Morfodinâmica de formas de fundo em águas rasas na Plataforma Tropical Setentrional do Rio Grande do Norte
Bedforms are important morphological elements of shallow marine environments, working as major contributors to the sediment flow on the shelf. This research proposes to analyze the shallow-water bedforms morphodynamic on the continental shelf adjacent to Galinhos – Guamaré (RN). We integrated sin...
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| Natura: | Dissertação |
| Lingua: | por |
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| Accesso online: | https://repositorio.ufrn.br/jspui/handle/123456789/26273 |
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| Riassunto: | Bedforms are important morphological elements of shallow marine environments,
working as major contributors to the sediment flow on the shelf. This research
proposes to analyze the shallow-water bedforms morphodynamic on the
continental shelf adjacent to Galinhos – Guamaré (RN). We integrated singlebeam
bathymetry, Landsat 8 OLI image, swath bathymetry and sonography,
scuba diving video and sediment samples. Two data acquisition campaigns were
realized with a difference of two years. The sand ridges field (SRF) is visible by
satellite image. SRF is limited between 5 to 10 m depth, stretched to E-W. This
field is composed by sand ridges parallel to the coastline in the west and oblique
when near the coastline. The SRF is shaped by the dunes amalgamation with
crest to SW-NE direction. The dunes have 1 to 4 meters, with 400 to 1200 meters
wavelength. The sand ridge coastline flank is straighter, on the other hand the
offshore side has reentrances. On the coast, from east to west, there is the spit
of Galinhos, the ebb tidal delta of Guamaré, the Canto do Amaro barrier island
system and the Minhoto beach. From the mosaic generated by the sonar data,
ripples were described, with SE-NW crests, superimposing the dunes. Scuba
diving videos show symmetrical ripples, sometimes with red algae (rhodolites) in
the trough. Four backscatter patterns were identified. This pattern is related to
the four sedimentary facies founded. The integration of remote sensing, current
and sedimentological data of distinct periods allowed to identify the
morphodynamic of the bedforms and sedimentary cover in the shallow water. The
coastal drift and the ebb-tidal delta of Guamaré influenced the actual SRF shape.
SR dunes asymmetry shows that NW current formed these dunes. But actually
they are inactive. Ripples have SW drift. This movement of sediments between
the dunes occurs in the troughs. These ripples probably have the dynamics
difficult by the presence of red algae in seabed. SRF origins might be related to
Holocene sea-level rise and ebb-tidal deltas. |
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