Effects of early marine diagenesis and site-specific depositional controls on carbonate-associated sulfate: Insights from paired S and O isotopic analyses

Carbon, sulfur and oxygen isotope profiles in Silurian strata of the Baltoscandian Basin (Estonia), coincident with Ireviken Bioevent, provide insights into basin-scale platform-specific depositional processes. Paired carbon records preserve a positive excursion during early Wenlock, faunal turnover, yet ?13C variability this compared to other locations within paleobasin reflects local influences superimposed on global signal. In comparison, do not systematic isotopic over same interval. Instead, have high sample-to-sample stratigraphic variability, particularly shallow-water carbonate rocks (scatter up ~10‰ for ?34SCAS ~ 25‰ ?34Spyr). This pattern is also found between sites from platform, where magnitude ?34Spyr differ depending relative sea level (and therefore facies). Such facies-dependent more closed- versus open-system diagenetic conditions pulses increased sedimentation rate shallow water environments generates greater both ?34Spyr. Increased reworking proximity shoreline results sulfide oxidation, seen as decrease most proximal settings. Platform-scale evolution isotopically distilled pore-fluids associated dolomitization deep Correlations paired ?34SCAS-?18OCAS data support these conclusions, demonstrating alteration CAS deposition marine diagenesis. We present framework assess sequence environmental processes that altered find ?34S ~27–28‰ approximates seawater sulfate. Our findings mechanism understand elevated many deep-time cannot otherwise be reconciled behavior sulfate reservoir.