Excerpt from Colorado Plateau Region Except for the Archean and Algonkian formations at the bottom of the Grand Canyon the Colorado Plateau province is essentially a region of sedimentary rocks - a pile of Paleozoic, Mesozoic, and Tertiary strata, chiefly sandstone, more than 10 000 feet (3, 050 meters) thick and exposed over an area exceed ing square miles (388, 500 square kilometers). The sedimentary beds of the region are representatives of broadly defined stratigraphic groups that extend northward in Utah to the ...
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Excerpt from Colorado Plateau Region Except for the Archean and Algonkian formations at the bottom of the Grand Canyon the Colorado Plateau province is essentially a region of sedimentary rocks - a pile of Paleozoic, Mesozoic, and Tertiary strata, chiefly sandstone, more than 10 000 feet (3, 050 meters) thick and exposed over an area exceed ing square miles (388, 500 square kilometers). The sedimentary beds of the region are representatives of broadly defined stratigraphic groups that extend northward in Utah to the Uinta (you-in' tah) Mountains, eastward into Colorado and New Mexico, southward to central Arizona, and westward beyond the utah-nevada boundary line. Like the Permian (kaibab) limestone that now constitutes the surface rock on both sides of the Grand Canyon, beds of Triassic, Jurassic, and Tertiary age, similar to those exposed in the cliffs of the High Plateaus and in buttes and mesas in northern Arizona, are believed to have been once continuous across the Colorado, providing a cover twice as thick as the present canyon is deep. The stratigraphic section exposed reveals evidence of extended intervals of earth movements and erosion. In the walls of the Grand Canyon the Algonkian beds rest on the eroded surface of a mountain range and are unconformably overlain by the Cambrian; the Ordovician and Silurian are lacking, the Devonian is present in patches only, and ancient surfaces of erosion are represented by unconformities at the base of the Redwall (mississippian) and the base and top of the Supai (permian). In the rocks that form the plateaus north and south of the Colorado there are unconformities of regional significance be tween the Kaibab (permian) and the Moenkopi (mo-en ko 'pi) (triassic), between the Moenkopi and the Shinarump (shin air 'ump) (triassic), and between the Cretaceous and the Tertiary, besides breaks that indicate shorter lapses between other formations. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at ... This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.
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