Abstract

LITHOPROBE seismic reflection profiles in the Kootenay arc of the southeastern Canadian Cordillera provide depth control on accretionary and postaccretionary structures. Detailed correlation of reflections to surface boundaries, including faults, folds, and stratigraphy,allows an unusually well constrained delineation of the present structure. Two related tectonic interpretations, differing only in the early development of the accretionary complex, include one in which layering conformable to the Early to Middle Jurassic obduction surface is tightly backfolded and an alternative in which backfolds are related to middle Paleozoic accretion(?). In both cases the accretionary complex is truncated at about 6 km by a listric detachment that placed it onto less deformed miogeoclinal strata. The steep tilt of the Kootenay arc is caused by its flanking position on an anticlinorium and by rotation(?) into a major normal fault.

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