8 THUEE GEOLOGICAL PROVINCES. 



The Plateau Province is composed of many tables bounded by canon 

 and cliff escarpments. On these tables stand lone mountains, irregular 

 groups of mountains, and short ranges. It is drained by the Colorado 

 River of the West and its tributaries. 



The Park Province is characterized by broad, massive ranges, sometimes 

 distinct, sometimes coalescing so as to include the great parks. The lofty peaks 

 that serrate these ranges stand over snow banks that are perennial reservoirs 

 for a multitude of streams whose waters on one hanc). are gathered into the 

 Colorado River of the West, and finally discharged into the Gulf of Cali- 

 fornia ; and on the other hand they are gathered into the Mississippi and 

 the Rio Grande del Norte to be discharged into the Gulf of Mexico. 



Thus, in the three provinces, we have, first, desert valleys between 

 naked ridges ; second, high plateaus severed by profound gorges ; and, 

 third, massive, high mountains with shining snow fields. 



GENERAL CHARACTERISTICS OF THE SEDIMENTARY GROUPS 



OF THREE PROVINCES. 



The Basin ranges are composed of Paleozoic rocks with Eozoic schists 

 below, and in the Humboldt Mountain district some Mesozoic and Cenozoic 

 rocks are found. In the Plateau Province, Cenozoic and Mesozoic rocks 

 prevail, though some of the important plateaus are of Carboniferous beds ; 

 and in a few places deep corrasion has revealed still older Paleozoic and 

 even Eozoic formations. The Park Mountains are chiefly Eozoic Since 

 that age the region has been intermittently under the dominion of the 

 waters, and Paleozoic, Mesozoic, and Cenozoic rocks are found at horizons 

 interrupted ]>y gaps in the general series that are represented by dry land 

 periods, wl. : le the last orographic agencies have left but fragments of these 

 antecedent formations. 



