Structural Geology of Cutler Dam Quadrangle and Northern Part of Honeyville Quadrangle, Utah

The mapped area is located in the north-central part of Utah. The northern part of the mapped area is located in the Basin and Range province and the southern part of the mapped area is located in the Middle Rocky Mountain province. The north-south and east-west dimensions of the mapped area are 11.1 miles and 5.1 miles, respectively. Paleozoic rocks are exposed in Bear River Narrows, in Cache Butte Divide, and in the Wellsville Mountains. Paleozoic strata, in Bear River Narrows, dip west. The Ordovician Swan Peak Formation crops out in the eastern part of Bear River Narrows. It is brown and white orthoquartzite. Westward, undifferentiated Fish Haven-Laketown Formation is exposed in Bear River Narrows and in Cache Butte Divide. The Fish Haven-Laketown is dolomite of Ordovician-Silurian age. The Devonian Water Canyon Formation is exposed west of Bear River Narrows and also on the western side of Cache Butte Divide. It is light-gray dolomite. A fault block of limestone of Mississippian Lodgepole Formation is present on the western side of the Wellsville Mountains northeast of Deweyville, Utah. The limestone is medium gray. The Pennsylvanian-Permian Oquirrh Formation is the uppermost Paleozoic unit in the mapped area. It consists of sandy limestone, blue-gray limestone, and calcareous sandstone. The Wasatch and Salt Lake Formations represent the Tertiary System. The Eocene Wasatch is a pebble and cobble conglomerate that is red. It rests on Paleozoic rocks in the northern part of the Wellsville Mountains and in the Bear River Narrows. The Salt Lake Formation is light-gray tuffaceous limestone, oolitic limestone, and conglomerate. It is exposed in Junction Hills, Cache Butte Divide, and in the northeastern part of the Wellsville Mountains. The age of the Salt Lake Formation, in the mapped area, is middle to late Pliocene. The Quaternary System is represented by colluvial deposits, Lake Bonneville Group, and alluvial deposits. The Pleistocene colluvial deposits consist of clasts of limestone and orthoquartzite set in an unconsolidated matrix. The Pleistocene Lake Bonneville Group crops out extensively in the mapped area. It is composed of gravel, sand, silt, and clay. The Holocene alluvial deposits include stream alluvium and alluvial fans. The Sevier orogeny and Basin and Range normal faulting affected northern Utah. The Sevier orogeny produced folds and thrust faults. The Basin and Range normal faulting followed and it is continuing at the present time. The Sevier orogeny, in the mapped area, is represented by a single thrust fault. A high-angle thrust fault, west of Chocolate Peak, placed Lodgepole Formation over the Oquirrh Formation. Reversed movement occurred during Basin and Range faulting. Thus, the fault is considered to be a normal fault. Basin and Range events include early and later normal faulting. Early normal faulting dropped the major valley blocks relative to the mountains. The Wasatch fault zone, on the western side of the Wellsville Mountains, and north-south marginal faults, on the eastern side of Junction Hills, formed at this time. Two faults, which diagonally transect the mapped area, form a northwest-southeast-trending graben. The northeastern fault extends along the western side of Cache Butte Divide and placed the Oquirrh Formation, in the graben, down relative to the Fish Haven-Laketown Formation of Cache Butte Divide. The southwestern fault cuts the northeastern part of the Wellsville Mountains and placed the Salt Lake Formation, on the northeast, next to the Oquirrh Formation. Later normal faulting cut the Lake Bonneville Group of Pleistocene age. Lake Bonneville Group is cut by a fault of the Wasatch fault zone as well as the fault that bounds the northeastern margin of the northwest-southeast-trending graben. Both faults placed the Lake Bonneville Group, on the west, next to the Salt Lake Formation