Sedimentos superficiais da plataforma continental interna do estado da ParaÃba

AUTOR(ES)
DATA DE PUBLICAÇÃO

1999

RESUMO

The internal continental shelf in the state of ParaÃba was divided into three sectors: central and northern, considering the coastal line morphology, bathymetric features and sedimentary information. The southern sector comprises the region extending the latitude 7Â35â00âS to Branco Cape. The coastal line is basically staight, trending N-S, characterized by a narrow sandy coastal plain. The Barreiras Formation sediments at the coastal line form active cliffs. Cut by small estuaries. The sediments includes gravel (3%), sand (82%) and mud (15%), in wnich predominates clastic sediments (61%). The central sector includes the region fron Branco Cape to Mamanguape River. The coastal line trends N20W, being the most cut. This sector show a more developed coastal plain, due to the absence of Barreiras Formation sediments. The sediments are composed of gravel (4%), sand (68%) and mud (28%), in wich carbonatic sediments dominantes (66%). The northern sector goes fron the Mamanguape River to the latitude 6Â35â00â. Its coastal is straight, trending N-S, cut by small estuaries and the TraiÃÃo Bay. This sector is characterized by coastal plain less developed than the previous one, however, it does not have Barreiras Formation sediments at the coastal line. The sediments are characterized by gravel (15%), sand (74%) and mud (11%), in which the clastic componente predominates (76%). In the three sectors the isobaths show morphological irregularities with narrow and inclined regions compared to others wider and less inclined. These irregularities are a consequence of depositional processes variations and sea level relative fluctuations, resulting in erosion and deposition, forming erosive and constructive features. One of the most characteristic morphological feature in this platform is the presence of sand, coral and calcareous algae reefs. They influence the coastal line morphology, the hydrodymamic processes, the facies distribuition, being the main source of organic sediments. The facies were defined, according to their calcium carbonate content and texture, in: lithoclastic gravel, bioclastic gravel, lithoclastic sand, bioclastic sand, lithoclastic mud, bioclastic mud and reefs. Five provinces were defined according to the sedimentary zonation: active littoral lithoclastic province, active bioclastic province, transitional lithoclastic/bioclastic province, relict lithoclastic province and relict bioclastic province. The sediments show evidence of textural equilibrium, however some are in desequilibrium with present day conditions. The semi-arid conditions in the ParaÃba state coastal determine na inexpressive and intermittent drainege network, wich causes a low terrigenous sedimentation rate. The physical weathering contributs to a low suspended matter in the river water

ASSUNTO(S)

plataforma continental interna easy desimentares bioclÃsticos fÃcies sedimentares provÃncias sedimentares bioclÃsticos batimÃtria litoclÃsticos sedimentary provinces continental platform interns batimÃtria geociencias litoclÃsticos

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