Grain-size signatures reveal the complexity of seafloor processes in the Santos bifurcation area (Southwestern Atlantic Margin)
DOI:
https://doi.org/10.1590/2675-2824073.25182Palavras-chave:
Grain size, End member, CM diagram, Continental slope, Santos BasinResumo
The Southern Santos Basin (Southwestern Atlantic margin) is characterized by the Santos Bifurcation (SB), where the intermediate South Equatorial Current splits into northward (Intermediate Western Boundary Current) and southward (Brazil Current) branches. Despite previous studies on sediment dynamics north of 24°S, there is a lack of knowledge about the southern sector. This study investigates grain-size variability in 19 sediment cores from the continental slope, here divided into shallow (from the shelf break to 600 m), middle (600-1400 m), and deep (1400-2000 m) sectors. Using CM diagrams and end-member analysis, we identified three distinct sediment transport modes: (1) shallow sediments, dominated by coarser fractions (very fine sand) and graded suspension, linked to Brazil Current influence; (2) middle and deep sediments; finer (silt-dominated) and deposited via uniform and pelagic suspension, reflecting weaker hydrodynamic conditions near the SB; and (3) localized turbidite deposits in the middle sector, evidenced by anomalously high coarse fractions. These findings highlight a bathymetric control on sediment distribution, with hydrodynamic regimes shaping depositional processes. The study provides new insights into sediment transport dynamics in the understudied southern Santos Basin, confirming the interplay of contouritic and gravitational processes in the region.
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