Morfologia e sedimentação da Plataforma do Atol das Rocas
The Rocas Atoll is in the Fernando de Noronha Fracture Zone, South Atlantic Ocean, developed on top of an ancient oceanic volcano mainly during the Holocene. Quaternary sea level fluctuations left geomorphic marks on the atoll and its surrounding shelf. This study investigated the geomorphology and...
Na minha lista:
| Autor principal: | |
|---|---|
| Outros Autores: | |
| Formato: | Dissertação |
| Idioma: | pt_BR |
| Publicado em: |
Universidade Federal do Rio Grande do Norte
|
| Assuntos: | |
| Endereço do item: | https://repositorio.ufrn.br/handle/123456789/45608 |
| Tags: |
Adicionar Tag
Sem tags, seja o primeiro a adicionar uma tag!
|
| Resumo: | The Rocas Atoll is in the Fernando de Noronha Fracture Zone, South Atlantic Ocean,
developed on top of an ancient oceanic volcano mainly during the Holocene. Quaternary
sea level fluctuations left geomorphic marks on the atoll and its surrounding shelf. This
study investigated the geomorphology and sedimentation of Rocas Atoll shelf based on
single-beam, sonography, grabbed bottom sediments, and multi-temporal satellite
imagery. The Rocas Atoll has a surrounding shelf with general E-W orientation, mostly
flat with water depth of 25 m. The shelf break occurs between 45 and 50 m water depth,
reaching up to 80 m locally on northwestern. The shelf is compartmentalized into inner
and outer zones that are limited by step-terraces features. The first terrace level (T1)
occurs at ~70 m depth, the second terrace (T2) at 40 m depth and the third terrace level
(T3) occurs at 30 m depth. Most of the hard-bottoms are reefs. Close to the atoll, in
shallow depths, reefs occur aggregated, forming a tridimensional structure of low relief
mounds and paths. As the water depth increases towards the outer shelf, the reefs occur
isolated. ENE-WSW longitudinal and WNW-ESE transversal dunes migrate along the
shelf. The geomorphologic patterns of this shelf are analogous to the northeast Brazilian
shelf, reflecting the influence of Pleistocene/Holocene sea-level oscillations.
Furthermore, the modern processes of reef erosion, as a response to decadal climate
phenomena as El Niño, intensify the shelf sedimentation and the South Equatorial
Currents shape the modern shelf and affect seasonally the sediment transport and sand body dimensions. |
|---|