Moulton, M.A.B., Oliveira Filho, S.R., Rocha, T.B., Fernandez, G.B. 2013. Foredunes of Rio de Janeiro coast: genesis, structure and morphology. Proceedings 12th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 1319–1324, ISSN 0749-0208.-->
The formation of foredunes is one of the most important processes that occur during the evolution of the coastal sandy barriers, and can be observed along the coast of Rio de Janeiro State (Brazil) in both regressive, aggradational or transgressive barriers. The aim of this paper is to demonstrate the main processes of foredune development in areas with distinct patterns of coastal sand barriers along the Rio de Janeiro coast, subject to onshore and/or offshore winds. For this purpose we studied three areas in which foredunes present a representative morphology and show different types of coastal barrier. In each area, morphological aspects and foredune sedimentary structure where analyzed. Using total station and DGPS to generate 2D and 3D profiles, and a GPR antenna (400 MHz) to examine the sedimentary structure, an overall picture of the foredune formation process and the barrier type associated was made. The results showed that, foredunes developed on top of the regressive barrier (Atafona Beach) represent less than 2 m of sediment accumulated above the well-preserved beach ridges, suggesting that the main source of sediment supply comes from the river. In the aggradational barrier (Peró Beach) the intense aeolian transport (onshore winds) masks any sequence of beach signal, forming significant sequences of foredunes/blowouts (in this case sediment supply comes from the shoreface). The last area (Massambaba Beach), where winds blow offshore as result to the change of coastline orientation, we registered overwash deposits and occasionally foredune development on top of the transgressive barrier.