The Capitan Reef Complex in West Texas is famous for its high prevalence of early marine cements, unusual for a Phanerozoic platform, leading some to suggest that Precambrian styles of carbonate sedimentation enjoyed a Permian encore. Here, we use patterns of stable Ca, Mg, C and S isotopes to better understand the environmental driver(s) of the enigmatic cementation. We find that calcite that is the most enriched in ⁴⁴Ca has δ³⁴S values that approach the inferred composition of Permian seawater sulfate. Microbial sulfate reduction in pore fluids must have been spatially and temporally coincident with recrystallization of primary carbonate phases, such that substantial ³⁴S-enriched sulfate was incorporated into diagenetic calcite under relatively closed-system conditions. Moreover, the magnitude of ³⁴S-enrichment of carbonates relative to seawater was strongly influenced by local diagenetic conditions, with fluid-buffered early marine cements, shelf, reef, and upper slope preserving more seawater-like S isotope ratios than the more sediment-buffered lower slope. Some samples are far more ³⁴S-enriched relative to seawater than those from modern sites in similar depositional environments, possibly responding to specific combinations of sedimentary parameters (e.g., grain size, porosity, organic matter rain rate). Additionally, the sulfate concentration in the Delaware Basin might have been slightly lower than modern levels, leading to more extensive isotopic evolution of sulfate in pore waters during carbonate recrystallization. Based on the data and a numerical model of carbonate recrystallization, we suggest that one driver of the extensive seafloor cement precipitation in the Capitan Reef Complex was a Permian water column [Ca²⁺]:[SO₄²⁻] ratio somewhere between 1 and modern seawater.

德克萨斯州西部的卡皮坦礁复合体以其早期海相胶结物的普遍存在而闻名，这对于显生宙平台来说是不寻常的，这导致一些人认为前寒武纪的碳酸盐沉积风格经历了二叠纪的重演。在这里，我们使用稳定的 Ca、Mg、C 和 S 同位素模式来更好地了解神秘胶结的环境驱动因素。我们发现，富含⁴⁴ Ca 的方解石的 δ ³⁴ S 值接近推断的二叠纪海水硫酸盐成分。孔隙流体中的微生物硫酸盐还原必须在空间和时间上与初级碳酸盐相的重结晶一致，因此大量³⁴在相对封闭的系统条件下，富硫硫酸盐被掺入成岩方解石中。此外，碳酸盐相对于海水的³⁴ S 富集程度受到当地成岩条件的强烈影响，流体缓冲的早期海相胶结物、陆架、礁石和上斜坡比沉积物更多地保留了类似海水的 S 同位素比。缓冲下坡。有些样本远不止³⁴与来自类似沉积环境的现代遗址相比，相对于海水富含硫，这可能与沉积参数的特定组合（例如，粒度、孔隙度、有机质降雨率）有关。此外，特拉华盆地的硫酸盐浓度可能略低于现代水平，导致碳酸盐重结晶过程中孔隙水中的硫酸盐同位素演化更为广泛。基于碳酸盐重结晶的数据和数值模型，我们认为，在 Capitan Reef 复合体中广泛的海底水泥沉淀的一个驱动因素是二叠纪水柱 [Ca ²⁺ ]:[SO ₄ ^2- ] 比率介于 1 和现代海水。