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Título

Record of larger benthic foraminifera from the Rio Grande Rise: chronostratigraphic and paleoenvironmental insights

Texto do resumo

The Rio Grande Rise is an oceanic plateau located in the southeastern Atlantic Ocean, whose formation dates back to the Late Cretaceous, originating from a mantle plume followed by events of magmatic reactivation and subsidence. These processes resulted in uplift accompanied by volcanism, culminating in a subaerial exposure at the end of the Paleogene, and subsequent erosion to its current morphology. In our study, samples of the carbonate oceanic substrate of the rise, collected through dredging by the Serviço Geológico do Brasil (SGB), were analyzed. The objective of this work is to corroborate and better understand this emerged phase of the rise through the fossil record of large benthic foraminifera. These unicellular organisms, characterized by calcareous shells, play a crucial role as paleoenvironmental indicators and biostratigraphic tools, reflecting influences of environmental factors such as water temperature, salinity, nutrients, and depth. The analyzed samples taxonomically identified the presence of species and/or genera such as Lepidocyclina sp., Lepidocyclina canellei, Lepidocyclina (Nephrolepidina) ferreoi, and Katacycloclypeus martini, associated with red algae grainstones, packstones and bindstones. The presence of these species in our material suggests an age ranging from the Oligocene to the Miocene, indicating a shallow reef environment. This depositional features are consistent with the geological evolution of the Rio Grande Rise, comprising a submerged shallow carbonate platform associated with a volcanic island in the Southwest Atlantic Ocean. These findings unveil important aspects of the evolutionary history and past environmental conditions of the ancient Rio Grande Rise.

Palavras Chave

Larger Benthic Foraminifera; Rio Grande Rise; Southwest Atlantic; Shallow water carbonates