Abstract
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.
Highlights
Research on the Brazilian tropical shelf had its roots in the 1960s and 1970s (e.g. ZEMBRUSCKI, 1967; COUTINHO; MORAES, 1968; MABESOONE; COUTINHO, 1970; MILLIMAN et al, 1975; SUMMERHAYES et al, 1975)
The study area, the Rio Grande do Norte (RN) tropical northeast shelf, represents a modern, highly dynamic mixed carbonate-siliciclastic shelf system and comprises two different sectors separated by the Touros structural high 1) an eastern sector extending from the Sagi River to the Touros High and 2) a northern sector extending from the Touros high to Tibau City (Fig. 2)
The continental shelf edge runs parallel to sub-parallel to the coast with a very sharp shelf break that starts at a depth of about 70 - 80 m around the Touros High and decreases westwards to 40-50 m depth, and southwards to 50-60 m (Fig. 3)
Summary
Research on the Brazilian tropical shelf had its roots in the 1960s and 1970s (e.g. ZEMBRUSCKI, 1967; COUTINHO; MORAES, 1968; MABESOONE; COUTINHO, 1970; MILLIMAN et al, 1975; SUMMERHAYES et al, 1975). In the same line of research, new seismic and sedimentological data were incorporated by the LEPLAC project (Brazilian Continental Shelf Survey) from 1987 to 1996 and most recently, the REMPLAC (Mineral Reconnaissance of the Brazilian Continental Margin) initiative which began in 1997. Bilateral cooperation, such as the Brazilian/German Joint Oceanographic Projects (JOPS) that were begun in the 1990s, have contributed to knowledge of the tropical Brazilian shelf The recognition of the complexity of oceanographic processes in coastal environments near large rivers and of the interrelationship of the processes involved, led to the interdisciplinary approach of AmasSeds (A Multidisciplinary Amazon Shelf Sediment Study) from 1980 to 1996, which was coordinated by academic institutions in the USA and Brazil. The results of these studies have been published for specific fields of oceanography (e.g. BEARDSLEY et al, 1995; GEYER; KINEKY, 1995; NITTROUER et al, 1996; NITTROUER ; DEMASTER, 1996) making the northern Brazilian shelf one of the most studied maritime areas in Brazil
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