Banca de QUALIFICAÇÃO: LUZIA LINIANE DO NASCIMENTO SILVA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
DISCENTE : LUZIA LINIANE DO NASCIMENTO SILVA
DATA : 15/06/2016
HORA: 14:00
LOCAL: Sala 01 PPGG
TÍTULO:

Geomorphology and Sedimentology of the outer contiental shelf in the northeastern of Rio Grande do Norte

PALAVRAS-CHAVES:

reefs, sediments, geomorphology, backscatter, continental shelf

PÁGINAS: 20
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Geociências
RESUMO:

The northern outer continental shelf of Rio Grande do Norte is a transition zone of physiography, for sedimentological, physical and biological oceanographic processes, and was marked by eustatic variations. The sedimentary evolution of these transition areas can be revealed by geomorphological and sedimentological data. Thus, the sonographic method and sedimentological sampling techniques were employed. The side scan sonar was used to map an area parallel to the shelf break, with about 413 Km2, in three subareas of study. We identified 12 backscattering patterns (P1 to P12) associated with 12 sedimentary facies (bioclastic to siliciclastic), reef fields that extend for over 30 km parallel to the shelf break, and the paleovalley of the Acu River crossing the outer shelf and separating the area 3 from the others. The analysis of statistical parameters: degree of selection, skewness and kurtosis revealed a poorly selecionamento sediment. The facies bioclastic sands with gravel is predominant, related to the backscatter pattern P4. The bioclastic sands with gravel are the main facies responsible for the high percentage of organic matter and carbonate content. The sedimentary facies of outer shelf demonstrate the relationship between the distribution of existing sediments and reefs. The finer sediments are concentrated in the valley and among the reefs. Greater heterogeneity of facies occurs in regions with no geomorphological protection. The richest area in carbonate content is close to the valley and the reefs of the area 2 study, however, the region that concentrates reefs is one area of lowest level of organic matter. The reefs were classified as mounds and are elongated in the NW-SE direction and they extend for several kilometers. They are located between 20 - 50 m water depth, the average values of 5 m in height, 135 m in length for elongated reefs and 26 m for the diameter concentric forms. The alignment of the reefs can be  evidence antecedent substrates that may represent features subject to the effect of waves and tides, as ancient shorelines. The valley of Açu may have conditioned the development of reefs in periods of rising sea level. The distribution of sedimentary facies and the statistical parameters suggest that the sedimentation of the outer shelf was set up under a variable hydrodynamic energy. In addition, the reef field serves to trap easterly sediments migrating and making distinct sedimentation processes inside and outside the reef field. Thus, the pattern in areas below 50 m and above 20 m depth is locally independent, producing a sedimentations zonation of outer shelf. Therefore, the geomorphology has a fundamental role in modern sedimentation of the Outer Continental Shelf.

MEMBROS DA BANCA:
Interno - 2218779 - HELENICE VITAL
Externo à Instituição - LEAO XAVIER DA COSTA NETO - IFRN
Presidente - 2042405 - MOAB PRAXEDES GOMES