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Lincoln F. Pratson1, Jasim Imran2, Gary Parker3, James Syvitski4, Eric Hutton4
(1) Duke University, Durham, NC
(2) University of South Carolina, Columbia, SC
(3) University of Minnesota, Minneapolis, MN
(4) University of Colorado, Boulder, CO

Abstract: Debris Flows versus Turbidity Currents: A Modeling Comparison of their Dynamics and Deposits

A numerical model of a debris flow is contrasted with the same type of model for a turbidity current to analyze the behavior and deposits of these two types of flows in ways that are difficult to accomplish by other means. The models demonstrate that the dynamics of a debris flow differ from those of a turbidity current because a debris flow tends to conserve its sediment mass while a turbidity current constantly changes its mass through erosion, deposition and entrainment. The resulting differences in flow behavior lead to fundamental differences in the distributions and geometries of the final deposits. The models predict that when begun on a slope that extends onto a basin floor, a debris flow will form a deposit that begins near its point of origin and gradually thickens basinward, ending abruptly at its head. By contrast, deposition from an ignitive turbidity current (i.e., one that causes significant erosion) will largely be restricted to the basin floor and will be separated from its origin on the slope by a zone of erosion. Furthermore, the turbidite will be thickest just beyond the slope base and thin basinward. These contrasting styles of deposition are accentuated when debris flows and turbidites are stacked.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana