Distinguishing between Fine-Grained Turbidites and Contourites on the Nova Scotian Deep-Water Margin
- Dorrik A. V. Stow
Published Online: 29 APR 2009
Copyright © 1992 The International Association of Sedimentologists
Deep-Water Turbidite Systems
How to Cite
Stow, D. A. V. (1991) Distinguishing between Fine-Grained Turbidites and Contourites on the Nova Scotian Deep-Water Margin, in Deep-Water Turbidite Systems (ed D. A. V. Stow), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304473.ch12
Department of Geology, University of Southampton, UK
- Published Online: 29 APR 2009
- Published Print: 11 NOV 1991
Print ISBN: 9780632032624
Online ISBN: 9781444304473
- deep-water continental margins;
- Echogram and seismic profile characteristics;
- climbing ripples with no stoss side erosion;
- Nova Scotian Slope and Rise;
- Laurentian Fan and Scotian Slope and Rise, orienting to geographical north
Review of the criteria which have been proposed for distinguishing between the deposits of turbidity currents and bottom currents in deep water sedimentation shows no general agreement on their validity. It is important to compare fine-grained turbidites and contourites, to recognize that different turbidity current and bottom current mechanisms exist, and that their deposits may be closely interbedded in a continental rise environment.
Interbedded turbidites and contourites have been recognized in cores from the deep-water margin off Nova Scotia. The most useful criteria for distinguishing between the two deposits were found to be: (1) fining and sorting trends: perpendicular or parallel to the contours; (2) marked textural differences between interbedded turbidites and contourites indicating differences in source and transport distance; (3) mineralogy and textural composition: regional patterns indicating transport perpendicular or parallel to the contours; (4) grain fabric: indication of downslope or along-slope transport at the time of final deposition; (5) sedimentary structures: turbidites show a structural sequence and evidence of rapid burial; contourites are bioturbated and contain irregular lag concentrations of biogenic sand. Other criteria include grain-size parameters, and the regional setting, distribution and depositional rate of the various facies. With due care these criteria can be applied to other regions.
Previously used characteristics of silt-laminae abundance, layer thickness, heavy mineral cross lamination, sorting, and the nature of bed contacts are not applicable to fine-grained turbidites and contourites. Compositional criteria depend on regional features.