Sectorization of the Conceição Lagoon´s southern sector.

Abstract

The aim of this work is to propose a regionalization of southern Conceição Lagoon subsystem, located at the Santa Catarina Island - SC, based on its grain size, compositional and physiographic characteristics. The subsystem is part of a chocked lagoon, being connected to the remaining lagunar body by a narrow 3.5 m deep channel on its northern portion. It is surrounded by granitic rocks at west and by quaternary sedimentary deposits at east, north and south. Sediment samples were sampled at 16 regularly distributed points and were processed to determinate biodetritic carbonate, organic carbon content and conventional grain size parameters. Continuous surfaces of the variables were obtained through kriging interpolation. A bathymetric map resulted from the interpolation of 2.464 depth points digitalized from charts at the scale of 1:2.000 m. Individual sectors were identified based on data integration and spatial analysis of sedimentologic and bathymetric parameters. The integration of the variables through cluster analysis yielded the regionalization of the subsystem, were three depositional environments were defined: a predominantly sandy, a sand-muddy and a muddy environment. Besides these three, a fourth transitional environment situated between the banks and deeper areas was recognized. The muddy environment was subdivided in three distinct sub environments: deep muddy, sheltered muddy and organic muddy. Their limits were set through the analysis of the spatial behavior of sediment descriptors and bathymetry. From the results it is possible to conclude that the spatial and cluster analysis of morpho-sedimentological descriptors was efficient on the regionalization of the environment in study, even considering the small number of sediment samples.