Interaction of processes and importance of contourites: Insights from the detailed morphology of sediment Drift 7, Antarctica
M. Rebesco, A. Camerlenghi, V. Volpi, C. Neagu, D. Accettella, B. Lindberg, A. Cova, F. Zgur, Magico Party, 2007. "Interaction of processes and importance of contourites: Insights from the detailed morphology of sediment Drift 7, Antarctica", Economic and Palaeoceanographic Significance of Contourite Deposits, A. R. Viana, M. Rebesco
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As the definition of contourites has widened to embrace a large spectrum of sediments in so-called mixed systems, the distinction between contourites and turbidites has become at times vague. The case history of sediment Drift 7 off the Antarctic Peninsula is analysed in this paper in the light of newly acquired swath bathymetry data. The co-existence of various sedimentary processes is reflected in a complex morphology: erosional gullies produced by debris flows on the upper part of the continental slope; deeply incised channels at the slope base; main trunk-type inter-drift turbidity channels separating the drifts; slide scars; undulating depositional bedforms interpreted as bottom-current sediment waves; fluid escape structures perhaps associated with deep-water coral bioherms. The data suggest that Drift 7 is a genuine sediment drift in which bottom currents pirate the sediment of the turbidity currents. Finally, we propose that the control on location and elongation of the drift is inherited from an older margin structure. The relationships between bottom current and deposition are investigated through a comparison with the SE Greenland continental margin, an analogous counterpart in the northern hemisphere.
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There has lately been a growth in the number and level of studies of contourite deposits. Most recent studies of contourites have two major lines of interest. One, propelled by the oil industry's continuous move into increasingly deep waters, concerns their economic significance. The other involves the stratigraphic/palaeoceanographic record of ocean circulation changes imprinted on contourite deposits that can be a key to understanding better the climate-ocean connection. The application of many different theoretical, experimental and empirical resources provided by geophysics, sedimentology, geochemistry, petrology, scale modeling and field geology are used in the 16 papers of this volume, proposing answers to those two main aspects. The papers are subdivided into two major categories (economic interest and stratigraphic/palaeoceanographic significance), with case studies ranging from well-documented drifts to new examples of modern and fossil series, involving a large diversity of geographic and physiographic scenarios worldwide.