Sedimentological aspects of northern continental slope of Rio Grande do Norte, NE of Brazil

Abstract

The continental slopes of north and northeast regions of Brazil lack data and knowledge and they represent an ecosystem of economic and environmental importance. The aim of this study is to assess the sedimentology of the continental slope of Potiguar Basin, NE Brazil. The samples were collected with box-corer and were analyzed for grain size, calcium carbonate content and organic matter content. Scanning electron microscopy and X-ray diffraction analysis were also conducted to know the sedimentary constituents of the samples. The sedimentary cover presents a grain size decreases as the depth increases, and it is represented by four sedimentary facies: silty, sandy silt, silty sand and sand with gravel. Calcium carbonate contents is moderated to high (37-93.2 %) and the content of organic matter is low (4.6-14.5 %). It is a mixed continental slope because the sediments are composed by siliciclastics and bioclasts. Quartz and Clay minerals are the main siliciclastics. Accessory minerals are Ilmenite, Zircon, Titanite, Muscovite, Biotite, Glauconite, Staurolite, Cordierite, Siderite, Rutile, Magnetite, Tourmaline, Pyrite, Monazite and Barite. Bioclasts are represented by bryozoans, sponges, foraminifera, annelid (Polychaeta tubes), nematodes, mollusks and diatoms. The presence of stable minerals (Zircon, Tourmaline and Rutile) indicates the contributions of Açu and Apodi rivers through their incised valleys and submarine canyons in the sedimentation of study area.