Reconstructing salinity and redox variation of permian Lucaogou Formation in the Jimsar Sag, the Junggar Basin, China: Combining trace elements and biomarkers as proxies

The variation in paleosalinity and paleoredox affect the production and preservation of organic matter. The study of ancient salinity and redox conditions of source rocks is of great significance for the enrichment of organic matter and the exploration of petroleum resources. In this paper, the commonly proxies for paleosalinity and paleoredox are distinguished and discussed. The paleosalinity and paleoredox of the Lucaogou Formation in the Jimsar Sag of the Junggar Basin are reconstructed by combining the minerals, corrected elements, biomarkers and isotope indicators. Research suggests that the gammacerane index, carbon and oxygen isotopes, corrected Sr/Ba, and Mg/Al can be used to evaluate the paleosalinity of the Lucaogou Formation. Among the commonly used redox proxies, only V/Cr, U/Th, and VEF can be used to evaluate the redox conditions of the Lucaogou Formation, and their thresholds have been corrected. The paleo-sedimentary environment of the Lucaogou Formation has undergone frequent changes and is generally in a brackish and reductive environment. The paleosedimentary environment is an important influencing factor for the enrichment of organic matter of the study area. A relative higher salinity and reduction environment is conducive to the organic matter enrichment and high-quality source rocks formation in the Lucaogou Formation.