Reconstruction of Past Environmental Variations in the Semi-Arid Brazilian Nordeste Through Last Interglacials

Summary Brazilian Nordeste is a semi-arid region that is a key area for future South American climate. Climatic conditions of Nordeste strongly depends on nearby western Atlantic parameters (Temperature, Salinity, etc.). This work aims to improve the understanding of the Nordeste response to hydroclimate and vegetation changes over past interglacial periods (known as odd Marine Isotope Stage, MIS) based on a 17 m long marine sedimentary core (GL1180) collected on the eastern Brazilian continental margin. A multi-proxy approach will be developed by analyzing sedimentary organic matter (OM) at the bulk and molecular levels. Here we present the first results of bulk OM analysis for 135 selected depths with a higher temporal resolution during interglacial periods. Bulk elemental and isotope analyses of OM in sediments from the GL1180 core revealed that the Brazilian Nordeste area experienced notable changes in humidity conditions over the last 300 kyr BP. Complementary lipid biomarker analyses of these samples are in progress to help in the reconstruction of past vegetation and hydroclimate conditions in northeastern Brazil.