Geological Survey Professional Paper 132—A Rock Formations in the Colorado Plateau of Southeastern Utah and Northern Arizona

TERTIARY SYSTEM.

In the High Plateaus are found exposures of the youngest stratified rocks of the region, comprising pink, lavender, white, and varicolored limestones, sandstones, and shales of Eocene age. These rocks, which in Garfield and Kane counties have been referred to the Wasatch formation, appear in vertical cliffs and in the fantastically carved, brilliantly tinted walls of canyons that head along the margins of the plateaus. The thickness of the Tertiary sequence in this region is about 2,000 feet. Much of it, especially toward the north, is buried beneath a great accumulation of extrusive igneous rocks.

The Tertiary beds rest with very great unconformity on the Mesozoic rocks, the unconformity being angular as well as erosional. The base of the Tertiary is found in contact successively with all the formations from the highest Cretaceous to the Navajo sandstone, and much of the Navajo was in places removed before Eocene sedimentation. It therefore appears that an important deformative movement; in which such structural features as the Waterpocket Fold, the Circle Cliffs dome, and the gentle flexures south of Table Cliff Plateau were formed, followed Cretaceous deposition, and that before the deposition of the Tertiary strata began this deformed rock series had been planed off by erosion to a nearly level surface, a denudation involving the removal in places of rock strata some thousands of feet in thickness.