Since 1978, the U.S. Geological Survey has been conducting a study of the Atlantic Continental Slope between Linden kohl and South Toms Canyons, offshore New Jersey, to determine the nature of potential geologic hazards to hydrocarbon exploration and exploitation. The study has progressed from characterization of the near-surface stratigraphy, using single-channel seismic-reflection data and piston cores, to detailed geomorphologic studies using midrange sides can-sonar coverage, and finally, to targeted observations from deep-diving submersible. The seismic-reflection data and cores have shown that unconsolidated Pleistocene sediments as much as 400-m thick cover the upper and mid slope, and that identifiable slump or slide features occupy only a small part of the slope area mapped. Much of the slope is mantled by a veneer of fine-grained Holocene sediment. We inferred that the slope topography is largely relict from late Pleistocene or early Holocene time and that present conditions of geomorphic change are probably quiescent. Subsequently acquired monographs from a deep-towed side scan-sonar system having a 5 km swath show such features as a debris field at the mouth of South Toms Canyon, oddly shaped features on the mid and lower slope suggestive of slump or slide origin, and areas of an enigmatic pattern of down slope-trending "stripes". Most recently, four dives in DSRV ALVIN during July 1981 on the area of Tertiary outcrops of the lower slope revealed 10-m-high talus blocks at the base of the slope, cliffs and steep-walled valleys having as much as 40 m relief, control of cliff surfaces and the, shapes of valleys by sets of joints, occurrences of classic dikes, and sets of parallel, 4to- 12-m-deep furrows (probably erosional) spaced 2050 m apart in Eocene calcareous clay stone at the mouth of Berkeley Canyon. In some places, the smaller scale topography of the lower slope appears fresh; some planar surfaces are unbowed by organisms or scoured, and some of the talus fragments on the upper rise appear to be recent. However, a thin cover of fine grained flocky sediment on horizontal surfaces implies that present-day activity is either not vigorous or is intermittent. Nevertheless, canyons and valley trawlers should probably be viewed with caution if considered for structure sites.
The prospect of extensive hydrocarbon exploration and potential production on the Continental Slope off the eastern United States has created a need for surgical geologic studies of the slope -- a large, deepwater area which has previously received relatively little attention from marine geologists, particularly at the level of detail required for engineering analysis or studies of geologic hazards. A study of a series of cable breaks off the Grand Banks in 1929 (Heezen and Ewing, 1952) led to the specter of slumping and turbidity currents as potentially catastrophic events on the Continental Slope. The identification of probable slump dep9sits and scars in seismic-reflection profiles (Rona and Clay, 1967; Uchupi, 1967; Emery and others, 1970;
