ABSTRACT

The westward extension of the Peace River Arch of Alberta can be recognized in Vreeland and Ice Mountains in the Monkman Pass area of the Rocky Mountains of northeastern British Columbia. A late Hadrynian paleosurface on Vreeland and Ice Mountains, which is developed on foliated polymictic conglomerates of the lower part of the Windermere Supergroup, is overlain by carbonates of latest Hadrynian age (Vendian?). These carbonates lack the foliation of the underlying polymictic conglomerates, and are separated from the latter by a high-angle unconformity. Sedimentary control exerted by the Peace River Arch within the Rocky Mountains is seen in the pattern of reefing design from within the uppermost Precambrian strata to as high as the Upper Devonian. Lower Cambrian archaeocyathid reefs trace the western extension of the Arch across the Rocky Mountain Trench west to the Barkerville area of British Columbia. Laramide folding of the late Hadrynian paleosurface seems to be relatively gentle and the mountain ranges of Phanerozoic rocks lack the extreme compression found in the southern Canadian Rockies. The Vreeland - Ice Mountain uplift of the Monkman Pass area seems to lie within the westward extension of the Athabasca mobile zone of the Churchill thermal province that underlies the western Plains. The initial development of the foliation in the polymictic conglomerates of the Vreeland High is inferred to be the product of a late Precambrian event, occurring later than the East Kootenay orogeny.