Slumps on Upper Continental Slope, Northeastern United States--Observations from Submersible: ABSTRACT

Abstract

Many large sediment slumps have been mapped along the eastern continental slope of North America. Most of these features have been observed on high-resolution seismic profiles, but few have been observed from submersibles. Although seismic profiling is an effective means for mapping slumps, it has limitations. For example, it cannot be used to resolve small-scale features, especially on slopes greater than 15 to 20°. To define such features, slump and interslump areas along the uppermost continental slope in Lease Area 49 in the Baltimore Canyon Trough area and south of Georges Bank were examined by in-situ observations during 24 submersible dives. These dives revealed slump scars characterized by slopes of 20 to 45°, clay outcrops, and borings and depressions i habited by a diversity of megabenthic crustaceans and fish. Below the scars, step topography, reverse slopes, and hummocky seafloor were observed. Small slumps were observed at shallower depths (170 to 366 m) than previously had been resolved by seismic profiles. In contrast, areas with no slumps were characterized by smooth, gently dipping (5 to 8°) seafloor and sparse fauna. Slumps are potential geologic hazards to the siting of exploration wells, production platforms, and pipelines. Thus, this study is particularly relevant in light of recent discoveries of gas on the mid-Atlantic continental shelf. End_of_Article - Last_Page 529------------