362 DYNAMICAL GEOLOGY. 



and Archaean No. 4 ; and then the Subcarboniferous limestone (Cb^) bends 

 over the summit, saddle-like, with some outcropping Devonian along the 

 middle. It is a complex system of zigzags in the great 30,000-foot pile of 

 rock formations. From the range of strata involved, and their thickness, it 

 is apparent that the making of the mountain was preceded by an accumula- 

 tion of strata from the top of the Cretaceous down to the Archaean; and 

 that the strata were slowly formed in a subsiding area, or geosyncline, like 

 the strata of the Appalachians. 



The relation of the Wasatch to the Uinta Mountains is learned by following the out- 

 cropping belts from near Weber southeastward to Echo, and thence to the Uinta. The 

 whole series of beds, from the Cambrian to the uppermost Cretaceous (the Laramie, Cr*, 

 finely cross-lined), is here included. The dips are eastward 45° or more to Echo, which 

 has Cr* either side, where they are 20°, and then northwestward to the top of the Uinta ; 

 there is hence a syncline at Echo, and an anticline at the broad Uinta summit, where the 

 dip is 4° to 5° north and south ; the rock, Cb'^, is the middle Carboniferous. 



Over the neck between the Uinta plateau and the Wasatch Eange, there 

 is a large area of igneous rock (trachyte) lettered /(the initial of fire, or the 

 Latin focus), apparently a consequence of the enormous amount of warping 

 in the great pile of rocks. Two other smaller trachytic areas exist to the 

 north in the same line. The Wasatch and Uinta regions were, therefore, 

 involved in a common system of profound movements, in which were flex- 

 ures and warpings, with fractures deep enough to let out melted rock. 

 Moreover, the country east of the Wasatch participated in the warp- 

 ing; for the Cretaceous beds occurring over it have high dips, and are 

 portions of flexures, or of upturned masses, that have become isolated by the 

 large amount of denudation which the country has undergone, the excava- 

 tions being not now visible only because they became filled by the depo- 

 sitions of the Eocene Tertiary. The Uinta plateau, on the landward side of 

 the Wasatch, has some relation in position to the Cumberland Table-land on 

 the landward side of the Appalachians. The great Uinta mass, 20 by 150 

 miles in area, is divided by deep fractures into a few blocks which are only 

 slightly displaced, as well illustrated by Powell. Seventy-five miles south 

 of Great Salt Lake, where the Wasatch Mountains proper may be said to 

 end, there commences the series of "high plateaus," which extends south- 

 ward to the borders of the Colorado Canon. This plateau region is one of 

 great faults, of few gentle flexures, and of monoclinal uplifts, with intersect- 

 ing canons as a result of its denudation. The rocks are the same that make 

 the Wasatch and Uinta Mountains, except that large areas are covered with 

 igneous outflows. 



The following cut (Fig. 336), by Powell, represents a portion of the plateau 

 region north of the Colorado Canon, with its flexures sometimes passing into 

 faults. The Colorado River flows in Marble Canon. The heights look 

 small, but the fault at W. K., the West Kaibab fault, is 2000 feet high ; at 

 E. K., the East Kaibab, 3000 feet ; at T., the Toroweap fault, 700 feet ; at 



