Physical and geochemical properties of centennial marine sediments of the continental shelf of southeast Brazil

Abstract

Studies associated with the physical properties of marine sediments are being increasingly disseminated around the world. Comparing these geophysical parameters with sedimentological analysis allows several correlations of the core collected in a region. This research combines sedimentological information of cores samples with geophysical and geochemical properties to identify the influence of organic matter and sediment texture on the characteristics and depositional dynamic. The sediment cores were collected using a box core in four stations of the mud facies from the Cabo Frio shelf, Brazil. Geophysical properties were acquired using the MSCL (multi-sensor core logger). The wave velocity, porosity, density, sediment texture, and organic content have been conducted in samples collected in the shelf mud. The physical properties helped to distinguish two groups, according to oceanographic and sedimentological patterns within the same depositional system. The first group was characterized by the presence of silty sand and high P-wave velocity (nearshore and offshore core) and the second group by the predominance of silt, high organic input, and porosity (the intermediate cores). The presence of coarser sediments in the first group indicates the contribution of terrigenous sediment carried by coastal currents. The second group presents the same deposition dynamic with high accumulation of fine particles and organic carbon, indicating the domain of high productivity upwelling currents and oceanic vortices. Keywords: P-wave, grain size; porosity, organic carbon.