Characterization of the sedimentary organic matter off the São Sebastião Island, on Southeastern Brazilian continental shelf using organic biomarkers

Abstract

The sedimentary organic matter provides a set of indicators that can be used to define the origin of the compounds, to obtain environmental reconstruction, and to understand the oceanographic and climatic processes. The Southeastern Brazilian Continental Shelf can be divided into two distinct zones of sedimentation and organic matter composition, due to the different hydrological processes that operate in this region. São Sebastião Island, northern coast of São Paulo, marks the boundary between these two areas, making São Sebastião area a convergence zone of sediment transport and a high sedimentation rate. Marine environments with a high sedimentation rate allow the achievement of high-resolution data. The combined use of different geochemical proxies, such as carbon stable isotopes and molecular organic markers, is an important tool in the study of the oceanographic and climatic changes in the past. Changes in the abundance and distribution of these compounds over the sediment cores can provide records of continental and marine paleoenvironments. This Project aims to use different geochemical proxies (carbon and nitrogen stable isotopes, n-alkanes, sterols and alkenones) to characterize the sedimentary organic matter in surface sediment samples and cores collected off São Sebastião Island in the Southeastern Brazilian Continental Shelf in order to evaluate the potential export of terrigenous material to the ocean and the implications of this contribution in the marine productivity. It also has the objective of associate of the characteristics of sedimentary organic matter with the water masses and carry out an assessment of temporal variability in the deposition of organic matter. (AU)