Sedimentation in the adjacencies of a southwestern Atlantic giant carbonate ridge

Author(s)

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

Affiliation

^[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

• Document type: Journal article
• Source: Ocean and Coastal Research; v. 70, 2022-10-03.

Abstract

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)

• FAPESP's process: 14/08266-2 - Continental slope morphological features on the SE Brazilian Margin: active tectonics versus modern oceanographic conditions
• Grantee: Michel Michaelovitch de Mahiques
• Support Opportunities: Regular Research Grants
• FAPESP's process: 10/06147-5 - Increase of the research capabilities in oceanography and related sciences in São Paulo State, Brazil
• Grantee: Michel Michaelovitch de Mahiques
• Support Opportunities: Research Program on Global Climate Change - Regular Grants