A Biomarker Study On The Late Permian Coals From Eastern Yunnan-western Guizhou Region

The eastern Yunnan–western Guizhou region is the most important coal production base in southern China,and the coal seams in the study area represent the plant groups that formed the late Permian coal in China.This paper tries to find the information of the last Permian land plants group through the study of biomarkers.In this paper,the late Permian coal in eastern Yunnan–western Guizhou was taken as the research object,and compared with the early Permian coal in Ningxia and Xuzhou in North China,so as to analyze the important information such as organic matter composition,biomarker characteristics of coal–forming plants and molecular markers of sedimentary environment.The results of organic geochemical analysis show that almost all the coals in the study area have evolved to a mature stage.The analysis of pyrolysis hydrogen index HI and organic carbon isotope composition shows that the organic matter types of the coals in the study area are mainly typeⅢ₁and typeⅢ₂,and humic organic matter is dominant.However,the organic matter types of some coals in Xingyun Coal Mine of Fuyuan and Dahebian Coal Mine of Shuicheng are typeⅠand typeⅡ.Therefore,the bio-organic geochemical action of bacteria and algae in the accumulation and evolution of organic matter in coal measures and the biomass of bacteria and algae also have certain influence on the organic matter of coal.Molecular organic geochemistry shows that the organic matter in coal mines in the study area is mostly the dual source of lower aquatic organisms and higher terrestrial plants.According to the Pr/Ph ratio,it is judged that the coal–forming environment of Naluo Coal Mine of Shuicheng belongs to weak oxidation environment,while the coal–forming environment of other coal mines belongs to typical oxidation coal–forming environment.Three fluorene content analysis found that the coal in Dahebian Coal Mine,Wangjiazhai Coal Mine and Naluo Coal Mine of Shuicheng had high content of sulfur fluorene,which was greatly affected by seawater intrusion,which was consistent with the average distribution of total sulfur in coal.The regular steranes of late Permian coal in eastern Yunnan-western Guizhou all show the advantages of C₂₉steranes over C₂₇ steranes.Considering the dual sources of C₂₉ steranes,that is,from higher plants and algae,combined with the geological environment evolution of the study area,it is speculated that the coal in the study area is mainly derived from terrestrial higher plants,and with the change of sea level,lower students also have a certain amount of input.The content of C₂₈ sterane in coal of Xuanyantang Coal Mine is high,and it is speculated that the higher C₂₈ sterane is related to the development of fungi.Through the study of diterpenes,it is found that the abundance of tricyclic diterpenes and tetracyclic diterpenes in Dahebian Coal Mine of Shuicheng and Xingyun Coal Mine of Fuyuan is relatively high,while that in Yantang Coal Mine of Xuanwei,Tianba Coal Mine of Xuanwei,Wangjiazhai Coal Mine of Shuicheng and Naluo Coal Mine of Shuicheng is relatively low.Therefore,the content of markers contributed by gymnosperms and coniferous gymnosperms in Dahebian Coal Mine of Shucheng and Xingyun Coal Mine of Fuyuan is significantly higher than that in other coal mines.Compared with coal from Ningxia and Xuzhou in North China,the contribution of gymnosperms in coal–forming plants increased gradually from South China to North China,and the contribution of coniferous gymnosperms also increased gradually from South China to North China.