Hemipelagic advection and periplatform sedimentation
In: Hüneke, H.; Mulder, T. (Ed.) (2011). Deep-sea sediments. Developments in Sedimentology, 63. Elsevier: Amsterdam. ISBN 978-0-444-53000-4. xiv, 849 pp., more
In: Developments in Sedimentology. Elsevier: New York; London; Amsterdam. ISSN 0070-4571; e-ISSN 2352-2844, more
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| Abstract |
In areas close to continental margins, where siliciclastic supply is abundant, pelagic rain of biogenic materials is substantially diluted by clay- and silt-sized terrigenous components. These muds are known as hemipelagic sediments. In the vicinity of shallow-water carbonate platforms, in analogy, pelagic rain is diluted by neritic debris supplied from the carbonate-platform tops and margins to the adjacent deep-ocean water column. Those oozes are termed periplatform carbonates. In both cases, open-ocean materials and shelf- or platform-derived particles collectively rain down through the lower water column and settle onto the sediment.This chapter presents an overview of the large diversity of processes and principal factors that control hemipelagic advection and periplatform settling and determines the character and distribution of the resulting deep-sea sediments. River discharge, dust load, or sea ice and icebergs are the main sediment carriers, which supply sediment onto the shelves. There, complex processes of differential dispersal, bypassing, or resuspension and redeposition affect the sedimentary materials before they are finally transferred to the continental margins. Therefore, shelves may act as major filters as well as conduits for siliciclastic-sediment transfer into the deep sea. Off-shelf transport of carbonate-platform materials is mainly achieved by storms or wind- and tide-driven advection and can be temporarily forced by density cascading and geostrophic currents. Special attention is given to compositional variations in the shallow-water-derived materials since these mainly reflect changes in the source region or in the bypass area on the shelf. For the accumulation of both types of sediments, hemipelagic muds and periplatform oozes, the impact of sea-level fluctuations and climatic changes is very high and outlined in the discussion. |
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