Portal de Periódicos da CAPES

As flutuações de nível do mar durante o quaternário superior e a evolução geológica de "deltas" brasileiros

1993; Issue: 15 Linguagem: Inglês

10.11606/issn.2317-8078.v0i15p01-186

2317-8078

L. Martin, Kenitiro Suguío, J.M. Flexor,

Coastal and Marine Management

Along the Brazilian coast, there are several extensive progradation areas, frequently related to important river mouths, while others don't have any relationship with present or past river mouths. All the studied cases, up to that time, can be explained through the paleogeographic evolutionary model conceived by the authors, valid for the sector from Macao (State of Rio de Janeiro) to Maceió (State of Alagoas). Two or more stades from the most complete model can be omitted to explain the evolutionary history of some of these coastal plains. The coastal plains associated to the Doce (State of Espirito Santo) and Paraíba do Sul (State of Rio de Janeiro) rivers are the most important, being characterized by expressive lagoonal deltas constructed within large paleolagoons. The coastal plains of the Jequitinhonha (State of Bahia) and São Francisco (States of Sergipe/Alagoas) rivers don't exhibit intralagoonal deltas, because they never developed extensive paleolagoons during their geological evolution. On the other hand, the Paraíba river mouth (State of Piauí/Maranhão) could be assumed as an essentially wind-dominated coastal plain, and the Caravelas (State of Bahia) coastal plain doesn't have relationship with any river mouth. These coastal plains have been before considered as essentially Halocene in age, but there are Pleistocene and Holocene deposits. Moreover, the Quaternary relative sea-level changes, completely ignored in some countries to explain this type of coastal plains, played an essential role in the Brazilian coast. Finally, considering the sensu strictu definition of delta, even the coastal plains associated with river mouths could not be assumed as true deltas, because their sediments were only partially supplied by the rivers. The understanding of geological evolution of these coastal plains, during the last millenia, supply us with useful information about the paleoenvironmental changes, as well as, with possible explanations about the present dynamics in terms of erosion and sedimentation. Therefore, could be useful to solve many problems, like that related with accelerated erosion and sedimentation, with or without anthropic influence, in coastal management.