James P. M. Syvitski1, Damian B. O'Grady1, Eric W. H. Hutton1
(1) University of Colorado, Boulder, CO
ABSTRACT: Equilibrium Slopes of Continental Margins
Physics
-based numerical models provide for an ideal platform to examine the response of morphology to changing sedimentary conditions. Numerical experiments were conducted with the multi-process, basin-fill model SedFlux, to evaluate the evolution of the two-dimensional shape of siliciclastic continental slopes. The experiments were able to isolate the impact on the shape of the slope profile, of river discharge, ocean storms, sediment failure, gravity flows, subsidence, and sea level fluctuations. Numerical experiments were designed to discover how continental margins prograde and aggrade through time.
Hemipelagic sedimentation along with shelf storms produces simple clinoforms. Oblique clinoforms are associated with low-energy conditions; sigmoid geometries are associated with a more energetic ocean. Ocean storms enhances the stability of the upper continental slope and the shape of the shelf-break rollover. Slope failure steepens the upper continental slope and creates a more textured profile. Debris flows accumulate along the base of the continental slope, leading to slope progradation. Turbidite deposition principally occurs on the basin floor and much of the continental slope remains a zone of erosion and sediment bypass. Sea level and flexural subsidence show smaller impacts on the shape of the slope. Ocean depth has a profound influence on the steepness of the equilibrium profile.
Type margins eventually develop an equilibrium profile, i.e. a morphology that changes little once it is achieved, and is no longer under the influence of the paleo basin bathymetry. SedFlux provides a means to determine the time to achieve an equilibrium profile, given an initial set of boundary conditions. It allows us to explore which continental margins are yet to achieve an equilibrium profile. The equilibrium profile concept lends itself to analytical solutions to slope profiles and the potential for developing inverse methods to interpret initial conditions.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado