VII- Migration of the Foredeep
Plate 17 - The foredeep sequence developed in the Rocky Mountains during most of Mesozoic time. The clastic rocks were derived from Paleozoic and metamorphic rocks outcropping in highlands in central British Columbia. As deformation progressed, some of these clastic rocks were re-sedimented into new and younger foredeeps. The axis of the asymmetrical basins migrated eastward. The underlying basement of the Rocky Mountains kept subsiding during this period. The westward side of the younger foredeep unconformably onlaps its predecessor. Bally assumed that the Foothills were deformed during Eocene time, the Front Ranges followed deposition of the Upper Cretaceous, and that the Main Ranges were conceivably deformed much earlier, perhaps after deposition of the Lower Cretaceous.
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