Sediments and Quaternary Study of the Coastal Lagoon of Unare (Venezuela)

Roa Morales, Pedro; ,

Sediments and Quaternary Study of the Coastal Lagoon of Unare (Venezuela)

by Pedro Roa Morales, Univ Central de Venezuela, Caracas, Venezuela,

Document Type: Proceeding Paper

Part of: Coastal Zone '91

Abstract:

The coastal Lagoon of Unare is located in the N.E. of Venezuela (62? 12' - 65? 25' W/10? 04' - 10? 08' N), it is 26 km long and 6 km wide, 60 sq. km of surface in the rainy season, with a mean depth of 0.7 m, and is separated from the Caribbean Sea by a sand bar. Sedimentary evidence shows that it was formed in the Holocene, during the Flamenca transgression, approximately 5000 years B.P. The lagoon is surrounded at south by plains, in which black paleosoils from the Flamenca transgression that formerly reached 6-7 m a.s.l. were found, in 2-4 m depth excavations, rich in organic matter and containing fossils of Crassostrea sp., and gastropod Melongena melongena, sea urchins, corals, and foraminifers, revealing marine invasion; C-14 date analysis shows, ages of 3940-2170 years B.P. Studies on heavy minerals also give evidence of marine invasion; depositions carried on exclusively by the sea are covered by depositions of continental origin. Recently, a rise of the sea level was observed, causing a movement of the sand bar toward the continent, reducing the lagoon surface and affecting mangrove forests.

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