Caracterização geomorfológica e sedimentar de uma plataforma tropical: área Pirangi (Nordeste do Brasil)

Abstract

The advance on marine underwater research techniques has motivated many efforts aiming to detail and recognize the Continental Shelf features worldwide. The Brazilian tropical Continental Shelf specifically lacks information at this level, despite its importance, both for natural resources exploitation, as for marine conservation. This thesis, developed in the eastern Rio Grande do Norte Continental Shelf (Northeastern Brazil), uses new data acquired from hydroacoustic methods (singlebeam, multibeam and side scan sonars) and sedimentary samples, presenting a detailed analysis of the underwater landscape and sedimentary coverage. Combine biotic distribution patterns with abiotic information, enabling habitat classification for hard sea-bottoms at Pirangi area. This narrow and shallow shelf sector has a sharp division between the surface sediments that covers the inner (terrigenous) and external (biogenic) zones. Pointing out the sea level variations, ancient shorelines are preserved in four reef alignments (beachrocks), plus a palaeochannel formed during low sea-level periods, still conserved by the small sand supply. The sediment-starved shelf also presents wavy features, small submerged dunes composed by bioclastic gravel. The assembled evaluation of abiotic parameters and distribution pattern of benthic coverage, based on specific groups, allowed the individualization of habitats for reef surfaces, showing a habitat succession from coastal to offshore reefs. This analysis can be replicated to other Continental Shelf areas and contribute for management plans, for the necessary natural resources sustainable management, as well to the delimitation of marine conservation proposals.