CHARACTERIZATION AND GEOCHRONOLOGY OF THE DELTAIC SYSTEM FROM JEQUITINHONHA RIVER, BRAZIL.

Deltaic systems possess singular morphology and represent a portion of the Brazilian large fluvial systems, with complex dynamics and mouths located at the Atlantic Ocean. Landscapes generated are occupied by diverse human activities over the coast and depend on a certain degree of dynamic equilibrium to its maintenance. The mouth of Jequitinhonha River, located at the extreme South of Bahia state, has suffered great transformations over the last decades, causing coastal erosion processes due to fluvial discharge reduction, thus changing the local dynamic. So, to understand the preterit deltaic dynamic and the possible agents of the current changes, we proposed an approach utilizing grain size and Optically Stimulated Luminescence (OSL) of the deposits by the river mouth, with the processes currently demonstrated. The main results point to mixed depositional environment over the sampling points and additionally in depths, demonstrating cyclicity of depositional agents and energy. Depositional ages obtained were 2.72 ± 0.23 (Ky) for the left riverbank, 1.1 ± 0.15 (Ky) for the right riverbank, and the youngest deposit located at the front island, with absolute dating of 0.555 ± 0.065 (Ky). The results evidence a tendency of coastal progradation during the last thousands of years, prior to anthropic interventions which diminished and regulated fluvial discharge of Jequitinhonha River, resulting in advancement of local coastal erosive processes. [ABSTRACT FROM AUTHOR]