Sediment Waves: Are They Cyclic Steps or Antidunes?

S. Kostic
San Diego State University, San Diego, CA, [email protected]

Numerical models provide an invaluable tool for the interpretation and prediction of deep-sea sedimentary systems because they link the geometrical characteristics of turbidity current deposits to the properties of the flows that sculpted them. Recent research suggests that the most commonly observed sediment wave pattern on the seafloor consists of cyclic steps. Sediment waves in a submarine environment invariably have been characterized as antidunes or antidune-like features associated with turbidity currents. In this analysis sediment waves that consist of cyclic steps are compared and contrasted to their close relatives, sediment waves consisting of upstream-marching antidunes. The numerical model is used to simulate cyclic steps associated with the three most common types of slope breaks in a submarine environment. The results of the numerical simulations provide clear evidence that net-depositional cyclic steps similar to sediment waves observed on channel levees have to be predominantly composed of mud. The latest experiments on wedge-shaped sedimentary deposits in minibasins, which also produced depositional cyclic steps, unambiguously support the numerical predictions. On the other hand, net-erosional cyclic steps similar to cyclic scours observed along the thalwegs of some steep canyons and along channels created at partial channel avulsions have to have a sand-rich composition.

AAPG Search and Discovery Article #90088©2009 Pacific Section Meeting, Ventura, California, May 3-5, 2009