Chemostratigraphy across the Permian-Triassic Boundary: The Effect of Sampling Strategies on Carbonate-carbon Isotope Stratigraphic Markers

A major extinction pulse occurred just below the conodont‐defined Permian‐Triassic boundary. Global‐scale compilations of increasingly larger paleontological, sedimentological, and geochemical datasets further amplify our understanding of this event by unraveling temporospatial patterns. Robust stratigraphic frameworks are an integral part of these worldwide compilations. Bulk carbonate rock carbon isotope records are a widely used, and easy‐to‐generate, stratigraphic tool; it can substitute for biostratigraphy. However, inconsistencies in the amplitude and shape of stratigraphic carbon isotope patterns have also hampered the successful linkages of different geographic locations. In this study, we focus on the multicomponent nature of various limestone facies. We show how sampling strategies can be adapted in order to retrieve material from this multicomponent system that will most likely represent secular patterns in marine dissolved inorganic carbon δ13C. By obtaining multiple and randomly chosen bed‐internal samples, we reveal that the magnitude of bed‐internal δ13C variations can differ between distinct lithologies. However, we also note that the largest within‐bed variations (in excess of 0.5‰) do not correspond to obvious textural variations for this specific rock. Bed‐internal variations do not always trace marine dissolved inorganic carbon δ13C and might cause identification of ambiguous isotope stratigraphic markers that do not allude to globally correlative signals.