Sedimentation in the adjacencies of a southwestern Atlantic giant carbonate ridge

Autor(es)

Rosangela Felicio dos Santos ^[1] ; Bianca Sung Mi Kim ^[2] ; Tailisi Hoppe Trevizani ^[3] ; Rodrigo Udenal de Oliveira ^[4] ; Mascimiliano Maly ^[5] ; Raissa Basti Ramos ^[6] ; Rubens Cesar Lopes Figueira ^[7] ; Michel Michaelovitch de Mahiques

Afiliação do(s) autor(es)

^[1] Universidade de São Paulo. Instituto Oceanográfico - Brasil

^[2] Universidade de São Paulo. Instituto Oceanográfico - Brasil

^[3] Universidade de São Paulo. Instituto Oceanográfico - Brasil

^[4] Universidade de São Paulo. Instituto Oceanográfico - Brasil

^[5] Universidade de São Paulo. Instituto Oceanográfico - Brasil

^[6] Universidade de São Paulo. Instituto Oceanográfico - Brasil

^[7] Universidade de São Paulo. Instituto Oceanográfico - Brasil

• Tipo de documento: Artigo Científico
• Fonte: Ocean and Coastal Research; v. 70, 2022-10-03.

Resumo

Abstract Although carbonate mounds have been investigated for 100 years, few studies focus on the giant variety. The Alpha Crucis Carbonate Ridge (ACCR), a ~17 x 12-km ring-shaped ridge formed by hundreds of mounded structures, located between the 300 and 800-m isobaths and reaching a maximum height of 340 meters above the adjacent seafloor, is the first giant carbonate mounded feature described for the SW Atlantic margin. This study provides the first multiproxy approach to investigate sediments covering the ACCR and its adjacencies. Most of the area is located under the Intermediate Western Boundary Current (IWBC) flow, which carries the nutrient-rich Antarctic Intermediate Water (AAIW). Radiocarbon aging shows pronounced differences for the shallow layers (MIS3 for the top of the mounds and late Holocene for the adjacencies). Grain size data indicate the prevalence of sandy fractions on top of the mounds and muddy sediments in the adjacent areas. Fe/Ca and Ti/Ca proxies allowed for identifying mainly biogenic sedimentation in the area. However, the input of allochthonous terrigenous sediment is necessary for mound buildup, and values of Fe and Ti collected on the top of the mounds are significant. End-Members distributions and metal concentrations also allowed for recognition of distinct sources of sediment. εNd and Ln(Fe/K) indicated two primary terrigenous sources, the Precambrian rocks of the Brazilian shield (Cabo Frio end-member) and the multiple lithologies drained by the Rio de la Plata basin. Redox condition proxies indicated that the area is submitted to oxic conditions, probably reflecting the action of the IWBC. This work provides the first insight into an integrated grain-size and geochemical characterization of the Alpha Crucis Carbonate Ridge (southwestern Atlantic margin). (AU)

• Processo FAPESP: 14/08266-2 - Feições morfológicas do talude continental da margem Sudeste do Brasil: tectônica ativa versus condições oceanográficas modernas
• Beneficiário: Michel Michaelovitch de Mahiques
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 10/06147-5 - Incremento da capacidade de pesquisa em oceanografia no estado de São Paulo
• Beneficiário: Michel Michaelovitch de Mahiques
• Modalidade de apoio: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Regular