Sedimentary particle distribution and dynamics on the Nazaré canyon system and adjacent shelf (Portugal)

In the framework of the EUROSTRATAFORM project 108 bottom sediment samples (1st cm) from the Nazaré continental shelf have been analysed for grain-size, mineralogy (X-ray diffraction) organic carbon and carbonate contents. The particulate matter (PM) from intermediate (INL) and bottom nepheloid laye...

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Bibliographic Details
Published in:Marine geology 2007-12, Vol.246 (2), p.105-122
Main Authors: Oliveira, A., Santos, A.I., Rodrigues, A., Vitorino, J.
Format: Article
Language:English
Subjects:
canyon
fine sediments
Iberian margin
mineralogy
Nazaré
source areas
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Summary:In the framework of the EUROSTRATAFORM project 108 bottom sediment samples (1st cm) from the Nazaré continental shelf have been analysed for grain-size, mineralogy (X-ray diffraction) organic carbon and carbonate contents. The particulate matter (PM) from intermediate (INL) and bottom nepheloid layers (BNL) was also analysed in 84 stations for grain-size and composition. The particle analysis was related to the present day sedimentary processes directly promoted (or intensified) by the presence of the Nazaré submarine canyon. The Nazaré canyon intersects the entire continental shelf and may act as a catchment area for material which is transported over the shelf, but its complex dynamics will extend to sediment distribution on the adjacent shelf. Major areas of erosion and resuspension and calmer areas where fine muddy sediments can settle on a temporary or permanent timescale were identified by their mineralogical and organic carbon (C org) distribution pattern. According to this data the Victoria tributary and the Nazaré canyon head (280–300 m) seem to act as permanent depocenters. A conceptual model was proposed to delineate the mechanisms acting in this particular area, taking into account three different sources of material to the Nazaré canyon: 1. during upwelling conditions, resuspension of middle shelf deposits by internal wave activity and transport to the canyon in the BNL; 2.erosion of northern/southern beach and sea cliff materials transported by littoral drift to the canyon head and 3. fine sediment input from the southern river and transport to the canyon, during downwelling conditions (winter).
ISSN:0025-3227
1872-6151
DOI:10.1016/j.margeo.2007.04.017