ABSTRACT

This paper presents the results of a series of detailed, small-scale geological studies on the continental slope off the northeastern United States. These studies show that slumping and turbidity currents are active and effective erosional agents in the area. Massive large-scale failure has occurred where the slope steepens from a gradient of 1.4° to 7.6°, producing scarps hundreds of meters in relief. Smaller scale slumps have occurred on other parts of the continental slope. Some of the material removed by slumping is emplaced at the foot of the continental slope as relatively intact blocks of 1 to more than 100 meters in thickness. Turbidity currents apparently initiated by slumping have eroded V-shaped gullies on the lower portions of the slope.

Bottom current activity is most influential at the shelf break, where it has sorted bottom sediments and resuspended fine material. Laboratory flume experiments and direct observations of the bottom, (using ALVIN and ALCOA SEAPROBE) indicate that the sediments on much of the continental slope generally are not normally affected by bottom currents. Biological activity, however, can cause both roughening and smoothing of the sediment surface, and the irregularities made by organisms will be reworked by currents. Biological production of fibrous structures can, on the other hand, make the sediment surface more resistant to erosion by bottom currents.