A Preliminary Tectonic Map of the Canadian Appalachian Region Based on Age of Folding

CIM Bulletin, 1961


A new style of tectonic map based on age of folding has been prepared for the Canadian Appalachian region as part of the Tectonic Map of Canada Project. This style of map provides a clearer picture of the tectonic history of the region than any method hitherto attempted. Precambrian blocks that were relatively unaffected by Palaeozoic deformation are distinguished on the Great Northern Peninsula and in the Conception Bay region of Newfoundland. K/ A age determinations suggest that these blocks were intruded and metamorphosed during Grenville orogeny. Other Grenville-like rocks, on Cape Breton Island and in New Brunswick, were more actively involved in subsequent Palaeozoic orogeny. Taconic orogeny, the first phase of Palaeozoic deformation, took place in Middle and/ or Late Ordovician time and was accompanied by intrusion of ultrabasic rocks. Evidence of the orogeny occurs in Quebec, New Brunswick, Cape Breton Island ( ?) , and throughout central and part of the west coast of Newfoundland. Mainland Nova Scotia was not folded during Taconic orogeny. A narrow belt of the Taconic deformed zone, along the south shore of St. Lawrence River and part of the west coast of Newfoundland, was probably not subsequently deformed. However, all other parts of the Canadian Appalachian region were subjected to Acadian orogeny. This second phase of Palaeozoic deformation reached its climax about Middle Devonian time. Widespread granitic intrusion accompanied Acadian orogeny and K/ A dates suggest that most granitic rocks of the region are Devonian. Late Palaeozoic folding, the third phase of deformation, was restricted to a narrow belt which extends from the Bay of Fundy through Cape Breton Island northeast to Cape Anguille and beyond to White Bay, Newfoundland. Folding of the Carboniferous rocks varied in time and intensity from place to place within this belt. It was chiefly controlled by movements of rigid blocks of pre-Carboniferous rocks. Late Pennsylvanian (Pictou) sediments and block-faulted Triassic red beds and basic volcanics cover strata of this Late Palaeozoic folded belt.
Keywords: Acadian orogeny, Late Palaeozoic Folded Zone, Lower Devonian, Ordovician, Taconic orogeny, Appalachians, Canadian, Folding, Maps, New Brunswick, Newfoundland, Phase, Rock, Rocks, Tectonics