Date of Award:
Master of Science (MS)
Robert Q. Oaks, Jr.
The Bear River Range, in north-central Utah, contains a variety of geomorphic elements influenced by the geologic setting and events. Controlling factors of the geologic setting include: (1) a syncline (west) and an anticline with a crestal graben (east) within the part of the mountain range studied, and an adjacent graben valley along the west side of the range; and (2) bedrock of Precambrian and Paleozoic age in the core of the range, predominantly of shallow-marine carbonates and covered in the graben by shaly and conglomeratic rocks of early Cenozoic age, with fanglomerates and lake deposits of later Cenozoic age. Geologic events contributing to geomorphic development include: (1) (?) Bull Lake and Pinedale glaciation; ( 2) various levels of Lake Bonneville; and (3) Hypsithermal climatic conditions.
The eighteen canyons along the western front of the Bear River Range in Utah, in sequence from north to south, are: High Creek, Oxkiller Hollow, Cherry Creek, City Creek, Nebo Creek, Smithfield, Birch, Dry (North), Hyde Park, Green, Logan, Dry (South), Providence, Millville, Blacksmith Fork, Hyrum, Paradise Dry, and East. An attempt was made to relate gradient changes along longitudinal canyon profiles to lithologies, attitudes, or other structural controls. The only consistent gradient change is a steepening of the gradient downstream from outcrops of Swan Peak Formation. A pronounced asymmetry in cross-valley profiles probably results from micro-climatic differences that cause north-facing slopes to be steeper than southfacing slopes despite close similarities in structure and lithology across canyons. Several canyons which do not cross the syncline axis have no measurable discharge. Water from these drainages apparently moves along the strike or down the east-dipping rocks of the western limb of the Logan Peak syncline to emerge as springs added to the surface flow in cross-axial canyon streams. Leakage is probably concentrated in the Lodgepole and Great Blue Formations.
Minor geomorphic elements within the Bear River Range result from glacial, periglacial, and fluvial processes, and landslides. Periglacial action has produced both nivation and patterned diamicton.
Glacial features are present in Logan Canyon and its tributaries, Birch, Providence, and the South Fork of Smithfield canyons. In addition to these previously mapped glacial areas, High Creek Canyon was subjected to glacial modification in the upper reach of South Fork tributary, and Leatham Hollow (Blacksmith Fork Canyon ), in the upper reach of its major southern tributary.
Nivation modified the heads of Smithfield, Green, Cottonwood, and Dry (South) canyons by carving cirques floored by rock debris. Evidence for glacial action downstream from these cirques is absent.
Patterned diamicton sites are widely distributed within the range. There is no consistent relationship to exposed lithologies or physical setting. The apparent relationship of slope aspect, elevation, and solar radiation suggests an origin by a temperature-dependent process, for near-identical temperatures were calculated for all patterned diamicton sites. Based, in part, on a reconstruction of Pleistocene temperatures, the patterned diamicton sites probably are a form of patterned ground resulting from frost action during glacial episodes.
Alluvial fans lie at the mouths of many tributary canyons. Based on degree of soil development and relations to features of known age, a sequence of fan development is recognized. Alluvial fans formed prior to Wisconsinan time and repeatedly thereafter during interglacial and glacial periods. Many of the fans formed after the Pleistocene under the favorable conditions that existed during the Hypsithermal interval.
Landslides in the study area are commonly old, inactive features. Only a few sites are recent in age, or currently active. Slopes with a west-component aspect are more prone to movement than other aspects. The most frequently disturbed lithology consists of Tertiary formations which are often conglomeratic. A wide range of slope inclinations have landslides, but the dominant slope is 20 to 24 percent. The main elevation range for landslides is between 6, 000 to 6, 999 feet.
Quaternary stream alluvium and Lake Bonneville deposits are found along the eastern margin of Cache Valley and in the lower reaches of most canyons. This material has been deposited since the Provo phase of Lake Bonneville. In several places, lake or stream terraces are mapped.
DeGraff, Jerome Vernon, "Quaternary Geomorphic Features of the Bear River Range, North-Central Utah" (1976). All Graduate Theses and Dissertations. 6658.