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That the East Kaibab Monocline is an "old" geologic structure, is illustrated by the strata which were affected, and, most importantly, those not affected by the folding action. At the northern-most occurrence of the East Kaibab Monocline near Canaan Peak (just east of Bryce Canyon, Utah), inclined strata within the East Kaibab Monocline are beveled and overlain by the flat-lying Wasatch Formation.[3] We note immediately that the Wasatch Formation was not folded. The structural association indicates that the fold was produced after the last inclined stratum was deposited, but before the flat-lying Wasatch was deposited. Geologists refer to the uppermost inclined and beveled strata in the monocline as belonging to the Upper Cretaceous System. The unfolded Wasatch Formation, burying the monocline, has been assigned to the Eocene Series of the Tertiary System. [4] Geologists call this interval of deformation on the Colorado Plateau from the Upper Cretaceous to the Eocene the "Laramide Orogeny." This interval of uplift preceded the extensive erosion of the Colorado Plateau, because the Wasatch Formation is itself severely eroded as in the spectacular exposures at Bryce Canyon. We do not need to go to Utah to find evidence that the Kaibab Upwarp in northern Arizona is an "old" geologic structure. Gravel deposits occur within channels eroded into the surface of the Coconino and Kaibab Plateaus. These have been called "rim gravels," and have been the topic of intense study for twenty years. A major portion of the gravels have been assigned to the Paleocene and Eocene Series. [5] This means that the major uplift of the Coconino and Kaibab Plateaus was accompanied by the initial erosion of its surface during the Paleocene and Eocene—the time of the Laramide Orogeny on the Colorado Plateau. [6] These rim gravels, no doubt, provide the strongest evidence for the Laramide age of the Kaibab Upwarp. Therefore, the geologic relationships between the fold structure, the strata, and the erosion make the uplift of the Colorado Plateau look "old." We can discard the hypothesis that the Kaibab Upwarp was uplifted after the major erosion occurred. The major uplift must have occurred before erosion. Exactly how old is "old," is a point of debate between creationists and evolutionists. Conventional uniformitarian dating of the Upper Cretaceous is about 70 million years, and of the Eocene, is about 50 million years. The Laramide flexing of the Plateau is, thus, supposed to have occurred between about 50 and 70 million years ago. Almost every introductory geology text teaches both these great ages and their assignment to the Laramide Orogeny. Creationists, however, dispute the age assignment, but accept the observation that the monocline is deeply buried beneath strata of the Wasatch Formation. 4. Ibid. Recently, W. E. Bowers ("The Canaan Peak, Pine Hollow and Wastch Formations in the Table Cliff Region, Garfield County, Utah" U.S. Geological Survey Bulletin 1331-B[1972]:1 - 39) challenged the stratigraphic relationships at Canaan Peak. He suggested that the surface, called an unconformity at Canaan Peak is, instead, a fault surface. If the case for unconformity is weak, the the rim-gravel evidence should be used to evaluate the age of the Kaibab Upwarp. Return to Text 5. D. P. Elston, R. A. Young, E. H. McKee, and M. L. Dennis, "Paleontology, Clast Ages, and Paleomagnetism of Upper Paleocene and Eocene Gravel and Limestone Deposits, Colorado Plateau and Transition Zone, Northern and Central Arizona," in D. P. Elston, G. H. Billingsley, and R. A. Young, eds., Geology of Grand Canyon, Northern Arizona (with Colorado River Guidues) (Washington, American Geophysical Union, 1989), pp. 155 - 173. Return to Text 6. Ibid. Return to Text
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