Sedimentary Types And Their Sedimentary Environments Of The Carboniferous-permian Taiyuan Formation In Northeastern Qinshui Basin,Shanxi Province

The Upper Carboniferous-Lower Permian Taiyuan Formation in northeastern Qinshui Basin of Shanxi Province contains abundant coal and coalbed methane resources,and well outcrops in the area of Heituyan village in Xiyang County.Based on the researches of the outcrop section and some nearby exploration data,this paper detailedly analyzes the lithologic characteristics,sedimentary structures,fossil composition,carbonatite microfacies and sedimentary sequence types of the formation and obtains the results as follows: First,according to observing limestone specimens by using polarized microscope in the 5 beds of limestones in the Taiyuan Formation,this paper identified many kinds of biodclasts,including foraminifers(fusulinids and foraminifers except fusulinids),brachiopods,bryozoans,echinoderms,ostracodes trilobites debris and recognized four kinds of limestone microfacies such as bioclastic micrite microfacie,fine powder crystal limestone microfacie contained bioclasts,coarse powder crystal limestone microfacie contained bioclasts,fine powder crystal bioclastic limestone microfacie.Second,this paper recognized three kinds of sedimentary systems,including barrier shore,open shore and delta,and five kinds of sedimentary facies as barrier island,lagoon,tidal flat,shallow sea,delta facies,and three kinds of sedimentary subfacies such as mixed flat,mud flat or peat flat,delta plain subfacies,and five kinds of microfacies as distributary channel,natural levee,crevasse splay,flood plain and peat swamp.And this paper identified the mixed tidal flat deposits in the middle part of the Taiyuan formation.Third,this paper put forward distributional model of paleoenvironment of nine kinds of sedimentary sequence types and sedimentary environment model on the basis of vertical variation of sedimentary sequence in the Taiyuan Formation.And this paper briefly discussed the vertical evolution process of depositional environments,i.e.,from the bottom to top,ranging from barrier island-lagoon-tidal flat to shallow sea-tidal flat,and then to delta environments.