准噶尔盆地吉木萨尔凹陷东部芦草沟组古环境分析OA

To reconstruct paleoenvironment of the Luchaogou Formation in the eastern Jimsar Sag of the Junggar Basin,such as the paleoclimate,paleosalinity and paleo-redox conditions and so on,20 samples from Luchaogou Formation were selected for petrographic analysis and elemental geochemical testing.Multiple discrimination criterias were used-such as Sr/Cu,Rb/Sr,CaO/(MgO·Al2O3),Sr content,Sr/Ba,Mg/Ca,V/(V+Ni),V/Cr,Cu/Zn,Fe/Mn,Rb/K,P/Ti,and P/Al ratios-along with total or-ganic carbon content,to reconstruct the paleoenvironment.The results show that the Luchaogou Forma-tion mainly consists of fine-grained sedimentary rocks,dominated by siltstone and mudstone.These are thick,gray-colored strata primarily composed of mudstone and carbonaceous mudstone,with interbeds of tuffaceous sandstone,argillaceous dolomite,and siltstone containing dolomitic components.During the deposition of the Luchaogou Formation,the paleoclimate tend to be hot and arid.Member Ⅰ was characterized by more intense aridity and heat,there was a gradual transition toward relatively more hu-mid conditions from Member Ⅰ to Member Ⅱ.The depositional environment was saline,with Member Ⅱ showing lower salinity than Member Ⅰ,and Member Ⅰ even exhibiting hypersaline conditions at times.Overall,the redox conditions indicate a dysoxic-anoxic environment.The formation was deposited in a deep-lake setting,with Member Ⅱ representing deeper water than Member Ⅰ.Both members ex-hibit high paleo-productivity,though Member Ⅱ has relatively higher P/Ti values,indicating higher pro-ductivity compared with Member Ⅰ.The study concludes that paleoclimate conditions and paleo-pro-ductivity were the primary controls on organic matter enrichment in Luchaogou Formation,while redox state,salinity,and water depth were secondary factors with relatively limited influence.These findings can provide theoretical guidance for understanding the paleoenvironmental evolution and hydrocarbon generation of the Luchaogou Formation in the eastern Jimsar Sag,Junggar Basin.