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Short-term sediment dynamics on a contourite body (off NW Iberia), Part I: Rapid changes of bottom-flow intensity during the past 50ka deduced from a sediment-core transect
Hanebuth, T.J.J.; Hofmann, A.L.; Lenhart, A.; Löwemark, L.A.; Schwenk, T.; Zhang, W. (2014). Short-term sediment dynamics on a contourite body (off NW Iberia), Part I: Rapid changes of bottom-flow intensity during the past 50ka deduced from a sediment-core transect, in: Van Rooij, D. et al. (Ed.) Book of Abstracts. 2nd Deep-Water Circulation Congress: The Contourite Log-book. Ghent, Belgium, 10-12 September 2014. VLIZ Special Publication, 69: pp. 33-34
In: Van Rooij, D.; Rüggeberg, A. (Ed.) (2014). Book of Abstracts. 2nd Deep-Water Circulation Congress: The Contourite Log-book. Ghent, Belgium, 10-12 September 2014. VLIZ Special Publication, 69. Ghent University, Department of Geology and Soil Science/Flanders Marine Institute (VLIZ): Oostende. xviii, 152 pp., more
In: VLIZ Special Publication. Vlaams Instituut voor de Zee (VLIZ): Oostende. ISSN 1377-0950, more

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Keywords
Author keywords
    Ocean bottom currents; Current-obstacle interaction; Eastern Atlantic; Late Quaternary

Authors  Top 
  • Hanebuth, T.J.J.
  • Hofmann, A.L.
  • Lenhart, A.
  • Löwemark, L.A.
  • Schwenk, T.
  • Zhang, W.

Abstract
    The sediment dynamics in a confined contourite system off NW Spain are reconstructed using high-res bathymetric mapping, seismic profiling, and sediment core transect. This depocenter and its 150m deep moat surround an 800m high obstacle. Since mid-Eocene, a pre-drift unit and two currentcontrolled contouritic units have formed. Fine-grained (10µm) basinwide current-influenced deposition was episodically interrupted by short-lasting high-energy conditions during MIS-3. High glacial and later Holocene periods show markedly calm conditions. The deglacial/early Holocene interval shows, in contrast, a pronounced increase in bottom-flow energy (70µm) with a waxing-and-waning dynamic from 17 to 5 cal ka BP. Process-based simulation demonstrates that not a water-mass core or boundary distributed those sands. Instead, pulse-like hydrographic fronts travelling inside the mixing zone of two water masses led to sand mobilization. Compared to paleoceanographic reconstructions, the downward-upward migrating MOW/LSW mixing zone is suggested as driving mechanism. A conceptional model shows how seafloor obstacles redirect and perturbate bottom flows with the special effect of oceanographic-front pulses occurring in the mixing zone. Front-driven secondary eddies on the contourite body itself provide an efficient mechanism for widespread sediment re-distribution.

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