Comparative Paleoenvironmental Evolution of the Araripe and Parnaba Basins: Evidence of Interbasinal Connectivity and Marine Ingressions During the Alagoas Stage

The Alagoas local Stage (Aptian – lower Albian) records the final rifting phases of the South Atlantic and is characterized by complex sedimentary successions. This study presents a comparative analysis of the Araripe and Parnaíba basins (Northeastern Brazil), focusing on the high degree of similarity in their paleoenvironmental evolution. We explore how parallel successions of lacustrine, evaporitic, and marine-influenced facies indicate synchronized paleoclimatic conditions and potential physical connectivity between these inland sag systems, specifically during the late Alagoas Stage. The research integrated ostracod biostratigraphy/paleoecology and organic faciology across key reference sections, specifically wells 2-CO-1-MA, 1-UN-32-PI and 1-UN-24-PI in the Parnaíba Basin, and wells 2-AB-1-CE and 2-AP-2-CE in the Araripe Basin. The results reveals a shared stratigraphic architecture, characterized by specific ostracod assemblages of the Pattersoncypris spp. and Damonella? grandienses biozones. The succession evolves from fluvial-lacustrine systems into restricted, hypersaline environments. A significant regional marker identified is a widespread evaporitic interval (Ipubi and middle Codó formations) occurring within the same ostracod subzone (Pattersoncypris crepata) in both basins. Organic facies analysis indicates intervals of high primary productivity and preservation associated with stratified water columns and identical trends in organic matter types. A major focus of this investigation is the subsequent transition to marine-influenced facies, most notably within the Romualdo Formation, Araripe Basin. Ongoing research has provided critical evidence of marine ingressions characterized by specific organic facies and microfossil assemblages that are mirrored in the Parnaíba Basin. The syn-chronicity of these events suggests that both basins were not only subject to the same regional paleo-climatic fluctuations and paleoecological pressures but were also intermittently connected to the evolving Equatorial South Atlantic during maximum flooding events. The remarkable mirroring of paleoenvironmental phases, culminating in the marine-influenced Romualdo Formation, suggests a strong regional overprint. The convergence of ostracod bioevents, organic facies trends, and marine markers points to a unified paleogeographic evolution, supporting the hypothesis that these basins were not isolated. This integrated model provides a robust framework for refining chronostratigraphic correlations and understanding the stratigraphic development of the Ap-tian-Albian across the Brazilian Equatorial Margin. The authors gratefully acknowledge the support and funding from TotalEnergies.