Análise sedimentológica da plataforma continental, foz, talude e cânions do Estado do Espírito Santo – Brasil

Abstract

The Espirito Santo State´s submerged marine area is composed of the Espirito Santo Basin and the northern portion of Campos basin, which are two outstanding reservoirs of marine mineral resources, being very important for the country´s economy. Based on this premise, this study aims to define the sedimentology of this region, comprising continental shelf, Doce River’s mouth, slope, and Watu Norte and Doce canyons, as to their granulometry, calcium carbonate contents and organic matter, and then to analyze changes in these parameters’ pattern between the rainy and dry seasons. To this end, a new approach to the methodology was addressed by making use of three replicates of sediment samples for each point in the sampling framework. Laboratory analyses were carried out by such methods as sieving, pipetting, calcination and measurements with a modified Bernard calcimeter for sediment samples taken out during Petrobras campaigns in periods of summer and winter. The data were interpreted by maps that were created with “ArcView 8.3” software and statistically compared through a Microsoft Excel 2010 Program . The study area presented a granulometry ranging from fine silt to coarse sand, for which the largest fields of muddy sediments were found on the continental slope, and those with coarser grain sizes stayed nearer the coast in the continental shelf. The continental slope further concentrated the highest contents in calcium carbonate and organic matter. The sediments pattern along the year had its widest variations on the Doce River’s mouth and in the continental shelf, whereas in the slope that pattern was not found to change. As concerns the analysis of the sampling points in triplicates, it was concluded that, despite its improving the accuracy of data estimates, it proved to be needless given the effort involved in data collecting and analyzing, and the fact that in the majority of points those triplicates yielded low values of the standard deviation.