Abstract

The formations used in dating the stages of deformation of the north-central Wasatch are the Twin Creek, Entrada (?), and Curtis (?) (Jurassic); the Kelvin (?), Aspen, and Frontier (Cretaceous); the Henefer (new name: lower Paleocene or uppermost Montana); the Wasatch group consisting of the Pulpit conglomerate (new name), Saw Mill conglomerate (new name), Fowkes (?) formation, and Knight (?) formation (middle Paleocene to middle Eocene); and the Norwood tuff (new name: lower Oligocene). Stages of deformation recognized are: (1) uplift and perhaps thrusting in a western highland at the beginning of Kelvin time, (2) thrusting in post-Frontier—pre-Henefer time (Taylor thrust), (3) renewed thrusting in pre-Henefer time (Ogden thrust), (4) crossfolding of thrust sheets and first major elevation of Uintas, also in pre-Henefer time, (5) renewed thrusting in post-Henefer—pre-Pulpit time (Willard thrust), (6) gentle crossfolding of Willard thrust sheet and folding of Pulpit conglomerate around Coalville anticline in pre-Saw Mill time, (7) renewed gentle folding prior to deposition of Norwood tuff, (8) gentle folding in post-lower Oligocene, erosion of Herd Mountain surface during the Miocene, (9) uplift, rejuvenation, and erosion of Weber Valley surface, a pediment, (10) Basin and Range faulting followed by dissection and alluviation of the pediment, the rise and fall of Lake Bonneville, and post-Bonneville dissection.

The structures trend in three directions, and problems concerning their superposition are discussed. The local structures are correlated with the regional from the standpoint of chronological development and of distribution and orientation. Tuffaceous beds indicate volcanic activity at five times in adjacent areas.

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