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Cenozoic Extensional Processes And Tectonics In The Northern Rocky Mountains, Susanne U. Janecke
Cenozoic Extensional Processes And Tectonics In The Northern Rocky Mountains, Susanne U. Janecke
Susanne U. Janecke
Extension has shaped the crust of the Northern Rocky Mountains for more than a billion years. Rifting produced the Belt basin shortly after 1.5 Ga and initiated the Paleozoic passive margin. Mesozoic to early Cenozoic convergence pro-duced the Cordilleran fold-and-thrust belt, the uplifts of the Rocky Mountain foreland (Laramide) and an unusually broad Challis arc in the northern Rocky Mountains. The struc-tural grain of the contractional belts, basement features, and the rheology of the Idaho batho-lith influenced the locus, kinematics and ge-ometry of the >55 m.y. of extension that fol-lowed. Sparse data suggest that extension may have begun in the …