Publicado por: inctambtropic | agosto 4, 2013

A Sedimentação na Plataforma Central do Brasil

Já encontra-se disponível “on line” o mais recente trabalho publicado no âmbito do inctAmbTropic. O trabalho intitulado “The narrow, shallow, low-accommodation shelf of central Brazil:  sedimentology, evolution, and human uses”   tem como autores Dominguez, JML, Silva, RP, Nunes, AS, Freire, AFM.  O trabalho está publicado na revista Geomorphology (Impact Factor: 2,552, 5-Year Impact Factor: 3,066).

Atividade Pesqueira na Borda da Plataforma Continental Central do Brasil

Atividade Pesqueira na Borda da Plataforma Continental Central do Brasil

O trabalho apresenta uma síntese e modelo conceitual da sedimentação na plataforma continental central do Brasil  e é  a primeira publicação a apresentar informações detalhadas para esta região.  O trabalho é uma contribuição do GT2.1 Geodiversidade e Biodiversidade dos Substratos do inctAmbTropic

ABSTRACT

The continental shelf off the coast of central Brazil, extending from 10 to 16°S, is unusually narrow (~ 20 km) and rests on the São Francisco craton. The shelf break is located between the 45 and 50 m isobaths and coincides with major hinge-lines of the marginal basins. The shelf was exposed for most of the Quaternary period, particularly during the last 1 my, when the average sea level was −62 m. Submarine geomorphology is strongly influenced by this extended sub-aerial exposure and reduced subsidence, resulting in widespread incisions on the shelf. During the limited episodes of shelf inundation, as is the case today, a few meters of non-framework grain assemblages dominated by coralline algae accumulated on the outer shelf, while quartz sands were restricted to water depths of less than 10–15 m. Mud accumulation on this unusually shallow shelf is aided by additional accommodation space provided by incisions and canyon heads indenting the shelf. Artisanal fisheries, targeting high-value commercial species associated with hard bottoms located on the outer shelf and shelf break, are the most important human use of this shelf. Data used in this study have been compiled from theses and previously conducted surveys and consist of four piston cores, 509 km of chirp subbottom profiles and side scan recordings, and 711 bottom grab samples that have been analyzed for various textural and compositional aspects.

Conceptual model for sedimentation in the narrow, shallow shelf off central Brazil.  Highstand sedimentation — during the few, brief highstand episodes, the shelf and coastal zone were flooded. Highstand coastal bays formed at the upstream end of incised valleys and were later infilled. On the shelf these incised valleys were partially infilled with fine-grained sediments. On the rest of the shelf, the reduced siliciclastic influx favored an essentially carbonate sedimentation, of non-framework rhodoalgal, oligophotic grain assemblages. Framework builders (hermatipic corals) developed on the very shallow areas bordering the coastline. Fonte: Dominguez, J.M.L., et al., The narrow, shallow, low-accommodation shelf of central Brazil: Sedimentology, evolution, and human uses, Geomorphology (2013), http://dx.doi.org/10.1016/j.geomorph.2013.07.004

Conceptual model for sedimentation in the narrow, shallow shelf off central Brazil. Highstand sedimentation — during the few, brief highstand episodes, the shelf and coastal zone were flooded. Highstand coastal bays formed at the upstream end of incised valleys and were later infilled. On the shelf these incised valleys were partially infilled with fine-grained sediments. On the rest of the shelf, the reduced siliciclastic influx favored an essentially carbonate sedimentation, of non-framework rhodoalgal, oligophotic grain assemblages. Framework builders (hermatipic corals) developed on the very shallow areas bordering the coastline. Fonte: Dominguez, J.M.L., et al., The narrow, shallow, low-accommodation shelf of central Brazil: Sedimentology, evolution, and human uses, Geomorphology (2013), http://dx.doi.org/10.1016/j.geomorph.2013.07.004

Chama-se a atenção que  a base de dados gerada para este trabalho está disponibilizada na forma de Dados Suplementares no portal do periódico Geomorphology, publicado pela Editora Elsevier, incluindo arquivos no formato kml para visualização da distribuição espacial do dados no Google Earth.


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