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Show CHAPTER VI. STEATIGRAPHY OF THE DISTEIOT. Palaeozoic formations.â€"The ShinaYump.â€"Its strong lithological characters.â€"Constancy over wide extent of country.â€"Coloring.â€"Architectural forms.â€"Age of the Shina^rump, either Permian or Lower Triassic.â€"Continuity with Eed-beds of Colorado, New Mexico, and Arizona.â€"Triassic formation.â€"Vermilion Cliffs.â€"Cliff forms of the Triassic.â€"The Jurassic series.â€"Comparison of sections.â€"White sandstone.â€"Remarkable cross-bedding.â€"White Cliffs.â€"Architecture.â€"Jurassic shales.â€"The Cretaceous.â€"Alternations of sandstone and iron-gray shales.â€"Dakota Group.â€" Laramie Croup.â€"Intervening formations not correlated.â€"Lignitic character of the Cretaceous.â€" Close of the Laramie period.â€"Unconformities.â€"Post-Cretaceous disturbances and erosion.â€"Tertiary formations.â€"Attenuation southward.â€"Pink Cliffs.â€"Tertiary lignites. The study of the stratigraphy of the District of the High Plateaus and of the regions adjacent thereto has been chiefly the work of Messrs. Powell, Howell, and Gilbert. I have had little to do with it, except to take their results as starting points and add my own testimony in the way of elaboration. Mr. Howell rapidly traversed the district in 1874 and seized the salient features with remarkable rapidity and acumen. The geological horizons of the larger groups were determined by him, and all that was left to me was to ascertain their extent and distribution in greater detail. PALAEOZOIC FORMATIONS. The oldest strata of the district belong to the closing epochs of Palaeozoic time; except, however, that upon the northwestern flank of the Tushar some crystalline rocks, supposed to be of Archsean age, are revealed in momentary exposures in the ravines where the overmantling rhyolite has been deeply scored by the mountain streams. On the northeastern flank of the Aquarius Plateau the summit of the Carboniferous is laid bare, the exposed area being about eighteen miles in length by six miles in width at the widest part. A remarkable dislocation, forming a part of the Hurricane fault, turns up a brief exposure of the same horizons southwest of the Mar-kagunt Plateau. The western side and summit of the Pavant Range is 143 |
