Morfologia e análise da sucessão deposicional do vale inciso Quaternário de Marapanim, Norte do Brasil.

Abstract

The coastal sector located eastward of the Amazon river mouth is characterized by several estuarine systems, that harbor large mangrove areas with approximately 7600 km2. The Marapanim Estuary is influenced by macrotidal regime with moderate waves influence. The morphological and morphostratigraphic aspects were investigated by using remote sensing images (i.e., Landsat-7 ETM+, RADARSAT- 1 Wide and SRTM) integrated with bathymetric and surface sediments data. Facies analysis of quaternary deposits was studied based on cores collected by vibracore and rammkersonde systems. These deposits were dating by AMSradiocarbon. The estuary was compartmentalized into estuary mouth, estuary funnel, and upstream estuary. The open-mouthed estuary (inner, middle and outer) is influenced by a mixedenergy in which both waves and macrotides play an important role in the hydrodynamic control, and transport and sediment. The data integration reflects an evolutive model of estuarine incised valley fill, defined by a basal surface that limits Quaternary deposits from Tertiary one, which are recovered by fluvial sands that constitute the lowstand system tract. The initial stage of the last transgression provided the trapping of fluvial sediments within the valley. Later, a transgressivemud deposits migrated over fluvial sediments to landward. Under stillstand sea level occurs widedevelopment of mud flat (freshwater swamp and mangroves), as well as its progradation toward the estuary mouth. Also, occur a transgressive pulse responsible for sandy deposits (beaches and dunes) that recover muddy deposits and provide the migration of this deposit to the elevated topographic level. The geological model proposed has application for the northeast coast of Pará, characterized by estuarine systems resulted by the last Holocene transgression.