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Steep crustal-scale faults, having their origins in the Late
Archean and Early Proterozoic and trending NE-SW, which define the
fundamental block lithospheric structure of the North American
craton, are seen from geological and geophysical evidence to
continue far into the interior of the Late Proterozoic-Phanerozoic
Canadian Cordilleran mobile megabelt. This suggests that variously
reworked ex-cratonic basement blocks underlie much of the
Cordillera. The western edge of the modern craton is probably near
the Rocky Mountain-Omineca belt boundary; the Rocky Mountain
fold-and-thrust belt on the east side of the Cordillera is
evidently rootless and overlies the undisturbed cratonic basement.
Phanerozoic differences between the Cordilleran tectonic belts,
resulting from a long, dissimilar, multi-cycle history of waxing
and waning orogenesis apparent from the rock record, lie chiefly in
the degree of indigenous tectonic remobilization and reworking of
the ancient crust.
Steep crystalline-basement faults, commonly indicated by
potential-field anomalies, played a crucial role in evolution of
continental cratonic platforms. In the Phanerozoic Western Canada
Sedimentary Province, history of crustal block movements and warps
is reconstructed from the distribution of depocenters, lithofacies
and structures in structural-formational etages in sedimentary
cover. Each etage is a rock succession formed during a particular
tectonic stage; regional tectonic restructuring closes each stage,
and the next stage represents a new tectonic regime. Practical
tectonic analysis, based on observation of rocks and geophysical
data, is a reliable guide for deciphering a region's geologic
history and for resource exploration."
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