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Trapping of sustained turbidity currents by intraslope minibasins

Lamb, Michael P. and Toniolo, Horacio and Parker, Gary (2006) Trapping of sustained turbidity currents by intraslope minibasins. Sedimentology, 53 (1). pp. 147-160. ISSN 0037-0746.

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Depositional turbidity currents have filled many intraslope minibasins with sediment creating targets for petroleum exploration. The dynamics of sustained turbidity currents and their depositional characteristics are investigated in a scaled physical model of a minibasin. Each turbidity current deposited a downstream thinning wedge of sediment near the inlet. Farther downstream the turbidity current was ponded by a barrier. The ponded part of the turbidity current was separated from the sediment-free water above by a relatively sharp, horizontal settling interface indicating highly Froude-subcritical flow. The very slow moving flow within the ponded zone created conditions for the passive rainout of suspended sediment onto the bed. In the lower part of the ponded zone, the concentration and mean grain-size of the sediment in suspension tended to be relatively uniform in both the vertical and streamwise directions. As a result, the deposit emplaced in the ponded zone showed only a weak tendency toward downstream fining and was passively draped over the bed in such a way that irregularities in the inerodible bed were accurately reflected. The discharge of suspended sediment overflowing the downstream end of the minibasin was significantly less than the inflow discharge, resulting in basin sediment trapping efficiencies >95%. A simple model is developed to predict the trapping of sediment within the basin based on the relative magnitudes of the input discharge of turbid water and the detrainment discharge of water across the settling interface. This model shows a limiting case in which an intraslope basin captures 100% of the sediment from a ponded turbidity current, even through a succession of sustained flow events, until sediment deposition raises the settling interface above the downstream lip of the minibasin. This same process defines one of the mechanisms for minibasin filling in nature, and, when this mechanism is operative, the trap efficiency of sediment can be expected to be high until the minibasin is substantially filled with sediment.

Item Type:Article
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Lamb, Michael P.0000-0002-5701-0504
Parker, Gary0000-0001-5973-5296
Additional Information:© 2005 International Association of Sedimentologists. Manuscript received 4 September 2003; revision accepted 2 August 2005. Article first published online: 22 December 2005. This research was supported by the St. Anthony Falls Oil Consortium (Anadarko, ChevronTexaco, ConocoPhillips, ExxonMobil and Japan National Oil Company) and the Office of Naval Research STRATAFORM program (grant to G. Parker). We thank Jeff Marr, Ben Sheets, Nikki Strong and Jake Violet for assisting with the experiments. Chris Paola added significantly through many valuable discussions. Finally, we thank Tom Hickson, whose initial experiments inspired many of the ideas presented in this paper and for providing us with Figs 1 and 3. An earlier version of this paper greatly benefited from reviews by Peter Haughton, Stuart McLelland, and an anonymous reviewer.
Funding AgencyGrant Number
St. Anthony Falls Oil ConsortiumUNSPECIFIED
Office of Naval Research (ONR)UNSPECIFIED
Subject Keywords:Froude number, intraslope, minibasin, ponding, turbidite, turbidity current.
Issue or Number:1
Record Number:CaltechAUTHORS:20110228-073956042
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Official Citation:LAMB, M. P., TONIOLO, H. and PARKER, G. (2006), Trapping of sustained turbidity currents by intraslope minibasins. Sedimentology, 53: 147–160. doi: 10.1111/j.1365-3091.2005.00754.x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:22532
Deposited By: Benjamin Perez
Deposited On:28 Feb 2011 18:07
Last Modified:09 Mar 2020 13:19

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