A GÊNESE DE CRISTAS DE PRAIAS E DUNAS FRONTAIS
Abstract
A origem de cristas praiais (beach ridges, cristas de praia) formadas em ambiente de mar aberto e de micromarés na costa australiana é revisada. Na literatura clássica, existem três teorias principais sobre a evolução dessas formas, duas sugerindo uma origem marinha, outra uma origem eólica. São apresentados dados relativos à evolução moderna de cristas de praia e dunas frontais incipientes nas regiões de Myall Lakes e Cervantes, que apóiam fortemente a hipótese de origem eólica. As dunas frontais incipientes formam-se a partir de uma diversidade de processos que conduzem à construção de rampas, terraços ou cristas, em função de taxas de progradação, tipos de cobertura vegetal, transporte de sedimentos e balanço dos processos erosivos.
Palavras chave: dunas frontais, cristas de praia, evolução de praias.
ABSTRACT
The genesis of sand “beach ridges” formed on openocean, microtidal Australian coasts is reviewed. Three major theories of evolution have been proposed, one suggesting a marine origine, the other an aeolian origin. Data are presented on the mordern evolution of “beach ridges” and incipient foredunes at Myall Lakes, NSW, and Cervantes, WA, which strongly supports an aeolian genesis. Incipient foredunes may be initiated in a variety of ways leading to the formation of ramps, terraces or ridges depending on progradation rates, vegetation type and cover, sediment transport rates and scale of erosional processes.
Key words: foredunes, beach ridges, beachs evolution
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