Late-Holocene paleoreconstruction of the Southwestern Atlantic Ocean: A multiproxy understanding of the paleoclimatic, paleoproductivity and paleotemperature variability

A multiproxy evaluation focusing on sedimentological, molecular, and isotopic proxies was used to reconstruct the environmental changes on the SW Atlantic Ocean margin enabling an integrated assessment of this basin’s Late-Holocene oceanographic and climatic dynamics. Variations in paleoproductivity, climate, and sea surface temperature (SST) indicate three phases throughout the core. The first phase (2800–1600 cal yr BP) showed a generally low marine and terrigenous organic matter input, marked by terrigenous material input pulses transported by the Brazil Current (BC) from small rivers of the South Brazil Bight (SBB) and/or Paraiba do Sul River. The second interval (1600–1300 cal yr BP) registered the lowest levels of fine sediments, total organic carbon content, and concentrations of all analyzed lipid biomarkers, indicating the occurrence of a semi-stationary meander of the BC that hindered the sedimentation of fine sediments. This phase may indicate a varied timing and duration due to the sparsed radiocarbon data. The third interval (1300 cal yr BP to modern years) presented the highest levels of marine and terrigenous proxies and were influenced by the strengthening of the South America Monson System (SAMS), the El Niño Southern Oscillation (ENSO) events, and the NE winds, which caused higher precipitation in the La Plata River drainage basin. A northward displacement of the Brazil Coastal Current (BCC) and the transport of the Plata Plume Water (PPW) to the central regions of the SBB, as well as the occurrence of more regular upwelling events may also influence the sedimentary organic matter composition. SST showed a variation up to ~3.2°C through the core and was related to the influence of the BC current associated with the Tropical Water (TW) and the South Atlantic Central Water (SACW), and the PPW influence on the shelf.