The Continental Margin Off Labrador and Eastern Newfoundland–Morphology and Geology

Abstract

Seismic profiler surveys have defined the landward limit of presumed Mesozoic–Cenozoic deposits on the continental shelf off Labrador and eastern Newfoundland. Along the Labrador coast the contact of these deposits with Precambrian rocks coincides with a pronounced 'marginal channel'; off eastern Newfoundland their contact with rocks of the Appalachian System is marked by a landward-facing escarpment. The physiographic relief characterizing this contact zone reflects erosional exploitation of the associated contrast in erosional susceptibility. The chief erosional agent is considered to have been the Quaternary glaciers. The marginal channel off northern Labrador is indicated as a zone of major faulting, which probably further enhanced the erosional vulnerability. The transverse depressions cutting the outer shelf off Labrador and Newfoundland are likewise considered to be zones of structural dislocation, which have been physiographically emphasized through processes of erosion.Integration of the seismic profiler results with other geophysical and geological data from the study region consistently supports the concept that the morphology of the continental margin expresses fundamental elements of geologic structure. Available evidence can apparently be reasonably synthesized in terms of a structural model based upon differential vertical movements of segments of continental crust. By this approach the structure of the continental margin north of the Grenville Front off Labrador may be very different from that of the continental margin bordering the western Atlantic Ocean to the south. In addition, the continental fragments represented by Orphan Knoll and Flemish Cap are indicated as having experienced only vertical displacements during postulated episodes of late and post-Cretaceous sea-floor spreading.