412 DESCRIPTIVE GEOLOGY. 



The .12 per cent, of phosphoric acid present would seem to be derived from 

 shells of the genus Oholella and other minute forms. The sandstones in 

 the Ute Peak beds occur mostly in thin layers, usually granular, and 

 carrying a considerable percentage of lime, and are found throughout 

 the entire series, while the shales and slates appear, for the most part, to 

 be confined to the lower horizons. As already mentioned, the argillaceous 

 and arenaceous slates, which have been referred to the upper members of 

 the Cambrian, occupy the cailon-bottom. They are estimated at about 100 

 feet in thickness, and consist of exceedingly fine indurated clay-beds, inter- 

 laminated with layers of sand material of a brown earthy color, closely 

 resembling the beds from the same horizon in Ogden Canon. On the north 

 side of the Muddy, no lateral canon has cut through the slates, and there 

 are found the Ute limestone and Cambrian quartzite forming a high canon- 

 wall, exposing a fine unbroken section, dipping about 16° to the westward. 

 The two forks of Muddy Canon ofi'er a striking difference in structural 

 features; the canon of the south fork trending approximately with the 

 strike of the rocks, and presenting on one side the high wall of the Ute 

 limestone and on the other the Cambrian quartzite, the intermediate slates 

 being almost entirely eroded off the steep slope. On the other hand, the 

 north fork, running at- right angles to the quartzite, cuts through 1,600 

 feet of the Cambrian rocks, forming a narrow impassable gorge, with pre- 

 cipitous and almost perpendicular walls. 



Cambrian Plateau. — The large area of quartzite which underlies the 

 Silurian limestone, and has been referred to the Cambrian series, occupies a 

 very large superficial area. It extends from the northern limit of the map 

 across Logan, Blacksmith's, and Muddy Canons, and as far south as Ogden 

 River, occupying a belt of country from 6 to 8 miles in width. It forms a 

 broad anticlinal fold, whose western side dips under the Ute limestone in 

 the region of Logan and Blacksmith's Canons, with a low angle, increasing, 

 however, toward the Muddy, where it reaches an inclination of 16°. The 

 Bear Lake road, as shown on the map, appears to lie along the axis of the 

 anticlinal fold, and here the quartzites are found quite horizontal, or else 

 dipping under the influence of the eastern side of the fold 2° or 3° to the 

 eastward. The eastern side of the fold is by no means as steep as the 



