Date of Award:
Master of Science (MS)
Clyde T. Hardy
The northern part of Clarkston Mountain, in northern Utah and southern Idaho, is located about 23 miles northwest of Logan, Utah. It extends across the Malad Range from Malad Valley on the west to Cache Valley on the east. The mapped area measures 4.8 miles in the north-south direction and 6.8 miles in the east-west direction.
The Brigham Formation of Cambrian age is the oldest exposed stratigraphic unit. It consists mainly of quartzite. Younger Cambrian units include the Langston, Ute, Blacksmith, Bloomington, Nounan, and St. Charles Formations. The Garden City Formation of Ordovician age is the youngest Paleozoic unit. The Salt Lake Formation of Tertiary age occupies the northeastern part of the area. It overlies Paleozoic units unconformably. The Lake Bonneville Group of Quaternary age is present both east and west of Clarkston Mountain.
Both thrust faults and normal faults are present in the mapped area. A bedding-plane thrust fault separates the Bloomington Formation from the overlying Nounan Formation. Two north-trending low-angle thrust faults involve Paleozoic rocks in the eastern part of the area. Eight north-trending low-angle normal faults cut the Paleozoic rocks of northern Clarkston Mountain and dip about 40° W. These formed as thrust faults; however, they are classified as normal faults because of reversed movement. Three north-trending high-angle normal faults also cut the Paleozoic rocks. A marginal normal fault, along which the area of Malad Valley has dropped relative to Clarkston Mountain, extends along the western side of the mountain. A marginal normal fault also extends along the southeastern side of Clarkston Mountain and continues northwestward over the Malad Range. The Salt Lake Formation, north of this fault, is down next to the Paleozoic rocks of Clarkston Mountain.
The thrust faulting with eastward movement is related to the Laramide orogeny, which occurred during the Cretaceous Period and the early part of the Tertiary Period. The bedding-plane thrust fault formed first. North-trending low-angle thrust faults formed later. Normal faulting, related to Basin and Range faulting, began early in the Tertiary Period and continues at the present time. Marginal normal faulting resulted in the great height of Clarkston Mountain relative to the major valleys on the west and on the east.
Burton, Steven Mark, "Structural Geology of the Northern Part of Clarkston Mountain, Malad Range, Utah-Idaho" (1973). All Graduate Theses and Dissertations. Paper 2115.
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