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(Referência obtida automaticamente do Web of Science, por meio da informação sobre o financiamento pela FAPESP e o número do processo correspondente, incluída na publicação pelos autores.)

Magnetic fingerprint of the late Holocene inception of the Rio de la Plata plume onto the southeast Brazilian shelf

Texto completo
Mathias, Grasiane L. [1] ; Nagai, Renata H. [2] ; Trindade, Ricardo I. F. [1] ; de Mahiques, Michel M. [2]
Número total de Autores: 4
Afiliação do(s) autor(es):
[1] Univ Sao Paulo, Dept Geofis, BR-05508090 Sao Paulo - Brazil
[2] Univ Sao Paulo, Inst Oceanog, BR-05508120 Sao Paulo - Brazil
Número total de Afiliações: 2
Tipo de documento: Artigo Científico
Citações Web of Science: 1

Measurement of changes in the assembly of magnetic particles in sediment records is useful both for paleoclimatic and paleoceanographic reconstructions and for assessing provenance and pathways of sediment transport In this study we provide detailed rock magnetic analysis along with scanning electron microscopy (SEM), Ti/Ca ratio and particle size distribution of the decarbonated fraction of sediments to trace terrigenous source changes during the last 6 cal kyr BP in core 7610 collected on the SE Brazilian continental shelf. Magnetic mineralogy data indicate a gradual shift between two distinct sources of sediments: (1) dust from southern South America (Patagonia, central western Argentina and Puna-Altiplano plateau) and (2) sediments eroded from the weathered volcanics of Parana Basin. These materials reached the continental margin off Argentina and Uruguay by different pathways and were transported northward by the Brazilian Coastal Current (BCC). The chronology of events related to the environmental record of core 7610 indicates that between 6 and 4.7 cal kyr BP dry conditions over continental South America resulted in enhanced eastward eolian transport of the Argentinean loess and a limited discharge of the RdlP river load into the Atlantic Ocean. At this time, the sedimentary magnetic fraction that reached the SE Brazilian shelf reflect predominantly loessic sources transported from the Pampean terraces to the Argentinean and Uruguay shelves and then distributed northward by the shelf current system. From 4.7 to 2 cal kyr BP the climate became gradually wetter over the continent and the contribution of oxidized phases from the weathered Parana Basin (mainly from the basaltic and acidic volcanics) started to become important This change in climate overlaps in time a with the late Holocene sea level fall recorded along the SE South American coast Later, from 2 up to 0.9 cal kyr BP even wetter conditions were prevalent in S and SE South America, and the RdlP sedimentary load became the main source of sediments transported to the SE Brazilian shelf by the BCC. The magnetic record of core 7610 reported here together with other paleoenvironmental tracers (palynology, geochemistry and stable isotopes) thus indicates that the inception of the RdlP plume onto the SE Brazilian shelf started as early as 4.7 cal kyr BP and has been strengthened since then mostly due to changes in precipitation over South America and to a smaller extent by sea-level changes. (C) 2014 Elsevier B.V. All rights reserved. (AU)

Processo FAPESP: 03/10740-0 - Variações holocênicas na paleoprodutividade da Plataforma Continental Sudeste do Brasil
Beneficiário:Michel Michaelovitch de Mahiques
Linha de fomento: Auxílio à Pesquisa - Regular
Processo FAPESP: 07/57124-2 - Intensidade relativa do campo magnético terrestre no Holoceno Pleistoceno a partir do estudo de sedimentos do pato de São Paulo
Beneficiário:Grasiane Luz Mathias
Linha de fomento: Bolsas no Brasil - Mestrado
Processo FAPESP: 09/01594-6 - Variações na produtividade da plataforma continental Sul-Sudeste do Brasil, no Holoceno Médio e tardio: uma abordagem "multiproxy"
Beneficiário:Renata Hanae Nagai
Linha de fomento: Bolsas no Brasil - Doutorado