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.

The Morphology of Two Transverse Channels on the Northeast Newfoundland Shelf

“…Holtedahl (1950Holtedahl ( , 1970) studied marginal channels off glaciated coasts and suggested that they were formed mainly by faulting at the contact between offshore sediments and continental 'shield' rocks. Grant (1971) examined the marginal channel off the Labrador coast and found no evidence of recent faulting. Grant suggested that preferential erosion by glaciation together with a tectonic 'hinge' zone near the contact of Palaeozoic strata with the Precambrian crystalline rocks, were the reasons for the formation of narrow marginal channels off glaciated coasts.…”

“…The Outer Shelf is underlain by Cenozoic strata (Grant 1971) on which Pleistocene ice sheets deposited a thin veneer of sediments during their retreat (van der Linden et al 1975).…”

“…Grant (1971) presented a comprehensive regional study of the geology of the Canadian margin of the Labrador Sea. Van der Linden (1975) summarized the history of the formation of the bedrock beneath the Labrador Sea.…”

Late Quaternary sedimentation, 50° N, North-East Newfoundland shelf

“…The outer shelf consists of shallow banks separated by deep channels cut into the Mesozoic-Cenozoic sequence. A veneer of Pleistocene sediments is recognised by seismic reflection profiling (GRANT, 1972), but its lithology and stratigraphy are virtually unknown. As a result, interpretations of Quaternary glacial ice extent on the North-east Newfoundland shelf are presently poorly constrained (e.g.…”

Taux d'enfouissement et altérations diagénétiques de matière organique azotée dans le nord-ouest atlantique subarctique =

“…The Labrador inner shelf is studded by a thin cover of till and of sediments derived from till by wave and iceberg reworking (Grant, 1972;Josenhans et al, 1986). The outer shelves of both Labrador and Greenland contain sequences of till and overlying stratified muddy 39 sediments of up to 300 m (Grant, 1972;Funder and Larsen, 1989;Josenhans et al, 1986).…”