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The Carnian Pluvial Episode (CPE) was a major Late Triassic climatic event, but its recognition in the North China Block remains limited due to challenges in correlating continental strata with global marine records. This study integrates sedimentological, pyrolytic, and elemental geochemical data from the Yanchang Formation in the Ordos Basin to characterize the stratigraphic response to the CPE and evaluate its implications for hydrocarbon exploration. Results show high total organic carbon content and a negative δ13C excursion during the CPE, along with significant shifts in sedimentary microfacies. Palynological assemblages and recent geochronology identify the Chang 73 black shales as products of this event. Enrichments in Fe, P, Cu, and U indicate strong reducing conditions and high paleo-productivity. Elemental ratios (CIA, Sr/Cu, Fe/Mn) reveal a shift from arid to humid conditions between the Chang 8 and Chang 7 units. Redox (V/Cr, V/(V + Ni), U/Th) and productivity (TOC/P, P/PUCC, Cu/Ti) proxies reflect enhanced reducing conditions and elevated productivity, consistent with the CPE. Correlation analyses link lithological transitions and organic matter characteristics to this event, highlighting the CPE as a key control on high-quality source rock development in the Ordos Basin.
Su et al. (Thu,) studied this question.