Unraveling Ordovician-Silurian sedimentation: Facies, paleocurrents, and architectural analysis of the Tacaratu Formation, Northern Tucano Sub-basin, Brazil

This study investigates the sedimentary record of the Ordovician-Silurian Tacaratu Formation in the Northern Tucano Sub-basin, Brazil, with a focus on facies, facies associations, architectural elements and paleocurrents. The Tacaratu Formation represents the basal Paleozoic interval of the Northern Tucano and Jatoba<acute accent> sub-basins, predominantly composed of coarse-grained siliciclastic deposits associated with braided fluvial systems. Detailed fieldwork at 10 localities into the Northern Tucano sub-basin was conducted to analyze facies, geometry, bounding surfaces, and paleocurrents, aiming to provide new insights into sedimentary processes and depositional controls that shaped its formation. Eleven facies were identified, grouped into four main facies associations: FA1 - gravel and sandy bars, FA2 - sandy bars and bar tops, FA3 - coarse-grained middle channel bars, and FA4 - overbank fines. Paleocurrent analysis revealed a predominant northward paleoflow trend, aligning with previous studies, but also indicated variations suggestive of low-sinuosity wandering channel morphologies previously interpreted as braided. These findings contribute to a deeper understanding of sedimentary processes and depositional controls in the Tacaratu Formation, offering new perspectives on the early fluvial systems of the Western Gondwana.