The Comparative Study On The Upper Devonian-lower Carboniferous Standard Stratotype-section Profiles In The Eastern And Western Junggar,Xinjiang,NW China

In this paper,the Upper Devonian-Lower Carboniferous diachronic strata in eastern and western Junggar of Xinjiang are taken as the research objects.According to the basic requirements of the“STRATIGRAPHIC GUIDE OF CHINA”for the establishment,comparision,stratigraphic redifinition and determination of lithostratigraphic units,these strata in Junggar area are redifinated and revised.It is mainly focused on the characteristics of rock assemblages,top-bottom contact relationships,geochronology,lithofacies,regional distribution and thickness change.Based on rock assemblages,bio-fossil assemblages,contact relationships and sedimentary environments for these units,we conclude the following results.It is confirmed that three diachronic lithostratigraphic units from Late Devonian to Early Carboniferous in eastern and western Junggar occur encompassing Taerbahatai Formation?D₃C₁t?and Hongguleleng Formation?D₃C₁h?in western Junggar,and Jiangzierkuduke Formation?D₃C₁j?in eastern Junggar.There is sufficient evidence on the top-bottom contact relationship and paleontological fossil assemblage.Moreover,in the eastern and western Junggar areas,there are no similarities among the three formations during this period.This paper revises the starting and ending coordinates of the stratotype profile of the Taerbahatai Formation.The starting coordinates are?86°44?14.9?E,47°05?14.7?N?and the ending coordinates are?86°42?41.8?E,47°05?29.6?N?.By comparing the diachronic lithostratigraphic units from Late Devonian to Early Carboniferous,it is found that the three sedimentary facies are dominated by submarine facies.They have some similarities on biofossil assemblages and top-bottom contact relationships,but the three formations have their own particularities especially on the difference of their rock assemblages.As a whole,it is not comparable,and therefore supports the independent establishment of Formation-Level strata in different zones with ages ranging from Late Devonian to Early Carboniferous.From Late Devonian to Early Carboniferous,East and West Junggar underwent frequent reciprocal regression-transgression processes.Although the submarine facies environment was dominant in general,the western Junggar was a stable and continuous deposit?shown as regional integration contacts?,and the subsequent transgression process was dominant,cause the sea area has been further expanded.While the eastern Junggar suffered plate subduction and grological body terrane,as a result,relatively intense volcanic activity erupted?shown as dominant volcanic rocks in Jiangzierkuduke Formation from Late Devonian to Early Carboniferous and interlayer of volcanic rock in Jiangbasitao Formation of Early Carboniferous in East Junggar?.It is accompanied by tectonic movement in the whole region?shown as regional unconformities and faults?.The movement resulted in rapid uplift in some areas and rapid transformation of sedimentary facies into continental or marine-continental interfacies.