Origin of increased terrigenous supply to the NE South American continental margin during Heinrich Stadial 1 and the Younger Dryas

We investigate the redistribution of terrigenous materials in the northeastern (NE) South American continental margin during slowdown events of the Atlantic Meridional Overturning Circulation (AMOC). The compilation of stratigraphic data from 108 marine sediment cores collected across the western tropical Atlantic shows an extreme rise in sedimentation rates off the Parnaiba River mouth (about 2 degrees S) during Heinrich Stadial 1 (HS1,18-15 ka). Sediment core GeoB16206-1, raised offshore the Parnaiba River mouth, documents relatively constant Nd-143/Nd-144 values (expressed as epsilon(Nd(0))) throughout the last 30 ka. Whereas the homogeneous epsilon(Nd(0)) data support the input of fluvial sediments by the Parnaiba River from the same source area directly onshore, the increases in Fe/Ca, Al/Si and Rb/Sr during HS1 indicate a marked intensification of fluvial erosion in the Parnaiba River drainage basin. In contrast, the epsilon(Nd(0)) values from sediment core GeoB16224-1 collected off French Guiana (about 7 degrees N) suggest Amazon-sourced materials within the last 30 ka. We attribute the extremely high volume of terrigenous sediments deposited offshore the Parnaiba River mouth during HS1 to (i) an enhanced precipitation in the catchment region and (ii) a reduced North Brazil Current, which are both associated with a weakened AMOC. (C) 2015 Elsevier B.V. All rights reserved.