The Precambrian Farmington Canyon complex crops out in the Wasatch Mountains between Ogden and Bountiful, Utah. Additional exposures are present at Durst Mountain and at Antelope Island.

East of Ogden, between Ogden Canyon and Strongs Canyon, the Farmington Canyon complex has been thrust eastward over Lower Cambrian Tintic Quartzite and Middle Cambrian shales and limestones of the Ophir Formation and Maxfield Limestone. This thrust is named the Ogden thrust. Similarly, at Durst Mountain, east of Morgan Valley, the Farmington Canyon complex has been thrust over Lower Cambrian Tintic Quartzite and Middle Cambrian shales and limestones. This thrust fault is the Durst Mountain thrust. If subsequent vertical offset of 2,000-4,000 ft (610-1,220 m) down to the west on the Morgan Valley normal fault is restored, it appears that the two similar thrusts involving the Farmington Canyon complex could once have been continuous. Such a reconstruction requires a minimum of 12 mi (19 3 km) of thrust displacement of the complex eastward over the sequence of basal Cambrian rocks.

This evidence is significant for two reasons: (1) the Farmington Canyon complex of the Wasatch Mountains may not be in place, but may be allochthonous above a decollement at depth; and (2) the Paleozoic-Mesozoic sequence east of Morgan may also overlie the same decollement, which would increase the potential for petroleum plays in the area north of Croyden.

Thus, the northern Utah uplift, proposed for this area by A. J. Eardley and discussed by M. D. Crittenden, may result from a sequence of Farmington Canyon complex thrust upsection eastward, rather than a vertical uplift of basement.

End_of_Article - Last_Page 948------------