Attributes of Preserved Stratigraphy Associated with Erosional Sinuous Submarine Channels: An Experimental Perspective

Acoustic imaging techniques provide ample static information on modern and ancient sinuous submarine channels. However, the morphodyamics of these channels remain poorly understood and difficult to document. We present a suite of experimental observations that directly connect the evolution of sinuous subaqueous channels to the properties of modifying erosional turbidity currents. Our original channel cut into a weakly cohesive substrate consisting of a mixture of plastic grains and clay. This channel has a sinuosity of 1.03, a width-to-depth ratio of 5:1, and was constructed on a regional slope of 10 degrees. Currents evolved the form of the channel through persistent erosion at the outer banks of bends and deposition along the inner banks of bends. These turbidity currents transported sediment over the entire range of styles, from full suspension to pure bedload.

The eroding channel bed beneath the paths traveled by the high-velocity cores of currents was characterized by connected grooves and scour pits. Sedimentation in the channel was limited to: (a) topographic lows which collected the coarse fraction of sediment travelling through the channel as bedload; and (b) low-velocity zones which trapped suspended sediment where flows separated from the inner banks of the channel. With increasing channel bend curvature, the degree of flow separation due to current run-up at the outer bank increased, reducing the amount of turbid flow entering the low-velocity zones and decreasing sedimentation rates at the inner banks of bends. We will synthesize high-resolution bathymetric maps, time-lapse photographs, spatial sorting of deposited grain-sizes, and sedimentary structures preserved in the dissected deposits so that attributes of the preserved stratigraphy can be related to the flow- and sediment transport-fields of currents as the planform of the sinuous subaqueous channel evolved.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California