Elemental geochemical characteristics of the Lower Cambrian Yurtus Formation in the northwestern margin of the Tarim Basin and their implications for ancient depositional environments and provenance
Facing the contentious and divergent views on the depositional environment of the Yurtus Formation beneath the Cam-brian salt in the Tarim Basin,samples of mudstone and silty mudstone from field outcrops were fully utilized to conduct comprehen-sive analyses of trace elements,major elements,carbon and oxygen isotopes,and rare earth elements. By examining the concentra-tions of signature elements,specific elemental ratios,and integrating structural and sedimentary characteristics,the research delved into aspects such as paleosalinity,paleoredox conditions,paleodepth,paleoclimate,and paleotectonic setting to elucidate the deposi-tional environmental traits of the Lower Cambrian strata. It is found that,in a vertical perspective,compared to the third Member,the first Member is characterized by lower Mg/Al value,higher Sr/Ba value,higher V/Cr value,higher V/(V+Ni) value,higher &U index,lower Sr/Cu value,higher C value,lower Z value,lower Zr/K value and Ti/Al value,higher Baau value and Porg value,and higher paleoproductivity indices Pz and P/Ti ratio,reflecting a paleoenvironment of low salinity,strong reduction,minimal ter-rigenous detrital input,and relatively warm and humid conditions. This led to high total organic carbon (TOC) content within this section,marking it as an effective hydrocarbon source rock interval. Vertically,water depth variations are categorized into four evolutionary stages:deep,sub-shallow,sub-deep,and shallow. Horizontally,the sedimentary water depths exhibit a pattern of Kungekuotan>Xiaorbulak>Sugaitblak,with corresponding sedimentation rates following Sugaitblak>Xiaorbulak>Kungekuotan. In conclusion,the sedimentary environment is identified as a fault-controlled rift deposition within the carbonate platform of the Tarim West. This research enhances the geological theoretical foundation for hydrocarbon exploration beneath the Cambrian salt in the Tarim Basin and offers valuable guidance for both theoretical studies and practical pro-duction in the region.
northwestern Tarim BasinLower CambrianYurtus Formationanalysis of elementdepositional environment
万方数据
维普
