Carbon, sulfur and oxygen isotope profiles in Silurian strata of the Baltoscandian Basin (Estonia), coincident with the Ireviken Bioevent, provide insights into basin-scale and platform-specific depositional processes. Paired carbon isotope records preserve a positive isotope excursion during the early Wenlock, coincident with faunal turnover, yet δ¹³C variability of this excursion compared to other locations within the paleobasin reflects local depositional influences superimposed on a global signal. In comparison, sulfur isotope records do not preserve a systematic isotopic excursion over the same interval. Instead, sulfur isotope records have high sample-to-sample stratigraphic variability, particularly in shallow-water carbonate rocks (scatter up to ~10‰ for δ³⁴S_CAS and ~ 25‰ for δ³⁴S_pyr). This pattern of isotopic variability is also found between sites from the same carbonate platform, where the magnitude and isotopic variability in δ³⁴S_CAS and δ³⁴S_pyr differ depending on relative local sea level (and therefore facies). Such facies-dependent variability reflects more closed- versus more open-system diagenetic conditions where pulses of increased sedimentation rate in the shallow water environments generates greater isotopic variability in both δ³⁴S_CAS and δ³⁴S_pyr. Increased reworking and proximity to the shoreline results in local sulfide oxidation, seen as a decrease in δ³⁴S_CAS in the most proximal settings. Platform-scale evolution of isotopically distilled pore-fluids associated with dolomitization results in increased δ³⁴S_CAS in deep water settings. Correlations in paired δ³⁴S_CAS-δ¹⁸O_CAS data support these conclusions, demonstrating the local alteration of CAS during deposition and early marine diagenesis. We present a framework to assess the sequence of diagenetic and depositional environmental processes that have altered δ³⁴S_CAS and find that δ³⁴S of ~27–28‰ approximates Silurian seawater sulfate. Our findings provide a mechanism to understand the elevated variability in many deep-time δ³⁴S_CAS records that cannot otherwise be reconciled with behavior of the marine sulfate reservoir.

Baltoscandian 盆地（爱沙尼亚）志留系地层中的碳、硫和氧同位素剖面与 Ireviken 生物事件同时发生，提供了对盆地规模和特定平台沉积过程的深入了解。成对的碳同位素记录在早期文洛克期间保留了正同位素偏移，与动物群更替一致，但与古盆地内其他位置相比，这种偏移的δ ¹³ C 变异性反映了叠加在全球信号上的局部沉积影响。相比之下，硫同位素记录并没有在同一时间间隔内保存系统的同位素偏移。相反，硫同位素记录具有较高的样品间地层变异性，特别是在浅水碳酸盐岩中（δ ³⁴ S _{CAS 的}散射高达 ~10‰δ ³⁴ S _pyr约 25‰ )。这种同位素变异模式也出现在来自同一碳酸盐平台的站点之间，其中 δ ³⁴ S _CAS和 δ ³⁴ S _pyr的量级和同位素变异性因当地相对海平面（以及相）而异。这种依赖于相的变异性反映了更封闭的系统与更开放的系统成岩条件，其中浅水环境中沉积速率增加的脉冲在 δ ³⁴ S _CAS和 δ ³⁴ S _{pyr 中}产生更大的同位素变异性. 增加再加工和靠近海岸线会导致局部硫化物氧化，这被视为最近环境中 δ ³⁴ S _CAS的减少。与白云石化相关的同位素蒸馏孔隙流体的平台级演化导致深水环境中δ ³⁴ S _CAS增加。δ ³⁴ S _CAS -δ ¹⁸ O _CAS数据的相关性支持了这些结论，证明了 CAS 在沉积和早期海洋成岩过程中的局部改变。我们提出了一个框架来评估改变 δ ³⁴ S _CAS的成岩和沉积环境过程的序列并发现~27–28‰ 的δ ³⁴ S 接近志留纪海水硫酸盐。我们的研究结果提供了一种机制来理解许多深时 δ ³⁴ S _CAS记录中升高的变异性，否则无法与海洋硫酸盐储层的行为相协调。