Seismic-profiler investigation of the continental margin northeast of Newfoundland

Abstract

Continuous seismic profiler recordings over the continental shelf northeast of Newfoundland show an accumulation of unconsolidated sediments ranging in thickness from 30 to 150 m, unconformably over-lying bedrock that dips gently eastward toward the continental slope. The distribution of these unconsolidated sediments indicates that the banks that compose the 'shelf-edge rise' are not primarily morainal material, but rather they are areas of positive relief on the bedrock surface. Anomalous strike-dip relationships associated with these bank areas suggest that they may also have structural significance. The underlying bedrock layers are truncated by the continental slope, and there is reversal in the dip of these layers from eastward to westward beneath the slope. The axial zone of the resulting fold apparently coincides very nearly with the axis of a large magnetic anomaly that extends along the continental margin in this region. A Tertiary to post-Tertiary age is suggested for the fold, as well as the structural disturbance associated with the topographic relief on the continental shelf. Within the continental rise an area of irregular bottom topography is considered to be due to the accumulation of large masses of sediment by slumping. Subbottom reflectors at depths beyond the continental rise show crumpling, which is assumed to be further evidence of mass-movement due to gravity. Superficially, the continental margin northeast of Newfoundland appears similar to parts of the continental margin to the south, on the flank of the Appalachian structural complex.