26 THREE GEOLOGICAL PROVINCES. 



other mountains of this type are found m the Sevier district The Uinkaret 

 Mountains, which have been t :ken as a type of structure, are on the north 

 side of the Grand Canon of the Colorado. San Francisco Mountain and 

 other mountains in that vicinity are known to be of this structure, but this 

 great group of mountains, of which San Francisco Mountain is the culmi- 

 nating peak, has not been sufficiently studied to enable us to characterize 

 them. The Navajo Mountain, Sierra la Sal, and others in this region are 

 knoAvn to be of the Henry Mountain type. 



The principal number of important peaks and great mountain masses 

 of the Plateau Province are divided about equally between the last two 

 classes. Some mountains of the Tu-shar structure are found in the Sevier 

 district. Volcanic cones are found in great numbers throughout the south- 

 ern portion of the province. 



GEOGRAPHIC STRUCTURE OF THE PARK PROVINCE. 



The great mountain masses of the Park Province, especially those to 

 the north standing about the South, Middle, and North Parks, which I have 

 myself seen, are composed of metamorphic crystalline schists. It would 

 appear that these schists were metamorphosed antecedent to the deposition 

 of the Paleozoic, Mesozoic and Cenozoic rocks, which are found in many 

 places resting unconformably upon them ; for all these later sedimentary 

 beds contain to a greater or less extent conglomerates which are composed 

 of fragments of metamorphic materials resembling those of the principal 

 mountain masses ; and it further appears from my brief studies that this 

 series of rocks was profoundly plicated, perhaps on the Appalachian type, 

 i. e., with closely appressed folds, and this also prior to the deposition of the 

 upper sediments. Through Paleozoic and Mesozoic times minor changes of 

 level have occurred, now lifting the area above the sea, now submerging it, 

 so that many gentle unconformities are found with an interrupted succes- 

 sion of sedimentary beds. But the last great orographic displacements 

 are represented by broad upheavals which appear to have the structure of 

 the Uinta Mountains, so far as can be made out from the fragmentary 

 evidence left by the great erosion to which the country has been subjected 



