Distribuição dos foraminíferos bentônicos recentes e sua relação com os parâmetros sedimentológicos e oceanográficos da bacia do Espírito Santo

• Ano de defesa: 2022
• Autor(a) principal: Almeida, Fabiana Karla de
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal do Espírito Santo; BR; Doutorado em Oceanografia Ambiental; Centro de Ciências Humanas e Naturais; UFES; Programa de Pós-Graduação em Oceanografia Ambiental
• Palavras-chave em Português: Foraminíferos Bentônicos; Mar Profundo; Fluxo de Matéria Orgânica; Talude; Margem Continental Brasileira; subject.br-rjbn; Ciências Ambientais
• Link de acesso: http://repositorio.ufes.br/handle/10/16588

The heterogeneity of the seafloor at the Brazilian Continental Margin may result in differences in the benthic foraminiferal assemblages composition. To understand the main environmental factors controlling the benthic foraminiferal distribution on the continental slopes, and corroborate paleoenvironmental interpretations in the Late Holocene, the benthic foraminiferal assemblages (total fauna > 63 µm) and sedimentological data were investigated along six transects on the continental slope, and within two submarine canyons of the Espírito Santo Basin (ESB, 18°20' and 21°20' S). Surface sediment samples (0-2 cm) were collected perpendicularly to the coast, from the upper (400 m) to the lower slope (3000 m). Inside the Watu Norte (CANWN) and Doce (CAND) canyons, samples were collected from the canyon head to the middle-lower canyon (150 to 1300 m). The density, taxonomic diversity, and assemblage composition change with depth and between the canyons. The differences in ecological preferences among the most abundant taxa allowed the recognition of distinct benthic foraminiferal groups, distributed in five main bathymetric sectors: outer shelf (50m), upper (150-400 m), middle – lower (1000-1300 m), lower slope (1900 m), and deepest lower slope (2500- 3000 m). In addition, two different groups were recognized, revealing differences between individual submarine canyons assemblages. The quantity and quality of food supply is the primary factor controlling the distribution of benthic foraminiferal assemblages along depth. Secondary factors include the properties of water masses, intermediate and deep boundary currents, sediment type and grain size. The increased fragmentation of benthic and planktic foraminifera tests (>125 µm) is related to abrasion during transport from shallower regions to the slope. The middle-lower CANNW indicated unstable trophic conditions, related to terrigenous sediment influx due to turbidity currents. In the CAND, foraminiferal assemblages ecology indicated enough organic matter content that benefits species establishment and diversity, revealing an environment more productive and less unstable than the CANWN. The data obtained in this study could be used as analogues in the interpretation of older marine depositional systems, helping to generate more accurate paleoenvironmental and paleobathymetric models of the Espírito Santo Basin.