Variation Characteristics Of The Ichnofossils And Paleoenvironment In The Upper Carboniferous-Lower Permian Taiyuan Formation Within The West Region Of North China

The Upper Carboniferous-Lower Permian Taiyuan Formation in the west region of north china is an set of marine and interbedded with fusulinid,coral and other marine body fossils as well as Zoophycos,Teichichnus,Nereites,Chondrites,Rhizocorallium and other ichnofossils,which contains rich resources such as coal,coalbed methane and shale gas,and develops.Based on the section studies of the Upper Carboniferous-Lower Permian Taiyuan Formation in Fucheng area of Shanxi province,Jiaozuo and Yuzhou area of Henan province,this paper analysis the carbon and oxygen isotopes and microelements with different color fillings of Zoophycos burrows,and try to find out the changes of ancient sea level in deposit time of the Taiyuan Formation and the trace fossil responding characteristics to the paleo-oxygenation phase,obtained the following progress:?1?Distribution and compostion characteristics of ichnofossils in different limestone beds of this fomation.?2?Based on analysis of carbon and oxygen isotopes in the different color fillings of Zoophycos burrows,it is found that the?¹³C value from black fillings is higher than that of rufous,the?¹³C value of rufous fillings is higher than gray,the?¹³C value of gray is higher than offwhite,therefore it is speculated that the sea level from low to high with offwhite to gray to rufous to black in the fillings of Zoophycos burrows.?3?After analyzing microelements?mainly V?Ni?Ce?La?in different color fillings of Zoophycos ichnofossils,found that the V/V+Ni value is between 0.3-0.36 in the offwhite and grey fillings and the Ce/La value is between 0.6-0.9;the V/V+Ni value is between 0.5-0.55 in the rufous filling;the V/V+Ni value is between 2.8-3.5 in the black fillings,so it can be speculated that the Zoophycos with offwhite and gray fillings reflects aerobic,oxidizing environment;Zoophycos with rufous fillings indicates dysoxic,weak reduction environment;and with Zoophycos black fillings found in anaerobic conditions,reducing environment.The oxygen content reduced with the color of fillings changing from offwhite to gray to rufous to black.?4?The three regions experienced two major transgressions,the first transgressive horizon is L₁ limestone layer in the Fucheng area,L₄ limestone layer in Jiaozuo area,and L₂ limestone layer in the Yuzhou area;The second time is the L₇ limestone layer in the Fucheng area,L₈limestone layer in the Jiaozuo area,and L₆ limestone layer in the Yuzhou area;in which the largest transgression occurred the black fillings of the Zoophycos burrow in anaerobic environment.?5?Analying the composition and test data of the trace fossils of the Taiyuan Formation,propose the corresponding relationship pattern of three kinds of ichnofossils with aerobic,dysoxic and anaerobic phase.The ichnofossils deposition environment with aerobic phase formed in carbonate platform in the upper shallow marine environment;the ichnofossils deposition environment with dysoxic phase occurred in the lower part of the shallow marine environment or limited bay and lagoon environment;the tichnofossils deposition environment with anaerobic generated in the carbonate platform in the lower part of the shallow marine environment.