North American Continent-Ocean Transects Program Transect D4: Rifted Continental Margin Off Labrador
C. E. Keen, R. T. Haworth, 1985. "North American Continent-Ocean Transects Program Transect D4: Rifted Continental Margin Off Labrador", D-4 Rifted continental margin off Labrador, C. E. Keen, R. T. Haworth
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The Labrador margin is the result of continental break-up between Greenland and North America in Late Cretaceous time. This margin formed by rifting of Precambrian Shield rocks (Fig. 1). Four Precambrian Shield Structural Provinces are represented on the geological map: Nain, Makkovik, Churchill and Grenville Provinces. The Nain Province (Taylor, 1972; Umpleby, 1979) probably extends offshore beneath the region of the D4 Transect. It consistsprimarily of Archean rocks and is older than either the Churchill Province to the south and west or the Grenville Province to the south. South of the Nain Province, the Makkovik Province was affected by Hudsonian (1600 Ma) deformation and metamorphism, which characterizes much of the nearby Churchill Province. The Grenville Front separates the older rocks of the Churchill and Makkovik Provinces from the younger Grenville Province (1000 Ma or less). The latter may represent an overthrust orogenic belt (Wynne-Edwards, 1972).
The Paleozoic history of the region is not well known. Paleozoic rocks are virtually absent from the mainland. Thin Paleozoic sediments have been sampled locally in the bottom of deep boreholes in the continental shelf (Umpleby, 1979). This may reflect the presence of a Paleozoic epicontinental seaway in the region, but its tectonic significance and extent are unknown. No Paleozoic rocks were sampled near the D4 Transect.
Figures & Tables
DNAG Transect D-4. Part of GSA's DNAG Continent-Ocean Transect Series, this transect contains all or most of the following: free-air gravity and magnetic anomaly profiles, heat flow measurements, geologic cross section with no vertical exaggeration, multi-channel seismic reflection profiles, tectonic kindred cross section with vertical exaggeration, geologic map, stratigraphic diagram, and an index map. All transects are on a scale of 1:500,000.