The Una and Bambuí Groups of northeastern and central Brazil are remnants of a vast intracratonic carbonate platform formed on the São Francisco Craton during the Ediacaran Period. Their basal stratigraphic units contain early phosphatic cements and phosphatic intraclasts in association with elongate digitate stromatolites in the more northern Irecê and Salitre paleobasins (Salitre Formation), and microbial laminites and aragonite crystal fan pseudomorphs in the more southern São Francisco paleobasin (Sete Lagoas Formation). Previous studies have drawn comparisons to other Precambrian phosphorites, as well as modern phosphogenetic environments, suggesting mechanisms of phosphogenesis dependent on the accumulation of porewater phosphate via microbial activity in low flow velocity environments, such as relatively quiescent tidal flats, where an absence of wave-driven advection and porewater refreshment could have allowed oversaturation with respect to carbonate fluorapatite. Here, we present new sedimentological data that characterize the depositional setting of the Salitre and Sete Lagoas formations as a shallow, wave-swept carbonate platform notable for its extensive high-energy lithofacies. In this setting, phosphatic and non-phosphatic stromatolite buildups formed within the same depositional facies, often in close (meter- and decimeter-scale) spatial association with one another. These data suggest that early phosphate mineralization of the Salitre and Sete Lagoas formations was likely not a function of low porewater advection in paleogeographically sheltered regions, but rather highly local processes of phosphate enrichment on a high-energy, wave-swept platform environment.

巴西东北部和中部的 Una 和 Bambuí 群是埃迪卡拉纪时期在圣弗朗西斯科克拉通形成的巨大克拉通内碳酸盐台地的遗迹。它们的基底地层单元包含早期的磷酸盐胶结物和磷酸盐碎屑，以及更北部的 Irecê 和 Salitre 古盆地（Salitre 组）中的细长指状叠层石，以及更南部的圣弗朗西斯科古盆地（Sete Lagoas 组）中的微生物叠层岩和文石扇形假晶质. 先前的研究已经与其他前寒武纪磷岩以及现代磷生成环境进行了比较，表明磷生成机制依赖于孔隙水磷酸盐在低流速环境（例如相对静止的潮滩）中通过微生物活动的积累，在没有波浪驱动的平流和孔隙水更新的情况下，碳酸盐氟磷灰石可能会过饱和。在这里，我们提供了新的沉积学数据，这些数据将 Salitre 和 Sete Lagoas 地层的沉积环境表征为一个浅层、波浪扫掠的碳酸盐平台，以其广泛的高能岩相而著称。在这种情况下，磷酸盐和非磷酸盐叠层石堆积物在同一沉积相内形成，通常彼此紧密（米级和分米级）空间关联。这些数据表明，Salitre 和 Sete Lagoas 地层的早期磷酸盐矿化可能不是古地理遮蔽地区低孔隙水平流的函数，而是高能量、