Abstract

The East Kaibab monocline, a compound flexure downthrown 2000 to 5000 feet on the east side, extends from the San Francisco Peaks volcanic field, Arizona, north 150 miles to Bryce Canyon, Utah. South of the Grand Canyon the monocline has several branches which make abrupt changes of strike. The main flexure west of Cameron trends east, while other segments strike northwest, north, and northeast. With many small grabens, single faults, and rows of cinder cones the flexures form a structural pattern of three intersecting trends.

The main monocline, paralleled by the Butte fault, runs north across the eastern end of the Grand Canyon. A minor branch, paralleled by the Cremation fault, runs northwest into the Grand Canyon from Grandview Point. The Colorado River follows the strike of these major structures and may have had a subsequent origin in a belt of weak Triassic strata swinging south around the plunging Kaibab arch. The Little Colorado may have developed later in a similar belt at the foot of the East Kaibab monocline.

North of the Grand Canyon the monocline forms the eastern Kaibab Plateau margin and for part of this distance is a double or triple flexure. In Utah the monocline is a single great fold in Jurassic and Cretaceous strata. At Canaan Peak the Eocene Wasatch formation unconformably overlies beveled Upper Cretaceous strata in the monocline, indicating Laramide flexing.

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