ABSTRACT

Contemporary submarine slumps have previously been discussed in the geological literature primarily as a mechanism to explain otherwise anomalous topographic or sedimentary features observed on the sea-floor. In contrast, quantitative soil mechanics techniques of measuring the strength properties of sediments are used in this preliminary geological evaluation of some major marine provinces as source areas of submarine slumps and their consequent turbidity currents.

Direct shear and vane shear tests were made on undisturbed samples from the deep North Pacific, from continental and basin slopes, and from the continental shelf off California. Pre-existing strength data are summarized for comparison.

Sediments which would be theoretically stable to great thicknesses even on very steep slopes were found to predominate in all of these areas. It is concluded that the kind and rate of sedimentation required to produce unstable slopes occurs only in specialized areas of relatively rapid accumulation. These include deltaic and canyon head environments on the inner shelf, and probably also canyon or gulley walls on the open shelf and slopes. The normal open shelf and the deep-sea are believed to be nearly free of slumping.

More study of slope sediments is required particularly in and around canyons. Large scale progressive slumping offers a mechanism for failure of otherwise stable, relatively gentle slopes. The possibility of this process should be investigated in areas of suspected extensive slope failure.