CHAPTER VI. 



STEATIGEAPHT OP THE DISTEICT. 



Palaeozoic formations. — The SMnilnunp. — Its strong lithological characters. — Constancy over wide 

 extent of country. — Coloring.— Architectural forms. — Age of the Shindrump, either Permian or 

 Lower Triassic. — Continuity with Red-beds of Colorado, New Mexico, and Arizona. — Triassic forma- 

 tion. — Vermilion CliflEs. — Cliff forms of the Triassic. — The Jurassic series. — Comparison of sec- 

 tions. — ^White sandstone. — Remarkable cross-bedding. — White Cliifs. — Architecture. — Jurassic 

 shales. — The Cretaceous. — Alternations of sandstone and iron-gray shales. — Dakota Group. — 

 Laramie Group. — Intervening formations not correlated. — Liguitic character of the Cretaceous. — 

 Close of the Laramie period. — Unconformities. — Post-Cretaceous disturbances and erosion, — Ter- 

 tiary formations. — ^Attenuation southward. — Pink Cliffs. — 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 elabora- 

 tion. Mr. Howell rapidly traversed the district in 1874 and seized the 

 salient features with remarkable rapidity and acumen. The geological hori- 

 zons 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. 



PALEOZOIC FORMATIONS. 



The oldest strata of the district belong to the closing epochs of Palaeo- 

 zoic 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- 

 kdgunt Plateau. The western side and summit of the Pdvant Range is 



143 



