Morphological and sedimentary patterns of a semi-arid shelf, Northeast Brazil

Abstract

The semi-arid shelf of Northeastern Brazil, adjacent to the State of Ceará, was analyzed using high-resolution seismic imaging, side-scan sonar imaging, sedimentary patterns, remotely operated vehicle (ROV), scuba dive surveys, and satellite images. Three geomorphic sectors were found according to physiographic, sedimentological, and morphological aspects: Coreaú, Mundaú, and Jaguaribe. The Ceará shelf is characterized by a mixed sedimentological pattern including a significant modern carbonate supply, relict siliciclastic grains, and a mixing of carbonates and siliciclastics. The modern siliciclastic supply is concentrated near the coast (shoreface/shoaling zone) and solid discharge from rivers is low due to a semi-arid climate. The subaqueous features (dunes, ripples, reefs, beachrocks, and incised valleys), both relict and modern, formed both as a result of sea-level changes (Wisconsin Glacial and Holocene transgression) and modern processes (longshore and wind-driven currents, waves, and tides).