A newly developed mid-range sidescan sonar system having a range of 2.5 km/side was used in conjunction with long-range, GLORIA II, sonographs (maximum range 22 km/side) and high-resolution seismic profiles to map parts of the continental slope and upper continental rise between Cape Hatteras and the Blake Spur, off southeastern United States. A 60-m-high scarp that traverses the slope to encircle a near-surface diapir complex was identified from seismic-reflection records and traced laterally for approximately 30 km by using GLORIA II data. More detailed mid-range sidescan sonographs of the area show detached-block slide paths cut into the sea floor, which have scarps 15 to 20 m high and areal extents of at least 3 to 5 sq km. These slide blocks appear to originate at th scarp face and extend downslope to lobate deposits of apparent sediment debris, or to areas beyond our data coverage. Such features as overlapping slide paths and minor sediment failures on the scarp face revealed in the images indicate the relative chronology of events. The position of the scarp relative to the near-surface diapir complex, and its presence on an otherwise featureless and gently sloping segment of the continental slope, suggests that the scarp was created during the formation of the diapir complex, when withdrawal of salt at depth led to local oversteepening of the slope surface and consequent failure by slumping and surficial slides.

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