Introduction

The origin of submarine canyons of the U.S. Atlantic continental margin remains a subject of controversy and speculation. Assumptions about their origin and function are based mainly on bathymetry and spatial relations observed on the middle to upper slope and on relations to stratigraphy of the rise, revealed chiefly by high-resolution seismicreflection data. The largest canyons along the Atlantic margin (and elsewhere) are more or less aligned with the mouths of major rivers, except along Georges Bank. This association has led to the most generally accepted explanation for the origin of the canyons: that they originated by collapse of deltaic sediments deposited by rivers at the shelf edge during eustatic lowstands (Vail, Mitchell, and Thompson 1977; Reineck and Singh 1980; Coleman, Prior, and Lindsay 1983). The collapse, or slumping, is thought to have generated turbidity currents having sufficient erosive power to have carved canyons across the slope and, in many cases, out across the upper rise.

However, sidescan sonar surveys undertaken along the U.S. Atlantic slope during the 1970s (Twichell and Roberts 1982; Scanlon 1984) showed that extensive canyon erosion has occurred along the lower to middle slope and that a link to the shelf is not required for canyon development.