ABSTRACT

The eastern margin of the Cordilleran foldbelt of northern Canada is characterized by bundles of folds which are arcuate in plan and which form prominent salients and re-entrants in the mountain front. They are due primarily to the Laramide orogeny. Within these bundles may be observed arrays of folds which are characteristically right-hand en echelon in the south flanks of the salients and left-hand in the north. Thus between the 60th Parallel and Beaufort Sea the arrays are alternately right- and left-handed on the flanks of Mackenzie and Brooks Range arcs and appear to identify a regional, basic, Laramide kinematic and dynamic pattern for this exposed part of the crust. Application of the model studies of Tokuda (1926-27) and Campbell (1958) suggests the possibility of differential northeastward transport of the Hadrynian and younger, layered sedimentary veneer over a passive basement to generate the arcs. The ultimate form of the fold bundles, however, may have been acquired in part through inheritance of initial curvature of the eastern margin of the miogeosyncline, and in part through rotation about vertical axes consequent upon differential transport. En echelon folding appears to be an integral part of the structural evolution of the region and a key to further understanding of the kinematics and dynamics of the Laramide orogeny in the northern Cordillera.