--> Abstract: Processes and Modeling of Deep Water Flows: the Evolution of Hybrid and Transitional Flow Types; #90063 (2007)

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Processes and Modeling of Deep Water Flows: the Evolution of Hybrid and Transitional Flow Types

 

Haughton, Peter1, William McCaffrey2, Christopher Davies1, Simon Barker3 (1) University College Dublin, Dublin, Ireland (2) University of Leeds, Leeds, United Kingdom (3) BG, Berkshire, United Kingdom

 

Gravity transport in deep-water basins is often ascribed to either debris flows or turbidity currents. However, cogenetic flows involving linked turbulent and laminar components, or clay-prone transitional flows characterised by mixed or oscillating behaviour, are common. The former can give rise to turbidite-debrite couplets, the latter to banded and other ‘slurry' fabrics, although the term slurry has been loosely used and is probably best avoided. Linked and transitional flows are increasingly recognised in both outcrop and cores, and curiously seem to be best developed in distal and lateral fan settings. Care must be taken to distinguish genuine hybrid flow components from partial remobilisation and secondary mixing bodies (sand autoinjection and substrate deformation) with which they may be confused. In some systems, single events preserve evidence of flows evolving from turbulent through transitional to laminar flow regimes, suggesting longitudinal suppression of turbulence and flow transformation. Many of these hybrid event beds seem to be related to periods of up-dip incision, either on inbound slopes or on the basin floor. Local erosion may choke and collapse part of a sandy turbidity current to partition the flow into a relatively low velocity debris flow and/or transitional flow that propagates over, and interacts with, the just-deposited turbidite sand. The presence of these hybrid beds may identify disequilibrium slopes up-dip that were steep enough to promote significant flow incision. Where hybrid beds dominate the distal fan stratigraphy, this implies parts of the flow routeways were continually out-of grade to force repeated flow partitioning.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California