01 Jun 2021

01 Jun 2021

Review status: this preprint is currently under review for the journal OS.

New insights of the influence of ocean circulation on the sedimentary distribution in the Southwestern Atlantic margin (23° S to 55° S) based on Nd and Pb isotopic fingerprinting

Michel Michaelovitch de Mahiques1,2, Roberto Violante3, Paula Franco-Fraguas4, Leticia Burone4, Cesar Barbedo Rocha5,a, Leonardo Ortega6, Rosangela Felicio dos Santos1, Bianca Sung Mi Kim1, Rubens Cesar Lopes Figueira1, and Marcia Caruso Bícego1 Michel Michaelovitch de Mahiques et al.
  • 1Oceanographic Institute of the University of São Paulo. 05508-120, São Paulo, Brazil
  • 2Institute of Energy and Environment of the University of São Paulo. 05508-010, São Paulo, Brazil
  • 3Servicio de Hidrografia Naval. C1270ABV, Buenos Aires, Argentina
  • 4Facultad de Ciencias, Universidad de La Republica. 11400, Montevideo, Uruguay
  • 5Woods Hole Oceanographic Institution. 02543-1050, Woods Hole, USA
  • 6Departamento de Biología Pesquera, Dirección Nacional de Recursos Acuáticos. 11200 Montevideo, Uruguay
  • apresently at: the Department of Marine Sciences, University of Connecticut. 06340, Groton, USA

Abstract. In this work, we provide an extensive inventory of Pb and Nd radiogenic isotopes in surface sediments from the Southwestern Atlantic margin, aiming to interpret the role played by ocean circulation in sediment distribution. There are latitudinal trends for Pb and Nd isotopes, reflecting the different current systems acting on the margin. The utilization of sediment fingerprinting allowed us to associate the isotopic signatures to the main oceanographic forcings in the area. We recognized differences between the Nd and Pb sources for the sediments to the Argentinean shelf, carried by the Subantarctic Shelf Water, and slope, transported by deeper flows. Sediments from Antarctica extend up to the Uruguayan margin, carried by the Upper- and Lower Circumpolar Deep Water. Our data confirm that, for shelf and intermediate (up to 1,200 m water depth) areas, the transfer of sediments from the Argentinean margin to the North of 35° S is limited by the Subtropical Shelf Front and the recirculated Antarctic Intermediate Water.

On the southern Brazilian margin, it is possible to recognize the northward influence of the Río de la Plata sediments carried by the Plata Plume Water. This influence is limited by the southward flow of waters transported by the Brazil Current. Finally, we propose that the Subtropical Shelf Front and the Santos Bifurcation act as boundaries of geochemical provinces in the area. Finally, a qualitative model of sediment sources and transport is provided for the Southwestern Atlantic margin.

Michel Michaelovitch de Mahiques et al.

Status: open (until 27 Jul 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on os-2021-44', Anonymous Referee #1, 18 Jun 2021 reply
    • AC1: 'Reply on RC1', Michel Mahiques, 22 Jun 2021 reply
  • RC2: 'Comment on os-2021-44', Anonymous Referee #2, 24 Jun 2021 reply

Michel Michaelovitch de Mahiques et al.

Michel Michaelovitch de Mahiques et al.


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Short summary
In this work we used a concept named Geochemical Fingerprinting, using isotopes of Neodymium and Lead as a tool to recognize the main sources and the phisical processes responsible for the transport and deposition of sediments on a large area of the South Atlantic margin. Distinct sources, such as Antarctica, the Andean Cordillera, the Río de la Plata basin, and the old rocks from the Brazilian shield are identified.