Sediment partitioning and winnowing in a mixed eolian-marine system (Mauritanian shelf) |
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Authors: | Julien Michel Hildegard Westphal Till J J Hanebuth |
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Institution: | (1) MARUM—Center for Marine Environmental Sciences, University of Bremen, Leobener Strasse, 28359 Bremen, Germany;(2) MARUM—Center for Marine Environmental Sciences, and Department of Sedimentology/Palaeoceanography, Faculty of Geosciences, University of Bremen, Klagenfurter Strasse, 28359 Bremen, Germany |
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Abstract: | Continental shelf systems are highly dynamic sedimentary environments, where sediments from biogenic production as well as
from terrigenous sources are redistributed in the shelf depositional system, and partly exported off the shelf to the slope
and the deep sea. The Golfe d’Arguin (Mauritania, NW Africa) is dominated by such redistribution processes, involving clastic
silt imported as dust from the Sahara desert and biogenic carbonates of marine origin. Indeed, surface-sediment grain size
and mineralogy show a clear north–south partitioning of sediment type. Fine material is winnowed from the northern part of
the gulf, and transported toward the southern part off the Banc d’Arguin, where coarse silt settles on the outer shelf and
upper slope, at least down to 600 m water depth. Particles of the fine silt fraction, estimated in terms of eolian material
collected aboard the research vessel, are thought to be exported further offshore as they correspond to grain sizes previously
reported from adjacent deep-sea sediments. These findings suggest that the interpretation of dust records from the continental
slope and rise off NW Africa must consider reworking and partitioning processes active on the Mauritanian shelf. |
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