Published 1995 as part of Memoir 65
Copyright © 1995 The American Association of Petroleum Geologists.   All Rights Reserved.

Geological Survey of Canada

Calgary, Alberta

Canada

The Ordovician (upper Arenig-Llanvirn) Bay Fiord Formation is one of three widespread evaporite units known to have profoundly influenced the style of contractional tectonics within the Innuitian orogen of Arctic Canada. In the western Arctic Islands, the salt-bearing Bay Fiord Formation has accommodated buckling and mostly subsurface thrusting in the west-trending Parry Islands foldbelt. A characteristic feature of this belt is a stratigraphic succession more than 10 km thick featuring three rigid and widespread sedimentary layers and two intervening ductile layers (lower salt and upper shale). The ductile strata have migrated to anticlinal welts during buckling. Other features of the foldbelt include (1) an extreme length of individual upright folds (up to 330 km), (2) extreme foldbelt width (up to 200 km) governed by the distribution of underlying salt, (3) an equal occurrence of stacked and duplexed forethrusts and backthrusts (some carrying salt upsection) within anticlines, (4) modest overall shortening (up to 11%), (5) a shallow dipping salt décollement system (0. 1^°-0. 6^°) that has also been folded in the hinterland and later extended, and (6) a complete absence of halokinetic piercing diapirs. The progression from simple thrust-fold structure on the foldbelt periphery to complex in the interior provides a viable kinematic model for this and other contractional salt provinces. One feature of this model is a single massive triangle zone structure (passive roof duplex) that may envelop the entire 200-km width of the foldbelt and underlie an area exceeding 52,000 km².