The Vaza-Barris River: A late Quaternary decoupled accumulation-erosion model for rivers of the NE Brazil Atlantic passive margin

Abstract

Limited insight is available regarding the links between the upstream-downstream fluvial response to climate changes and alluvial-coastal base-level factors in the passive Atlantic margin of tropical South America. This work attempts to characterize the last glacial-interglacial fluvial response of a typical semi-arid Brazilian Northeast River that drains Central-East Brazil's highlands. We integrate the full extension of the Vaza-Barris River alluvial plain record with the alluvial-coastal plain subsurface record. We used digital elevation models, satellite imagery, cores drill description, high-resolution seismic data, optical luminescence, and AMS 14C dating of alluvial terraces Five terrace levels, in the upstream provinces, and three terrace levels in the Coastal-alluvial province were identified. In the continental margin adjacent to the Vaza-Barris river-mouth, incised-valleys in the coastal shelf. Morphosedimentary proxies indicate that periods of aggradation and incision alternated during the late Quaternary due to different inland and eustatic dominant factors. We also estimate that the estuary stored a sediment fill of approximately ∼55 m since the late Pleistocene,. Thus, climate change and sea-level variations differentially controlled the fluvial response and the morphology of the adjacent continental margin along the fluvial system. The decoupled accumulation/erosion upstream-downstream patterns can be used as a model to be tested in fluvial systems of the passive margin of the Brazilian Northeast.