Characterization of the Brazilian continental shelf adjacent to Rio Grande do Norte state, NE Brazil

This study focuses on the analysis of high-resolution seismic profiles, integrated with sedimentological, echosounder, SRTM and satellite image datasets, of the Brazilian continental shelf adjacent to the Rio Grande do Norte State, NE Brazil. Located in the northeast of Brazil, the State of Rio Grande do Norte is bounded by two main coastal and shelf systems: the eastern coastal-shelf, from the Sagi River to the Touros High, and the northern coastal-shelf, extending from Touros High to Tibau. This shelf represents a modern, highly dynamic mixed carbonate-siliciclastic system characterized by reduced width and shallow depths as compared with other parts of the Brazilian shelf. It has an average width of 40 km, the shelf-break lying at a depth of ~ 60 m. This shelf is subject to the full strength of the westerly South Equatorial current combined with high winds and moderate to high tides and waves. A sharply defined stratigraphic boundary, probably between the Pleistocene and Holocene deposits, is clearly to be observed in the seismic record. Incised-valleys extending from the main river mouths (e.g.the Potengi, Açu, and Apodi) to the shelf break dominate the area investigated and may indicate periods of lower sea level.Este estudo está direcionado ao conhecimento da plataforma continental brasileira adjacente ao Estado do Rio Grande do Norte, NE do Brasil, através da analise de perfis sismicos de alta resolução integrados a dados sedimentológicos, batimétricos, SRTM e imagens de satélites. O Estado do Rio Grande do Norte, localizado no nordeste do Brasil, apresenta dois sistemas costeiros-plataformais: Setor Este, do Rio Sagi (divisa PB-RN) ao Alto de Touros e Setor Norte, do Alto de Touros a Tibau (divisa RN-CE). Esta plataforma representa um sistema plataformal moderno misto (carbonático-siliciclástico), altamente dinâmico. É caracterizado por sua reduzida largura e águas rasas, quando comparado com outras partes da plataforma brasileira. A plataforma apresenta largura média de 40 km e a sua quebra encontra-se a profundidades médias de 60 m. A plataforma é sujeita a ação da corrente sul equatorial, combinada a ventos fortes e variação de maré moderada a alta e/ou ondas. Um limite estratigráfico fortemente definido, provavelmente entre os depósitos Pleistocênicos e Holocênicos, pode ser bem observado e vales incisos, estendendo-se a partir dos principais rios (como por ex., Potengi, Açu e Apodi) dominam a área investigada

Characterization of the Brazilian continental shelf adjacent to Rio Grande do Norte state, NE Brazil

This study focuses on the analysis of high-resolution seismic profiles, integrated with sedimentological, echosounder, SRTM and satellite image datasets, of the Brazilian continental shelf adjacent to the Rio Grande do Norte State, NE Brazil. Located in the northeast of Brazil, the State of Rio Grande do Norte is bounded by two main coastal and shelf systems: the eastern coastal-shelf, from the Sagi River to the Touros High, and the northern coastal-shelf, extending from Touros High to Tibau. This shelf represents a modern, highly dynamic mixed carbonate-siliciclastic system characterized by reduced width and shallow depths as compared with other parts of the Brazilian shelf. It has an average width of 40 km, the shelf-break lying at a depth of ~ 60 m. This shelf is subject to the full strength of the westerly South Equatorial current combined with high winds and moderate to high tides and waves. A sharply defined stratigraphic boundary, probably between the Pleistocene and Holocene deposits, is clearly to be observed in the seismic record. Incised-valleys extending from the main river mouths (e.g.the Potengi, Açu, and Apodi) to the shelf break dominate the area investigated and may indicate periods of lower sea level.Este estudo está direcionado ao conhecimento da plataforma continental brasileira adjacente ao Estado do Rio Grande do Norte, NE do Brasil, através da analise de perfis sismicos de alta resolução integrados a dados sedimentológicos, batimétricos, SRTM e imagens de satélites. O Estado do Rio Grande do Norte, localizado no nordeste do Brasil, apresenta dois sistemas costeiros-plataformais: Setor Este, do Rio Sagi (divisa PB-RN) ao Alto de Touros e Setor Norte, do Alto de Touros a Tibau (divisa RN-CE). Esta plataforma representa um sistema plataformal moderno misto (carbonático-siliciclástico), altamente dinâmico. É caracterizado por sua reduzida largura e águas rasas, quando comparado com outras partes da plataforma brasileira. A plataforma apresenta largura média de 40 km e a sua quebra encontra-se a profundidades médias de 60 m. A plataforma é sujeita a ação da corrente sul equatorial, combinada a ventos fortes e variação de maré moderada a alta e/ou ondas. Um limite estratigráfico fortemente definido, provavelmente entre os depósitos Pleistocênicos e Holocênicos, pode ser bem observado e vales incisos, estendendo-se a partir dos principais rios (como por ex., Potengi, Açu e Apodi) dominam a área investigada

Morfologia e sedimentologia da plataforma continental brasileira adjacente a São Bento do Norte e Caiçara do Norte-RN/NE-Brasil

This dissertation the results of a research developed in the area of São Bento do Norte and Caiçara do Norte, northern coast of the State of Rio Grande do Norte, during the period of June of 2000 to August of 2001, in the ambit of the projects MAMBMARÉ (CNPq/CTPETRO) and PROBRAL (CAPES/DAAD). The objective principal of this research was the characterization of the sedimentary dynamics of this coast, with base in data of coastal process (winds, currents, waves and tides), with topographical risings (beach profiles and dunes), satellite images and sedimentary analyses. The more specific objectives were accomplished the coastal monitoring of this coast, to verify the maintenance of an erosive tendency or progradacional after the groynes construction for contention of the erosion in the beach of Caiçara do Norte, as well as to verify the influence of the features of bottom of the platform interns adjacent on the pole petroliferous of Guamaré. The executed monitoramento allowed to identify that the movement of the sediments, along the year, in that area, is cyclical, reaching the largest oscillations during the months of winter (deposition) and they will summer (erosion). The sedimentologic studies indicated a general tendency for sands quartzosas, with gravel presence, moderately to good selected, with asymmetry predominantly negative. In agreement with the parameter of Dean (1957), used in the identification of the state morfodinâmico of the beaches, monitored beaches, are basically reflectivas with tendency to middlemen, what frames that space of the coast norte-riograndense, as a space strongly vulnerable to erosive processes. The studies developed in the platform, it interns of this area, allowed to visualize for the first time, in large scale, the distribution of the features of the submarine bottom to the batométrico coat of 25 meters. Being pointed out the presence of a high one topographical submerged, with about 5 meters of height, 1 km of width and more than 24 meters of extension, located in the platform it interns in front of São Bento do Norte; coincident with the trend of the system of flaws of Carnaubais. This feature relay an important paper on the control of the sedimentary processes and oceanographic, as well as in the coastal evolution of this area of the RN state, and they affect the area of the pole petroliferous of Guamaré directly. These results contribute to a better knowledge of the processes in the area, and consequently as subsidies implantation of measures of coastal and environmental protection for the cities of São Bento do Norte and Caiçara do Norte, as well as to understand how the geological-sedimentary processes and oceanographic, in this area, are influencing the characteristics geoambientais of the pole petroliferous of GuamaréEsta dissertação apresenta os resultados de uma pesquisa desenvolvida na região de São Bento do Norte e Caiçara do Norte, litoral setentrional do Estado do Rio Grande do Norte, durante o período de Junho de 2000 a Agosto de 2001, no âmbito dos projetos MAMBMARÉ (CNPq/CTPETRO) e PROBRAL (CAPES/DAAD). O objetivo principal da pesquisa foi a caracterização da dinâmica sedimentar do litoral em questão, com base em dados relativos à dinâmica costeira (ventos, correntes, ondas e marés), levantamentos topográficos (perfis de praia e dunas), imagens de satélite e análises sedimentológicas. Como objetivos específicos foram realizados o monitoramento deste litoral, com o fim de verificar a manutenção de uma tendência erosiva ou progradacional após a construção de gabiões para contenção da erosão na praia de Caiçara do Norte, bem como verificar a influência das feições de fundo da plataforma interna adjacente sobre o pólo petrolífero de Guamaré. O monitoramento executado permitiu identificar que a movimentação dos sedimentos, ao longo do ano, nessa região, exibe um padrão cíclico, atingindo as maiores oscilações durante os meses de inverno (deposição) e verão (erosão). Os estudos sedimentológicos indicaram uma tendência geral para areias quartzosas, com presença de cascalho, moderadamente a bem selecionadas, com assimetria predominantemente negativa. De acordo com o parâmetro de Dean (1957), as praias monitoradas são basicamente reflectivas com tendência a intermediárias, o que enquadra esse trecho da costa norte-riograndense como fortemente vulnerável a processos erosivos. Os estudos desenvolvidos na plataforma interna desta região permitiram visualizar pela primeira vez, em macroescala, a distribuição das feições do fundo submarino até a isóbata de 25 metros. Ressaltando-se a presença de um alto topográfico submerso, com cerca de 5 metros de altura, 1 km de largura e mais de 24 metros de extensão, localizado na plataforma interna em frente a cidade de São Bento do Norte, coincidente com o trend do Sistema de Falhas de Carnaubais. Esta feição exerce um papel importante no controle dos processos sedimentares e oceanográficos, bem como na evolução costeira desta região do Estado do RN, que afetam diretamente a região do pólo petrolífero de Guamaré. Estes resultados contribuem para um melhor conhecimento dos processos atuantes na região e, conseqüentemente, fornece subsídios para a implementação de medidas de proteção costeira e ambiental para as cidades de São Bento do Norte e Caiçara do Norte, bem como para o melhor entendimento de modo como os processos geológicos e oceanográficos atuantes nesta área, vêm influenciando nas características geoambientais do pólo petrolífero de Guamar

Bedforms patterns characterization of the São Francisco River

On the basis of a regional side-scan sonar survey covering a distance of 12 km on the São Francisco River Mouth between Piaçabuçu and Cabeço-Pontal da Barra (NE Brazil) a variety of bedforms have been distinguished. The river bed morphology of this area can be characterized by three main patterns: dunes, ripples and planar beds. Sand dunes occur as extensive 2D and 3D dune fields. Between Piaçabuçu and Fitinha Island the dunes are asymmetric indicating a sand movement toward the river mouth. These dunes range in height from 1 to 2 m, and in wavelength from 30 to 90 m. Between Fitinha Island and Negra Island large asymmetric dunes with smaller symmetric ones superimposed can be seen, showing tidal influence. At the river mouth, the dunes give place to symmetrical ripples with height smaller than 0,3 m and wavelength shorter than 1 m. The dune and ripples fields can be intercalated by planar beds

Control of the coastal setting in the São Bento do Norte and Caiçara do Norte Beach - NE/Brasil

Sedimentary dynamic studies were conducted on the North littoral of Rio Grande do Norte State, comprising the São Bento do Norte and Caiçara do Norte cities, based on coastal processes data (wind, currents, waves and tides), beach profiles (monitoring six beach profiles, between June of 2000 and august of 2001), and elements in the morphologic and structural features. The coastline changes due to erosion and deposition are the major concern for the coastal zone management of this area. This work is setting the necessity to understand the causes of erosion before construction of protective structure on erosional beaches. Some items can be observed: 1) The destruction effects in the coastline were not eliminated by the construction of a groyne-field; 2) The increase of the erosion process in the area after the last groyn. The main modifications happened on the months of November 2000 and March 2001, probably conditioned mainly by the change of the medium direction of the winds, that varied from 225ºAz to 320ºAz in this period of 14 months of monitoring. In the month of November 2000, the registered average was of the order of 72ºAz (profile P1) and 90ºAz (profile P6), in the same sequence we obtained a variation of the order of 95ºAz and 85ºAz, for the month of March of 2001. In this context, it was observed that the period of repetition of the waves reached averages of the order of 2’03”Seg (mar/01, profile P1) and 6’07”Seg (mar/01, profile P6). The height of the waves was also registered in this period as being the highest, with values of 0,44m (mar/01, profile P1) and 0,50m (mar/01, profile P6). The beaches in the studied area can be classified as reflective to intermediate