--> Abstract: Turbidite Deposition: The Role of Initiating Process and Slope Morphology from Mid-Latitude Continental Margins, by David J. Piper and William R. Normark; #90078 (2008)

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Turbidite Deposition: The Role of Initiating Process and Slope Morphology from Mid-Latitude Continental Margins

David J. Piper2 and William R. Normark1
1US Geological Survey, Menlo Park, CA
2Geological Survey of Canada (Atlantic), Dartmouth, NS, Canada

The initiation mechanisms for late Quaternary turbidites on the eastern Canadian and western U. S. margins are compared. Numerous local studies in both regions have inferred initiation mechanisms for turbidity currents, based on sparse real-time data for historical flows, and inferences based on the age and contemporary paleogeography, erosional features, and depositional record of well-studied flows. In both areas, three major types of initiation process are recognised: transformation of failed sediment, hyperpycnal flow from rivers or ice margins, and resuspension of outer shelf sediment by oceanographic processes. Most high-concentration flows result from hyperpyncal supply of hyperconcentrated bedload, or liquefaction failure of coarse-grained sediment, and tend to deposit in slope conduits and gradients < 0.4° at the base of slope and on mid fan areas. Highly turbulent flows from transformation of prolonged retrogressive failures and from ignitive flows triggered by oceanographic processes tend to cannibalize these more proximal sediments and deposit on gradients of < 0.2° on basin plains. Most sediment failures do not result in large turbidite beds.

Initiation mechanism exerts a strong control on the duration of turbidity-current flows. In most basins, there is a complex feedback between different types of turbidity- current initiation and the associated slope morphology. It is therefore unlikely that there is a simple relationship between the type of turbidite bed (e.g. a classical Bouma sequence turbidite) and an initiating process (e.g. sediment failure).

 

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas