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The end-Permian mass extinction (EPME) caused a severe decline in marine productivity, leading to a prolonged recovery. Extensive work has been conducted to reconstruct paleoenvironmental conditions during this time, often using numerous geochemical proxies in marine records without assessment of the nature of preservation. Despite Lower Triassic intervals being among the least productive hydrocarbon resources in the Phanerozoic, the Lower Triassic Montney Formation in the Western Canada Sedimentary Basin (WCSB) remains a prolific hydrocarbon system, even with low overall total organic carbon (TOC ≤ 1 wt%). We used this unit to investigate whether geochemical proxies in the Montney Formation preserve primary paleoenvironmental signals, as commonly assumed, or have been overprinted by post-depositional processes such as burial, hydrothermal diagenesis, organic matter thermal maturation, and hydrocarbon migration. We analyzed a 398 m core at ~1 m resolution using δ 13 C org , programmed pyrolysis, bulk elemental geochemistry, organic and scanning electron microscopy (SEM) petrography. The δ 13 C org profile remain consistent with global Lower Triassic carbon isotope records, supporting – but not solely defining – the preservation of a primary signal. In contrast, elemental proxies commonly used for paleoredox and paleoproductivity reconstructions (e.g., Mo, U, V, Ni, Cu, Ba, Zn, P) appear significantly altered by diagenesis, hydrothermal alteration, and hydrocarbon migration. Although these alterations may partly reflect regional environmental variability, petrographic evidence and mineral paragenesis suggest that post-depositional alterations was a major control on elemental distribution. Among the redox proxies - Th/U, shows a good correlation with δ 13 C org and may retain paleoenvironmental significance, despite known complexities in U mobility. Elevated Ti/Na ratios (≥ 0.5) coincide with two negative δ 13 C excursions, and marcasite-replaced sponge spicules, near the Permian-Triassic boundary are consistent with enhanced terrestrial sediment influx and transient ocean acidification and anoxia. These results underscore the importance of integrating petrographic context with isotopic and elemental data to distinguish preserved depositional signals from diagenetic overprints in thermally mature systems.