Regional Structural and Geophysical Studies of Interaction and Overlap
1988. "Regional Structural and Geophysical Studies of Interaction and Overlap", Interaction of the Rocky Mountain Foreland and the Cordilleran Thrust Belt, Christopher J. Schmidt, William J. Perry, Jr.
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Large Precambrian-cored thrust slabs dominate the west-central Montana thrust belt. Near Missoula, a western slab was emplaced over a thick eastern slab along an imbricate thrust zone in Campanian time, with development of a wide zone of cleavage in the footwall. Plunge projections suggest that the eastern slab is more than 25 km thick, with biotite zone rocks at depth and unmetamorphosed, syntectonic clastic deposits on top. It was thrust about 65 km to the northeast, forming a major anticlinorium above a large footwall ramp and an imbricate thrust fan in the Montana disturbed belt during Paleocene time. The slabs are comparable in dimensions to other cratonal margin thrust plates and to some uplifts of the neighboring Rocky Mountain foreland province.