Proveniência e transporte sedimentar no sistema praia - duna frontal recente entre Itarema e Camocim (CE)

Abstract

The Cearáis west coast between the towns of Itarema and Camocim is a natural lab proper to study of the recent sedimentary provenance and transport on beaches and dunes. The presence of hydrodynamic and rocky obstacles and the strong effective action of the wind allow testing the pattern of continuity and inversion of the regional alongshore drift, and eolic grain-size sorting of beach sands and incipient foredunes. The presence of two major rivers (Acarai' and Coreaú), a park of wind power generation (Itarema, eastwards) and an area of environmental protection (Jericoacoara) highlight the relevance of this matter. This work evaluated the provenance and dynamics of marine and aeolian transport through the collection and analysis of recent beach sands (swash zone) and foredunes (crest) along the mentioned stretch. For the beach sands, the results for the entire range (100 km) is consistent with the regional alongshore drift westwards, typical of the Brazilian northern coast. At shorter intervals (up to few tens of kilometers), it was shown that physical blockage exerted by rocks prominences mild changes in the orientation of the coastline and drainages in the regional drift current is able to allow transport in the opposite direction by longitudinal currents that would otherwise be attenuated. The combination of vectors of the local alongshore drift indicate two areas that are susceptible to changes in the coastline: 1. Preá Beach, 10 km west of Barrinhas, in the beginning of Jericoacoara National Park, with erosive vocation; 2. East side of Guriú River, near the beginning of Tatajuba Beach, with depositional behavior. These areas correspond to locations where natural features of the alongshore drift, combined with the physiography of the coastline and hydrodynamics of tidal creeks act as modifier of the natural landscape in a timescale of years to decades. Regarding provenance, the heavy mineral analyses points to primary sources on metamorphic and plutonic rocks of the Médio Coreaú Domain, that are drained by the major rivers of the region. The secondary sources would be the Barreiras Formation and the adjacent continental shelf.