Banca de DEFESA: FRANCISCO CORDEIRO DO NASCIMENTO NETO

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : FRANCISCO CORDEIRO DO NASCIMENTO NETO
DATA : 24/08/2018
HORA: 10:00
LOCAL: Sala 1 - PPGG
TÍTULO:

Shallow-water bedforms morphodynamic at a tropical shelf – Northeast of Brazil: a multiscale approach

PALAVRAS-CHAVES:

Bedform; morphodynamics; subaqueous dunes; ripples

PÁGINAS: 110
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Geociências
RESUMO:

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. We integrated single-beam 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 subaqueous dunes field (SDF) is visible by satellite image. SDF 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 to the coast in the eastern part of the field. The SDF 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, measured from the single-beam bathymetry. The sand ridge flank facing coastline is straighter, on the other hand the side facing offshore has reentrances. On the coast, from east to west, there is the spit of Galinhos, the ebb tidal delta of the Guamaré tidal inlet, the Canto do Amaro barrier island system and the beach of Minhoto. 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 found and change with the carbonate bulk content. The area is sandy covered, with variations of 10% to 80% carbonate. The integration of remote sensing, current and sedimentological data of distinct periods allowed to identify the morphodynamics of the bedforms and sedimentary cover in the shallow water. The coastal drift and the tide inlet of Guamaré influenced the current shape of the SDF. The difference in the data of bathymetry suggests a drift of the dunes to NW, also showing by its asymmetry. Ripples have SW drift; however, ripples superimposed the ridges of the dunes is drifting to NW. The passage of sediments between the dunes occurs through the trough. These ripples probably have the dynamics difficult by the presence of red algae in the trough.

MEMBROS DA BANCA:
Externo à Instituição - ELÍRIO ERNESTINO TOLDO JUNIOR - UFRGS
Presidente - 2218779 - HELENICE VITAL
Externo ao Programa - 2177287 - ZULEIDE MARIA CARVALHO LIMA