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VARIAÇÕES TEXTURAIS INDUZIDAS PELO VENTO NOS SEDIMENTOS DA FACE DA PRAIA (PRAIA DE ATALAIA, PIAUÍ)

1990; Sociedade Brasileira de Geologia; Volume: 20; Issue: 1 Linguagem: Inglês

10.25249/0375-7536.1990201207

ISSN

2177-4382

Autores

Abı́lio Carlos da Silva Pinto Bittencourt, José Maria Landim Domínguez, ORDÔNIO MOITA FILHO,

Resumo

ATALAIA BEACH, PIAUÍ.Sediment textural changes on the beach face of the Atalaia beach (city of Luís Correia, Piauí) result of the interaction of two different processes: 1. swash activity and 2. alternating dry and wet seasons.The last of these two processes was investigated in detail at lhe study area.During the dry season (August to December), onshore winds, with mean speads higher than 4.0 m/s, remove a significant portion of the fine to very fine sand size fraction of the beach face sediments, depositing it on the adjacent active dune fields.As a result, during this period beach face sands have high median values, averaging 0.700 mm.During the wet season (January to April) the uninterrupted rains damp the sediments.This in association with milder onshore winds inhibit the removal of the fine sediment fractions from the beach face.Thus, beach sands during this period are mostly composed by fine to very fine sand (about 90%) with mean values averaging 0.150 mm.Preservation in the strati graphic record of these climatic-produced textural changes depends on rates of shoreline progradation.Best chances of preservation are associated with high progradation rates.This research also shows that, in the study area, sediment supply to the dune field is closelly related to seasonal changes in atmospheric precipitation which are ultimately controlled by latitudinal shifts of the Intertropical Convergence Zone (ITCZ).Thus, climatic changes impeding the southward movement of the ITCZ during summer-fall will result in a significant decrease of precipitation over the study area, therefore increasing sediment transport from the beach face to the dune field.This will translate into a major expansion of the dune field.

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