Biomarker Characteristics And Sedimentary Environment Analysis Of Cambrian Thrombolite Microbolites In Western Shandong Province

There are a large number of Microbial Carbonates in the Cambrian of Western Shandong Province,which are rich in types,diverse in characteristics,well exposed and dolomitized in varying degrees.At present,the study of Cambrian microbial rocks in western Shandong is only focused on the trace of microbial activities,but few on the complex microbial types that affect their diagenesis.In this paper,through field observation,microscopic observation and the use of organic geochemical means,the biomarker compounds of microbial rocks are analyzed from the molecular fossil level,the microbial limestone and dolomitization microbial limestone are compared,and then the agglomerate is taken as an example to explore the types of microorganisms and the microbial activities that affect the diagenesis of Cambrian microbial rocks in western Shandong Province.By GC-MS and XRD,the mineral composition and molecular biomarker identification of conglomerates and dolomitized conglomerates in Zhangxia formation and Chaomidian formation of Cambrian in western Shandong Province were carried out.The results showed that the main compounds were sterane,tricyclic terpane and cablin,of which the proportion of hopane biomarkers was More than 70%,indicating that the source of the agglomerate in the process of diagenesis is mostly prokaryote.Under the microscope,a large number of cyanobacteria calcification traces are in strong contrast with trace biomarkers,and there may be a large number of degradation of cyanobacteria in the diagenesis.However,tricyclic terpane(<C30)is suspected to be isoprene derived from the precursor of methanogenic archaea.In addition,the high ratio of ??/???10 reflects the existence of anaerobic methane oxidation.The change of l-hopane may also be related to sulfate reducing bacteria.Combined with the analysis of the X-ray diffraction data of the microbial rocks,it is found that in the rocks with more dolomite or more Mg2+ minerals such as low Mg calcite,the biostandard concentration also increases significantly.The trace of microorganism found in microbial rocks is of great theoretical significance to explain the influence of microorganism activity on Dolomite Precipitation Process in the genetic model of microbial dolomite.