|
Page
16
|
Views
of Thrust Faults
*From west to east,
the primary thrust faults and times of movement of the Idaho-Wyoming thrust
belt are:
- Paris thrust (middle-Early Cretaceous 120-113 Ma)
- Meade thrust (late-Early Cretaceous 113-98 Ma)
- Crawford thrust (late Cretaceous 87-84 Ma)
- Absaroka thrust (late Cretaceous 84-74 Ma)
- Hogsback (Darby) thrust (Paleocene 63-57 Ma)
- Prospect thrust (Eocene 57-52 Ma)
(upper right) Crawford thrust fault, looking northwest at Cokeville Butte, north of Smith's Fork of the Bear River, near Cokeville, Wyoming, just east of the Idaho border. The conical hill is held up by upper Paleozoic Phosphoria and Wells Formations, folded into an anticline, the west limb of which is most prominent. The southwest-dipping Crawford thrust fault is immediately right (east) of the hill, in the gully below the left end of the left snow field. Below the Crawford thrust are Cretaceous rocks, (April,1984).
(right) Hogsback thrust fault, North LaBarge Creek, western Wyoming thrust belt. Thrust fault is at line of trees above the light cliffs. Light-colored Cretaceous rocks below the thrust form the front of the mountain. Cambrian Gros Ventre Formation (mainly shales) forms the slopes above the thrust at the top of the hill. Paleocene sandstones form the cliffs on top of the hill and provide a minimum age for movement on the thrust, (august,1977).
(bottom right) Willard thrust fault on the west face of the Wasatch Range south of Brigham City, Utah. Thrust fault lies in the trees above the light cliff (cambrian Tintic Quartzite). The Tintic lies nonconformably on Archean and Early Proterozoic Farmington Canyon Complex. Above the thrust fault is the Early Proterozoic Facer Creek Formation and the Late Proterozoic formation of Perry Canyon which contains evidence of Late Proterozoic glaciation, (July, 1982).
*Source: Armstrong and Oriel, 1965; Oriel and Armstrong, 1986
