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ABSTRACT: The North American Atlantic Outer Continental Margin Landslides Data Base: Summary and Observations

James S. Booth, Dennis W. O'Leary

A compilation of published data from 179 Quaternary mass movement features was analyzed to determine the common attributes of the slides, to reveal general trends, and to classify and compare slide types. The data set was derived primarily from high-resolution, seismic-reflection data and sidescan-sonar images.

In general, evidence of slope failure is found throughout the length of the margin and in all water depths. Slides have occurred on slope angles ranging from 1° to 30° (avg. ^sim5°); they vary in width from 0.2 to 50 km (avg. ^sim4 km) and in length from 0.3 to 380 km (avg. ^sim10 km) and have been reported to be as thick as 650 m. They are slightly more prevalent on "open" slopes than in other physiographic settings (e.g., canyons, ridges, spurs) and more commonly translational than rotational (i.e., slumps). The slides show no striking affinity for a particular depth range, either in the data set as a whole or when analyzed in terms of physiographic setting, size, slope angle, or other basis for classification.

Comparison of slides found on the "open" slope with those found within canyons shows that the average "open" slope slide tends to occur at lower slope angles and is much larger (by an order of magnitude) than the average canyon slide. Regardless of the physiographic setting or other characteristic, large-scale slides (area >100 km2) rather than small-scale slides (area <10 km2) tend to be associated with gentle slopes (^sim3-4°) Similarly, slides generated on steep slopes (>=10°), regardless of other attributes, tend to be small (avg. area <5 km2).

With few exceptions, comparisons between slide categories show only minor differences. The occurrence of such a variety of slope failures at low slope angles, which are apparently otherwise devoid of distinct attributes or trends, remains an enigma and is a focus of our current research.

AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990