The hypothesis that Newfoundland drifted from Ireland has been discussed since its presentation by F. B. Taylor in the first years of the century. The proof of the hypothesis will be sought in the continuity of structures to the edges of the continental shelves and their absence in the ocean floor, subjects suitable for geophysical exploration.

Newfoundland has a northwestern miogeosynclinal belt, essentially a platform relative to the central eugeosynclinal belt centered about Notre Dame Bay, and a southeastern platform, the Avalon platform. As the northeasterly trending structures of the northeastern coast should be projected beneath the submerged shelf, the geology of the Notre Dame Bay area came under study. In the 7 miles from the Dildo fault along the mainland of Newfoundland to the Lukes Arm right-lateral transcurrent fault through northern New World Island, there are three essentially north-facing, east-northeast-trending sequences of Ordovician and Silurian rocks, separated by the Cobbs Arm and Toogood faults. The oldest known rocks in these sequences are earliest Ordovician; the youngest are Silurian. Sole marks sh w that the flow of currents and gliding of slide masses generally were southwestward.

The largest volcanic- and plutonic-rock boulders are found in the northern of the three sequences in Silurian conglomerates with red matrix. Paleogeographic reconstruction of the Silurian shows that tilted fault blocks bounded northeast-trending troughs; Ordovician rocks in thrust sheets in western Newfoundland may have glided from such blocks. Accurate restoration of the paleogeography of the region requires re-placement of blocks that are separated by faults, some of which are transcurrent. The amount of displacement of most of these blocks is not known.

The tectonic history of central Newfoundland after Silurian deposition involves the formation of asymmetrical to recumbent north-facing folds that were further deformed to produce folds with steeply plunging axial lines and sinuous bed patterns on a map. High-angle, probably transcurrent, faults then formed and separated the sequences, which were farther offset a mile or so by other transcurrent faults. Details of structures along the Cobbs Arm fault zone came to be known because the economic importance of the Ordovician limestones led to their being drilled and mapped.

The stratigraphic and structural belts of northeastern Newfoundland have many similarities with those in the British Isles and in southern New England. If the belts in Europe and northeastern North America once were continuous, the stratigraphic belts have been offset about 500 miles by transcurrent faults in the North Atlantic. Similar right-lateral offset of stratigraphic-structural belts between Newfoundland and Cape Breton Island, and between that island and mainland Nova Scotia and New Brunswick, suggests the presence of other faults having similar trends. If the belts are not continuous beneath the ocean, the drift hypothesis requires separation of more than 1,000 miles in addition to the 500-mile right-lateral displacement.