Responding Characteristics Between Ichnoassemblages And Paleo-water-depth Of The Taiyuan Formation In The Western North China Basin

According to the section studies of the Upper Carboniferous-Lower Permian Taiyuan Formation in Jiaozuo and Yuzhou of Henan Province,Fucheng and Taiyuan Xishan of Shanxi Province,and the research of composition,appearance and distribution characteristics of ichnofossils in the carbonate rocks,combined with the trace elements and major elements,carbon isotopic of burrow fillings and surrounding rocks,try to find out the responding relationships between ichnofossils burrow and the changes of paleo-water-depth,obtained the following progress:?1?According to the analyzation of Sr contents,the values of Sr/Ba,1000×?Sr/Ca?and?¹³C in parts of ichnofossils burrow and the changes of paleo-water-depth,the distribution of ichnofossils is related to the change of paleo-water-depth,especially in the Zoophycos burrows.The Sr contents,the values of Sr/Ba,1000×?Sr/Ca?and carbon isotope of the black fillings are the largest,and the water depth is the deepest.The values of Sr,Sr/Ba,1000×?Sr/Ca?and?¹³C in off-white fillings is the smallest,the water depth is the shallowest,and the values in the red and gray fillings are between them.?2?According to the research of composition,appearance and distribution characteristics of ichnofossils in the carbonate rocks,combined the results of geochemical data,types of ichnoassemblages with different water-depth were established:One,Nereites-Chondrites ichnoassemblage,occurred in the lower zone of shallow sea below the redox interface;Second,Zoophycos-Teichichnus ichnoassemblage,formed in the middle zone of the shallow sea between the wave base and redox interface;Third,Zoophycos-Thalassinoides ichnoassemblage,occurred in the upper zone of shallow seas?between the sea level and wave base?or lagoon sedimentary environments.?3?According to the comprehensive analysis of the ichnoassemblages and geochemistry of study area,the responding relationships between the ichnoassemblages and the paleo-water-depth changes is proposed:as the depth of the seawater gradually deepens,the ichnoassemblages is from Zoophycos-Thalassinoides to Zoophycos-Teichichnus to Nereites-Chondrites.In conclusion,based on the changes of above-mentioned ichnoassemblages in the Taiyuan Formation,the evolution law of transgression and regression within the depositional stage of the Taiyuan Formation in different areas were suggested.