Provenance Analysis And Sedimentary Characteristics Of Yanghugou Formation In The Western Margin Of The Ordos Basin

In recent years,with the development of oil and gas exploration in the Ordos Basin,it is found that the carboniferous Yanhugou Formation in the western margin of the basin has a certain exploration potential,but the provenance and sedimentary characteristics are not well understood.This dissertation takes the carboniferous Yanghugou Formation in the western margin of Ordos Basin as the research object,takes sedimentology,petroleum geology and other disciplines as the theoretical guidance,and combines the regional geological data,field geological profile,drilling core,geochemical test data of others scholars.In this dissertation,the stratigraphic development,provenance and sedimentary characteristics of Yanghugou Formation are systematically studied.The achievements include:Through observation of field geological profile and analysis of logging data,it is concluded that the Yanghugou Formation and Ordovician or older strata in the study area have unconformable contact,or they have conformable contact with the underlying Jingyuan Formation.It was deposited continuously with the overlying Taiyuan Formation.The formation thickness of the Yanghugou Formation is thick in the west and thin in the east.The central Wuzhong area is the sedimentation center of Yanghugou period due to its rapid sedimentation rate and large thickness of the formation.The provenance is mainly from the upper crust felsic rocks in the continent.The northern provenance area is a recycling orogeny area.And the parent rock is mainly shallow metamorphic rocks from the Alxa ancient land and a small amount of volcanic rocks.The southern provenance area is mainly a recycling orogeny area and stable continental blocks.And the parent rock is mainly the shallow metamorphic rocks in the Qilian-North Qinling orogenic belt,followed by carbonate rocks and volcanic rocks.The tectonic background of the provenance area is dominated by the passive continental margin,but there are differences between the north and south provenance areas.Using field geological profiles,drilling cores and other data,through analysis of sedimentary signs,logging facies signs,paleontological signs,and geochemical signs,it is concluded that the Yanghugou Formation tends to be mild and humid,brackish water,weak oxidation-reduction sedimentary environment.And it can divided into three types of sedimentary systems: continental shelf facies,barrier coast facies,and tidal delta,which can be subdivided into tidal control delta front,barrier island,tidal flat,lagoon,tidal delta,terrestrial debris continental shed,mixed seven sedimentary subfacies.At the same time,based on the analysis of provenance,the plane distribution of the Yanghugou Formation was studied to establish its deposition model.