Anomalous terrigenous input to the continental margin of tropical western South Atlantic at the Pleistocene-Holocene transition

Continental slopes off southeastern Brazil preserve key records of terrigenous sediment transfer during the last deglaciation, yet the processes controlling these deposits remain poorly constrained. Here, we analyse four sediment cores to investigate the origin of a distinct terrigenous-rich layer (TM facies) identified across all records. Sedimentological, inorganic geochemical, and geochronological data were integrated to reconstruct the depositional history of this interval. The results show a marked increase in sedimentation rates and in ln(Fe/Ca), ln(Ti/Ca), and ln(Al/Si) ratios between ~ 13 and 8.0 cal ka BP, indicating increased input of fine terrigenous material. This interval is not observed elsewhere in the records, suggesting specific paleoenvironmental conditions during its formation. We interpret the TM facies as the result of remobilization of sediments previously stored on the outer continental shelf and transported downslope during late deglacial sea-level rise. Although precipitation increased in northeastern Brazil during Heinrich Stadial 1 and the Younger Dryas, paleoclimate records indicate no substantial increase over southeastern Brazil. Thus, enhanced fluvial discharge is unlikely to explain the observed pattern. Instead, progressive flooding of the Abrolhos Shelf reestablished shelf–slope connectivity, promoting sediment remobilization. The sedimentary response to this eustatic forcing was likely conditioned by the local geomorphological context, which favored sediment storage on the continental shelf during lowstands and subsequent shelf–slope connectivity during the last post-LGM marine transgression. These results indicate that eustatic forcing was the primary control on terrigenous deposition, with climate playing a secondary role.