Date of Award:
Master of Science (MS)
Clyde T. Hardy
Seven Cambrian formations and two Ordovician formations, with a total thickness of 9,000 feet, crop out west of the Paris thrust fault and comprise the upper plate. Slices of three Ordovician formations, one Silurian formation, two Mississippian formations, and one formation each of Pennsylvanian and Permian age comprise the low plate. Mesozoic units are not present in the mapped area. Two Tertiary formations and unconsolidated Quaternary deposits are also present.
The major structural feature is the Paris thrust fault which extends north-south throughout the area. It was active during the Laramide orogeny. This fault involved eastward movement and placed Cambrian over Ordovician and later Paleozoic strata. The oldest formation exposed in the upper plate is the Brigham Formation which generally rests on the Garden City Formation. All units of the lower plate have been severely distorted and displaced by folding, thrusting, and reverse faulting. Both horizontal compression and gravity sliding have been invoked to explain this deformation. Gravity sliding is favored by many geologists; however, an uplifted source area has not been identified. Later, gravity faulting produced the major topographic features of the area today, notably the Bear River Range and Bear Lake Valley. (76 pages)
Davis, Clinton L., "Structural Geology of Southeastern Margin of Bear River Range, Idaho" (1969). All Graduate Theses and Dissertations. Paper 1443.
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