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Small mounded contourite drifts associated with coral banks, Porcupine Seabight, NE Atlantic Ocean
Van Rooij, D.; Blamart, D.; Richter, T.; Wheeler, A.; Kozachenko, M.; Henriet, J.-P. (2004). Small mounded contourite drifts associated with coral banks, Porcupine Seabight, NE Atlantic Ocean, in: 32nd International Geological Congress, Florence, Italy, August 20-28, 2004. Abstract Volume. pp. Abstract 64-23
In: (2004). 32nd International Geological Congress, Florence, Italy, August 20-28, 2004. Abstract Volume. IGC: Florence. 2 vols pp.
Available in  Authors 
    Vlaams Instituut voor de Zee: Open Marine Archive 215035 [ download pdf ]
Document type: Summary
Keyword
    Marine/Coastal
Author keywords
    Deep-water corals Contourite Seismic stratigraphy British-Irish Ice Sheet Heinrich Events
Authors  Top 
  • Van Rooij, D.
  • Blamart, D.
  • Richter, T.
  • Wheeler, A.
  • Kozachenko, M.
  • Henriet, J.-P.
Abstract
    Numerous investigations on contourite drift systems have demonstrated they are dependant of a close interaction of topography, oceanography, sediment supply and climate. Most of these contourites have been reported in areas along the ocean margins directly influenced by the large oceanographic deep-water currents from the global conveyor belt. Here, we report on smaller-scale contourite deposits from Porcupine Seabight, a shallow embayment of the NE Atlantic slope, SW of Ireland.The Porcupine Seabight is a relatively shallow basin along the Irish Atlantic margin, well above the depth range of the large deep-water currents. It is characterized by the presence of deep-water coral banks which seem to be related to strong bottom currents. Within the Belgica mound province, located on the eastern slope, various observations demonstrate the presence of a northward flowing bottom current. These currents seem to be created by a complex interaction of the water mass characteristics, tidal influences, and seafloor topography. Therefore, the present-day seafloor around these coral banks is covered with a thin contourite sand sheet with sand ripples, barchan dunes and sand ribbons.Very-high resolution seismic stratigraphy of the area demonstrates that the coral banks are seated on a complex topographic surface, created by a probable Intra-Pliocene erosion event. The resulting (early Quaternary) seabed morphology features a wide variety of obstacles which could foster a topographic steering of bottom currents, affecting the geometry of the sediment body deposited within this area. Several sediment mounds can be observed within the vicinity of the coral banks.A 26 m Calypso core taken in such a drift mound shows the variability of the bottom currents throughout the last glacial period. The glacial part of the core (Marine Isotope Stage 4-2) is a muddy contourite with a high content of ice-rafted debris. Sortable silt data shows several periods of bottom current enhancement which might be linked with warmer (interstadial) periods and an inferred influx of Mediterranean Outflow Water. The lower part of the core is a sandy foraminiferal deposit resembling the present-day seafloor sediments. Stable isotope and micropaleontological data indeed confirm these are interglacial deposits (Marine Isotope Stage 5d-5a?), demonstrating high benthic currents under a hydrodynamic environment similar to present-day conditions.
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