The Organic And Trace Element Geochemical Characteristics Of The Ediacaran Miaohe Member In The Three Gorges

Selecting Miaohe member of the Miaohe section and Jiuqvnao section in the Three Gorges for research object,Through a comprehensive study of organic geochemistry,elemental geochemistry and isotopic geochemistry to discuss the problems about the maturity of rocks,quality and origin of organic matters,and depositional environments of the ocean.The organic geochemical results show that the organic matter is mainly originated from aquatic organisms such as bacteria and algae in Miaohe member.The relative contribution of bacteria and other prokaryotes is higher than that of eukaryotic algae in Miaohe member.There are differences in relative contribution between algae and bacteria in the vertical The study of hopane,sterane and kerogen show that the organic matter have evolved to over mature stage in Miaohe member.According to the changes of Pr/Ph,gammaceranes value,Trifluorene series of compounds and the results of trace elements show that the Miaohe member is an anoxic,shallow Marine reducing sedimentary environment.It may also have local hydrothermal activity and the effect of intermittent sulfurization.It is found that there are some differences in the sedimentary environment between Miaohe member and Doushantuo ?.It could be two different periods of deposition.During the sedimentary period of Miaohe member,algae growth is more abundant,the sedimentary water body is shallow,and the environment changes little,providing the living space for the living organisms.The environment of relatively poor oxygen and reduction is beneficial to the preservation of organisms as fossils.Therefore,the special ancient Marine environment in Miaohe member has a certain relation with the occurrence of Miaohe biota.and the preservation of fossils.