Abstract

The model applies plate-tectonics to explain the geologic evolution of southeastern Atlantic Canada and northwestern Africa. The North Atlantic may have opened and closed several times from the middle Cryptozoic to the present. Closings of the ocean caused collisions between continents and also island arcs. Openings were ragged so that parts of one continent were transposed to the other, and sialic fragments became offshore micro-continents. Africa has progressively lost increments of continental crust to North America.Precambrian blocks of southeastern Atlantic Canada may be remnants of an African shelf. which was crumpled during a billion-year old continental collision (Grenville orogeny). After ragged rifting during the Late Precambrian these fragmentary blocks were carried eastward as micro-continents off Africa. Both early (Danakil Alps of the Red Sea) and late-stage (Canary Islands) recent analogues appear valid. The micro-continents ponded turbidites, which formed rise-complexes off Africa. Continental glaciations in the Late Precambrian and Late Ordovician not only make excellent inter-regional chronostratigraphic units in almost unfossiliferous strata. but also may confirm the African origin of Nova Scotia. Subducting plate-margins increased offshore volcanism and narrowed the Paleozoic Atlantic. Late Paleozoic continental collision again between Africa and North America sandwiched the micro-continent, telescoped the sedimentary/volcanic complexes, and flooded the sutured area with granodiorite. Middle Carboniferous carbonates and sulfates record vestiges of the Paleozoic Atlantic, and mixing of the Euro-African fauna with that of the western Paleozoic Atlantic of the northwestern Appalachians. The Atlantic was closed at least along the latitude of Atlantic Canada and Morocco. During the Mesozoic, an accreting margin uplifted this area, quickened redbed deposition and volcanism, initiated restricted marine sedimentation, and inaugurated the present North Atlantic east of the African remnant of southeastern Atlantic Canada.

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