Characterization of Nd Radiogenic Isotope Signatures in Sediments From the Southwestern Atlantic Margin

Based on radiogenic isotope systems of neodymium [Epsilon Neodymium-epsilon(Nd(0)), Nd-143/Nd-144, Sm-147/Nd-144, and Sm-Nd Depleted Mantle Model ages-T-DM] from current and previous data of continental rocks and associated sediments, this work provides the provenance of Holocene sediments from the Southwestern Atlantic Margin. The isotopic variability reported along the cores 7616 and 7620 are related to paleoceanographic and paleoclimatic changes. Further, we display the first Nd radiogenic isotope system distribution map of the study area. The map is the result of the principal component and clustering analyses of data compiled from the Ribeira belt, Luis Alves craton, and Parana basin rocks. Differences in Nd isotopic signatures allowed the distinction between the sediment sources of the cores. The Core 7616 exhibits epsilon(Nd(0)) average value of -10.5, T-DM = 1.4 Ga and Nd-143/Nd-144 = 0.512103, while the Core 7620 shows epsilon(Nd(0)) average value of -17.5, T-DM = 1.8 Ga and Nd-143/Nd-144 = 0.51177. The relative more radiogenic Nd ratios from the Core 7616 are associated to the contribution of sediments from the Parana basin, nevertheless less radiogenic values are observed along the Core 7616 between similar to 2,000 and 1,800 cal. yr BP. We have attributed the lower Nd ratios, recorded during this interval, to the decreasing influence from the Rio de la Plata estuary in the Core 7616. Remarkable less radiogenic Nd ratios are also recorded in the Core 7620 during the late Holocene. The intensification of the NE winds and the South America Summer Monsoon (SASM) enhanced the terrigenous input from the Paraiba do Sul River and southwards sediment transport by the Brazil Current (BC), providing higher contribution of less radiogenic metasediments from the Paraiba do Sul geotectonic domain to the Core 7620.