Date of Award:
Master of Science (MS)
Clyde T. Hardy
The mapped area represents the eastern three-fourths of the Smithfield quadrangle, Utah. This quadrangle is located in the central part of northern Utah about 8.6 miles south of the Utah- Idaho State Line. The Bear River Range, along the eastern margin of the quadrangle, consists of stratigraphic units ranging in age from Precambrian to Devonian. The Salt Lake Formation of Tertiary age rests unconformably on Precambrian quartzite and Paleozoic units along the western side of the range. The Lake Bonneville Group overlaps Cambrian rocks in the southern part of the area and overlaps the Salt Lake Formation in the northern part.
The Paleozoic rocks of the mapped area dip generally east on the western limb of the Logan Peak syncline. The east-dipping beds of the western limb, along the mountain front, are broken by east-dipping bedding-plane faults and by west-dipping high-angle and low-angle thrust faults. A prominent west-dipping surface probably formed as a thrust fault; however, later westward sliding took place on this surface. The bedding-plane faults are interpreted to have formed by: eastward sliding of the mountain mass. Progressive local deformation, on the western limb of the Logan Peak syncline, produced high-angle and low-angle thrust faults successively. The folding and thrust faulting are related to the Laramide orogeny and occurred during the Cretaceous Period and the early part of the Tertiary Period.
Numerous gravity faults extend along the western front of the Bear River Range. The relative collapse of Cache Valley, early in the Tertiary Period, produced great topographic relief. This resulted in slope instability and, as a consequence, large masses moved down the west-dipping surface and two major landslides occurred. The landslides seem to have moved over the lower member of the Salt Lake Formation and seem to have been covered by conglomerate of the upper member. Gravity faulting has continued to the present time.
Galloway, Cheryl Leora, "Structural Geology of Eastern Part of the Smithfield Quadrangle, Utah" (1970). All Graduate Theses and Dissertations. 2117.
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