Paleoenvironment and organic matter enrichment in the Kaijiang–Liangping Trough across the Emeishan Large Igneous Province (ELIP)

The Emeishan Large Igneous Province (ELIP) substantially influenced Permian environmental conditions. This study focused on Middle–Late Permian strata in the Kaijiang and Liangping regions, located ∼800 km northeast of the ELIP center, integrating petrology and geochemistry to investigate the influence of the ELIP on the sedimentary environment and organic matter enrichment. Results indicate that the stratigraphic records preserve eruptive products from different developmental stages of the ELIP. The Kaijiang–Liangping Trough underwent initial uplift followed by subsidence from the late Capitanian to the Wuchiapingian, with organic enrichment patterns differing between northern and southern sections owing to tectonic and volcanic activity. In the north, organic matter is enriched in the siliceous mudstones of the Gufeng Member in the late Capitanian and the upper Wujiaping Formation of the Wuchiapingian age, whereas the south additionally contains coastal swamp facies shales at the base of the Wujiaping Formation. Organic matter enrichment was controlled by high productivity and anoxic conditions during the late Capitanian, whereas elevated sedimentation rates and enhanced terrigenous input attributable to volcanic activity became dominant factors in the early Wuchiapingian. Late Wuchiapingian Emeishan felsic volcanic eruptions might have triggered climatic cooling, promoting upwelling restoration and biotic recovery, with anoxic–euxinic conditions and high productivity jointly governing organic matter enrichment. The negative δ¹³C_org excursion during this period might reflect reduced terrestrial organic matter input caused by sea level rise. This study revealed the spatiotemporal coupling of volcanic and sedimentary processes, offering new insights into hydrocarbon source rock formation in large igneous provinces.