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Depositional provinces, dispersal, and origin of terrigenous sediments along the SE South American continental margin

Texto completo
Autor(es):
Razik, Sebastian [1] ; Govin, Aline [2] ; Chiessi, Cristiano M. [3] ; von Dobeneck, Tilo [2, 1]
Número total de Autores: 4
Afiliação do(s) autor(es):
[1] Univ Bremen, Dept Geosci, D-28359 Bremen - Germany
[2] Univ Bremen, MARUM Ctr Marine Environm Sci, D-28359 Bremen - Germany
[3] Univ Sao Paulo, Escola Artes Ciencias & Humanidades, BR-03828000 Sao Paulo, SP - Brazil
Número total de Afiliações: 3
Tipo de documento: Artigo Científico
Fonte: MARINE GEOLOGY; v. 363, p. 261-272, MAY 1 2015.
Citações Web of Science: 5
Resumo

Continental margin sediments of SE South America originate from various terrestrial sources, each conveying specific magnetic and element signatures. Here, we aim to identify the sources and transport characteristics of shelf and slope sediments deposited between East Brazil and Patagonia (20 degrees-48 degrees S) using enviromagnetic, major element, and grain-size data. A set of five source-indicative parameters (i.e., chi(fd)%, ARM/IRM, S-0.3T, SIRM/Fe and Fe/K) of 25 surface samples (16-1805 m water depth) was analyzed by fuzzy c-means clustering and non-linear mapping to depict and unmix sediment-province characteristics. This multivariate approach yields three regionally coherent sediment provinces with petrologically and climatically distinct source regions. The southernmost province is entirely restricted to the slope off the Argentinean Pampas and has been identified as relict Andean-sourced sands with coarse unaltered magnetite. The direct transport to the slope was enabled by Rio Colorado and Rio Negro meltwaters during glacial and deglacial phases of low sea level. The adjacent shelf province consists of coastal loessoidal sands (highest hematite and goethite proportions) delivered from the Argentinean Pampas by wave erosion and westerly winds. The northernmost province includes the Plata mudbelt and Rio Grande Cone. It contains tropically weathered clayey silts from the La Plata Drainage Basin with pronounced proportions of fine magnetite, which were distributed up to similar to 24 degrees S by the Brazilian Coastal Current and admixed to coarser relict sediments of Pampean loessoidal origin. Grain-size analyses of all samples showed that sediment fractionation during transport and deposition had little impact on magnetic and element source characteristics. This study corroborates the high potential of the chosen approach to access sediment origin in regions with contrasting sediment sources, complex transport dynamics, and large grain-size variability. (C) 2015 Elsevier B.V. All rights reserved. (AU)

Processo FAPESP: 12/17517-3 - Resposta da porção oeste do Oceano Atlântico às mudanças na circulação meridional do Atlântico: variabilidade milenar a sazonal
Beneficiário:Cristiano Mazur Chiessi
Linha de fomento: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Jovens Pesquisadores