The Influence of Sedimentary Environment on Organic Matter Accumulation in Wenchang‐B Depression, Zhu‐III Sub‐basin, the Pearl River Mouth Basin, South China Sea

Petroleum and natural gas exploration in the Pearl River Mouth Basin of the South China Sea has been an area of significant interest for researchers. The Wenchang Depression, located within this basin, has developed multiple sets of source rocks. However, the specific mechanisms governing organic matter enrichment remain poorly understood. To elucidate these processes, we conducted Rock‐Eval pyrolysis on 120 mudstone samples from the Paleogene Wenchang (WC) Formation and Enping (EP) Formation, complemented by major and trace element analyses on 140 mudstone samples. Our findings have yielded several key insights: (1) The WC2 unit exhibits significantly higher TOC content and hydrocarbon generation potential compared to other units, establishing it as the most promising source interval; (2) Distinct paleoenvironmental transitions are identified, with EP and WC1 deposited under warm/humid conditions while WC2 and WC3 formed in hot/arid, high‐salinity environments; (3) Most importantly, we demonstrate for the first time that organic accumulation in WC2 is primarily controlled by paleoredox conditions and paleosalinity, whereas WC3 is mainly influenced by paleoclimate and paleosalinity. These findings not only advance our understanding of differential organic matter enrichment mechanisms in rift basins but also provide crucial guidelines for future hydrocarbon exploration in the Pearl River Mouth Basin.