A Study On The Sedimentary Facies Of The Upper Carboniferous-Lower Permian Amushan Formation In Baiyun Obo Area,Inner Mongolia Autonomous Region

The sedimentary facies of the Upper Carboniferous to Lower Permian Amushan Formation in Baiyun Obo area of Inner Mongolia Autonomous region have been systematically studied.The paper has achieved the following main results and understandings:1.Nine types of rocks were identified in the first part of the Amushan Formation.There are6 types of clastic rocks,including fine conglomerate,gravel coarse-grained quartz sandstone,coarse-grained quartz sandstone,medium-grained quartz sandstone,fine-grained quartz sandstone and calcareous mudstone.The types of fossil in carbonate rocks had beed studied,including bivalves,calcareous algaes,echinoderms,calcareous sponges,foraminifera,ostracods,brachiopods,and gastropods.According to Dunham(1962),the carbonate rocks of the first member of the Amushan Formation can be divided into three types: granular limestone,argillaceous limestone,and granular marl.Among them,five types of microfacies had been identified,including angle Conglomerate microfacies,bioclastic conglomerate limestone microfacies,foraminiferous grain limestone microfacies,foraminifera marl marl microfacies and bioclastic marl-bearing microfacies.2.The burial characteristics of Tui had been studied,and the community types of Tui were divided.It is believed that the 13 th and 18 th layers of the Tui in the first part of the Amushan Formation ware buried in situ,and the rest ware buried in different places.The 13 th and 18 th floors ware the residual fossil groups,the 9th floor was the transported fossil groups,and the 11 th,15th and 17 th floors ware all mixed fossil groups.3.The first member of the Amushan Formation can be divided into unbarrier clastic shoreline facies,carbonate platform facies,and tidal flat facies from bottom to top,and the foreshore subfacies and adjacent shore facies in the unbarrier clastic shoreline facies Coastal subfacies,humid internal platform subfacies,open sea platform subfacies and slope subfacies in carbonate platform facies,intertidal and subtidal zones in tidal flat depositional environments,determined the sedimentary model of the first member of the Amushan Formation.