Geochemical biomarkers of recent and paleoenvironmental processes in the Caravelas Estuary, BA, Brazil: implications to validate the geolipid sedimentary record

Abstract

Although only a small fraction of the organic matter is preserved in the sedimentary record, it provides a variety of proxies, including molecular biomarkers, which provide important information about the environmental conditions under which it was produced and deposited. This proposal aims to determine the origin, distribution and preservation status of lipid biomarkers in modern surface sediments of the Caravelas estuary, depending on environmental factors and oceanographic conditions. Also, evaluate variations in the chronostratigraphic record associated with historical changes in biomarkers origin, depositional conditions and diagenetic alterations as a way to weigh the status of the geolipid sedimentary record and its suitability for paleoenvironmental reconstructions in this region. The region of Caravelas is one of the oldest urbanized areas on the northeastern Brazilian coast, has been subjected to impacts of various human activities and presented a large urban and industrial growth in the last 40 years. Analysis of lipid biomarkers (aliphatic hydrocarbons, steroids and alkenones) and the isotopic signature (´13C) of n-alkanes will be performed in 30 surface sediment samples and two sediment cores. Surface and core sediment samples were collected during 2008 using a box-corer and a vibra-corer, respectively. Compound identification and quantification will be performed with GC-FID and GC-MS for confirmation, while the isotopic signature of n-alkanes will be analysed with GC-IRMS. This research proposal aims to contribute to the understanding of the recent and historical processes that influence the distribution and preservation of organic matter in a portion of the Brazilian continental margin particularly poorly known.