosperous period,Mid-term;the depression period,The paclitus group sedimentary period to the Crocker group sedimentary period.Based on the study of sedimentary facies,sedimentary microfacies distribution and tectonic sedimentary evolution,the results show that the reefs in the Eastern margin of Qaidam Basin are mainly prosperous in the middle and late Carboniferous.According the characteristics of the sedimentary environment change in the Late Carboniferous and the reef,this paper summarizes the reef-forming model of Carboniferous reefs in the eastern margin of Qaidam Basin,which is mainly patch reef model in the carbonate platform and bank.