Lithofacies And Paleogeography Analysis On The Northwestern Margin Of The Junggar Basin

The Jiamuhe Formation in the northwestern margin of the Junggar Basin is composed of volcanic rocks,pyroclastic rocks and sedimentary rocks.It is characterized by large thickness and wide distribution and is favorable for oil and gas accumulation,thus has great prospects for exploration and development.Lithofacies paleogeography research plays a vital role in petroleum geology research and the exploration and development of oil and gas reservoirs.At present,the researches on lithofacies and paleogeography of the Junggar Basin have mostly focused on the entire Permian,and little attempts have been conducted on short time scale.At the same time,previous studies have mostly concentrate on the entire Junggar Basin and little detailed work has been attempted to assess the lithofacies and paleogeography of a smaller typical area.And the detailed study seems to be necessary for further oil and gas exploration and development.Logging data,core and thin section data in the study area,according to the volcanic zircon U-Pb dating method,reveals that the Jiamuhe Formation is a late Carboniferous-Early Permian inter-age strata,which is divided into three sections,from bottom to bottom.The upper part is Jia1(310Ma?319Ma),Jia 2(310Ma?290Ma),and Jia 3(290Ma?278Ma).The Jiamuhe Formation identified TC2j1,TC2j2,TP1j3,and the top interface(TP2w and TP1f)of the Jiamuhe Formation.TC2j1 is a regional unconformity surface,and the Jiamuhe Formation top boundary TP2 w unconformity surface was found in the Zhongguai area.The strata of the Jiamuhe Formation in the study area are composed of eruptive facies volcanic clastic rocks and pyroclastic sedimentary rocks,overflow facies volcanic lavas,volcanic sedimentary facies pyroclastic lavas and sedimentary pyroclastic rocks,and sedimentary lithofacies clastic rocks.Class composition.Volcanic eruptive facies and overflow facies volcanic-pyroclastic rocks are mainly developed in the Zhongguai Uplift,Kebai Fault Zone and Wuxia Fault Zone,and sedimentary facies are mainly developed in Mahu Sag,Badasong Uplift and Pen 1 Well Sag.Mudstone,sandstone.During the deposition of the Jiamuhe Formation,the study area was in the final period of ocean-continent transition.There are a large number of Yangdao volcanic rocks and tholeica alkaline volcanic rocks with crust mixed dyeing characteristics in the area,indicating that the area is in the post extension collision environment.This paper uses the single-factor analysis-multi-factor comprehensive mapping method to study the lithofacies paleogeography of the Jiamuhe Formation in the northwestern margin of the Gar Basin to determine the lateral and vertical evolution characteristics of lithofacies.