Evolution of the coastal barrier-lagoon system offshore Cabo-Frio - Rio de Campos (E-Brazil) during the late Quaternary transgression

Coastal barrier-lagoon systems are dynamic environments of great economic and ecological importance, but also of great sensitivity to climate change and sea level rise. The continental shelf offshore East Brazil is relatively poorly studied, which prevents detailed reconstruction of the geomorphologic development during the late Pleistocene-Holocene transgression. Here we present a morphologic and stratigraphic analysis of the Late Quaternary barrier-lagoon systems offshore Cabo Frio and Rio de Campos, using 150 km of high resolution seismic data (Parasound echosounder) and Multibeam bathymetry (Kongsberg EM 710), as well as intermittent core sampling acquired during cruise M125 by the research vessel Meteor in March/April 2016. The broad (~80 km) continental shelf has a low depth gradient, high wave energy and is sediment starved. At present, sedimentation is strongly drift dominated, with mostly bioclastic outer shelf and siliciclastic inner shelf deposition. The main morphological features include several relict barriers along most of the shelf, aligned over at least three levels in a bathymetric range from 60 to 85 m depth. The stratigraphy is characterized by a recent thin sandy drape overlying several seismo-stratigraphic units representing coastal prograding wedges, coastal barriers and broad back-barrier lagoon and/or channel systems. The back-stepping of river channel deposits is overlain by coastal back-barrier lagoon deposits, following sea level rise. This observation indicates that the stratigraphic evolution of the shelf was dominated by a late Pleistocene - Holocene transgressive ravinement. The interplay between the rate of sea level rise, the geomorphologic setting and the preservation potential of former shorelines, is compatible with the current coastal morphology of the on-land area. The evolution of such submerged coastal systems is compared to other submerged settings studied worldwide with the scope of improving late Quaternary sea level rise models.