Quaternary sea-level history and variation in dynamics along the Central brazilian coast : consequences on coastal plain construction

1996

Article

Martin Louis, Suguio K., Flexor J.M., Dominguez J.M.L., Bittencourt A.C.S.P.

Anais da Academia Brasileira de Ciencias, 1996, 68 (3), p. 303-354

The central part of the Brazilian coast experienced considerable relative sea-level fluctuations during the Quaternary. It has been possible to identify three high marine levels. The last two, during which the sea-level was at a maxium 8 + or - 2 m (123,000 yr BP) and 4.8 + or - 0.5 m (5,100 yr BP) above the current level, have left substantial records, whose identification was possible due to numerous absolute datings. This sea-level history had a profound effect on the evolution of sedimentary plains. Wave energy, tidal range and river loads, for example, have been considered as the most important factors in the classical models of coastal sedimentation. However, the role played by relative sea-level changes has been not much considered. Probably, this is due to the fact that the models have been proposed by authors from the northern hemisphere countries, where most commonly the present sea-level is the highest during the Holocene time. This is not the case of Brazil, where most part of the coast was submerged until 5,100 yr BP followed by emergence up today, abstracting two quick oscillations. Obviously, the coastal dynamics could not be the same during relative sea-level rise or sea-level drop. The equilibrium profile of a sandy coast will be destroyed with sea-level changes and its restoration will be accompanied by transfer of sands, from backshore and adjacent land areas to foreshore during sea-level rise and from foreshore to backshore during sea-level drop. During submergence periods (relative sea-level rise), barrier-island/lagoonal systems are dominant and the rivers could reach protected areas, as lagoons and estuaries, to build deltas. In contrast, a sea-level fall creates highly unfavourable conditions for the genesis and maintenance of barrier island/lagoonal systems. Lagoons and bays become emergent and beach-ridge plains rapidly prograde, resulting in regressive sand sheet... (D'après résumé d'auteur)

Géologie du quaternaire [064GEOQUA]

QUATERNAIRE ; ZONE COTIERE ; NIVEAU MARIN ; VARIATION TEMPORELLE ; SEDIMENTATION LITTORALE ; TRANSGRESSION ; PALEOENVIRONNEMENT

BRESIL

Fonds IRD [F B010014988]

fdi:010014988