The Comparative Study Of Standard Stratotype-section In Lower Carboniferous At East And West Of Junggar,Xinjiang

The eastern and western Junggar are located in the northern margin of the Junggar Basin.They are an important part of the study of the Central Asian orogenic Belt.The Carboniferous strata in the area are widely exposed and the sedimentary sequence is relatively complete.In this paper,nine Standard Stratotype-section of the Lower Carboniferous strata in the East and West Junggar are used as research objects.According to the “Xinjiang Lithostratigraphy”,the strata are rationally redefined,and we identify the characteristics of stratigraphic rock association,top-bottom contact relationship,marking layer and lithology.Based on the characteristics of Standard stratorype-section,the Carboniferous strata between eastern and western Junggar are comprehensively compared,and this will provide stratigraphy evidence for further understanding of the Carboniferous tectonic evolution process in the East and West Junggar.This paper introduces seven Standard Stratotype-sections in detail.They,from top to bottom,are Heshantou Formation,Aketamu Formation,Nalinkala Formation,Baogutu Formation,Xibeikulasi Formation,Tamugang Formation,Shanlianglishi Formation and Batamayineishan Formation.According to the synthesis research,this paper unravels four aspects of these Formations encompassing its term and evolution,layer profile and introduction,stratigraphic geological characteristics and formation era.Among them,the Aketamu Formation is a newly-built group,which is mainly composed of a series of volcanic rocks and volcaniclastic rocks.The zircon U-Pb age of 332.0±4.7 Ma from rhyolites was obtained,and thus they were formed in the early Carboniferous.A comparative study of the "homonymous strata" in East and West Junggar is considered to have good contrast.By comparing and analyzing Standard Stratotype-section comparison of the Lower Carboniferous in the various layers,the author considers that the stratigraphic sequence of the East and West Junggar in most areas is basically the same.Their sedimentary evolution processes were generally similar,and the whole has good contrast.However,due to the influences of subduction-accretionary of Junggar terrane,the East and West Junggar inherited the structural pattern of the regional Devonian multi-island ocean,which made the sedimentary environment of the local area significantly different.In the Early Carboniferous,the East and West Junggars had fully entered into the marine sedimentary environment;in the Middle and Late Carboniferous,the subduction was further strengthened,the oceanic basin began to shrink,accompanied by volcanic activity,and the sedimentary environment of the East and West Junggar was changed to the sea-land interaction phase.In the early stage of Carboniferous,the eastern and western Junggar areas were developed.With an exception of the Baogutu community,and the rest of the area was progressively developed from the marine-continental interaction to the continental sedimentary strata.