Abstract: Sedimentary Processes on Continental Slope off New England

David A. Ross, Joseph C. MacIlvaine

A detailed small-scale geologic study of the continental slope off northeastern United States confirmed that slumping and turbidity currents are active and effective erosional agents. Massive large-scale failure has occurred where the slope steepens from a gradient of 1.5 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 1 to 100+ m thick. Turbidity currents, apparently initiated by slumping, have eroded V-shaped gullies on the lower parts 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 normally are not affected by bottom currents.

Biologic activity can cause both roughening and smoothing of the sediment surface. Tracks made on the bottom by organisms can produce small-scale roughness, of which the larger features will be reduced by reworking by currents. Biologic production of fibrous structures, however, may help make the sediment surface resistant to erosion by bottom currents.

AAPG Search and Discovery Article #90961©1978 AAPG Annual Convention and Exhibition, Oklahoma City, Oklahoma