Mid- to late-Holocene paleoceanographic changes on the southeastern Brazilian shelf based on grain size records

Autor(es)

Gyllencreutz, R. ^[1] ; Mahiques, M. M. ^[2] ; Alves, D. V. P. ^[2] ; Wainer, I. K. C. ^[2]

Afiliação do(s) autor(es)

^[1] Univ Bergen, N-5020 Bergen - Norway

^[2] Univ Sao Paulo, BR-05508 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: HOLOCENE; v. 20, n. 6, p. 863-875, SEP 2010.
• Citações Web of Science: 43

Resumo

; High-resolution grain size analyses of three AMS (14)C-dated cores from the Southeastern Brazilian shelf provide a detailed record of mid- to late-Holocene environmental changes in the Southwestern Atlantic Margin. The cores exhibit millennial variability that we associate with the previously described southward shift of the Inter Tropical Convergence Zone (ITCZ) average latitudinal position over the South American continent during the Holocene climatic maximum. This generated changes in the wind-driven current system of the SW Atlantic margin and modified the grain size characteristics of the sediments deposited there. Centennial variations in the grain size are associated with a previously described late-Holocene enhancement of the El Nino-Southern Oscillation (ENSO) amplitude, which led to stronger NNE trade winds off eastern Brazil, favouring SW transport of sediments from the Paraiba do Sul River. This is recorded in a core from off Cabo Frio as a coarsening trend from 3000 cal. BP onwards. The ENSO enhancement also caused changes in precipitation and wind pattern in southern Brazil, allowing high discharge events and northward extensions of the low-saline water plume from Rio de la Plata. We propose that this resulted in a net increase in northward alongshore transport of fine sediments, seen as a prominent fine-shift at 2000 cal. BP in a core from similar to 24 degrees S on the Brazilian shelf. Wavelet-and spectral analysis of the sortable silt records show a significant similar to 1000-yr periodicity, which we attribute to solar forcing. If correct, this is one of the first indications of solar forcing of this timescale on the Southwestern Atlantic margin. (AU)

• Processo FAPESP: 03/10740-0 - Variações holocênicas na paleoprodutividade da Plataforma Continental Sudeste do Brasil
• Beneficiário: Michel Michaelovitch de Mahiques
• Modalidade de apoio: Auxílio à Pesquisa - Regular