144 DESCRIPTIVE GEOLOGY. 



di#aiy plain of nearly horizontal sandstones. In an economical point of 

 view, it derives its sole interest from the heavy deposits of coal underlying 

 the town, which have been extensively mined for a number of years. Geo- 

 logically, the place has also received considerable attention in examining 

 the question as to the age of the Wyoming coals. There would appear to 

 be but little doubt that the beds belong to the Laramie division of the 

 Cretaceous sandstone. In determining the true horizon of these beds, how- 

 ever, it is necessary to trace out their relations with the great sandstone 

 formation, which forms all the higher ridges of the region, and to compare the 

 strata with other similar localities. The beds at Carbon occupy a broad, 

 irregularly-shaped basin, the rocks on the west, south, and east all dipping 

 .in toward the centre, surrounding it completely on three sides. Between one 

 and two miles west of Carbon, a high, prominent ridge of Fox Hill sandstones, 

 known as Simpson Ridge, whose highest point, just south of the railroad, 

 rises some 800 feet above the level of the town, shuts in the valley on that 

 side. South of the railroad, this ridge, which is quite regular in outline, 

 trends approximately north and south, but to the north falls away consider- 

 ably, curving around to the northeast. Its structure is that of a very per- 

 fect anticlinal fold, whose axis passes through the high point already men- 

 tioned. The beds upon the east side of the ridge facing Carbon dip at 55° 

 to 60°, while upon the opposite side of the fold the same rocks dip westward 

 at 35° to 40°. In the axis of the fold lies a brilliant pearl-gray, medium- 

 grained sandstone, which is overlaid on both sides by a series of arenaceous 

 and ferruginous clays, with the following subdivisions: 



1. Thinly-laminated arenaceous clay. 



2. Eusty sandstone, with ferruginous seams. 



3. Ferruginous fine-grained claystone, 4 feet. 



4. Fine black clay, 50 feet. 



5. Ferruginous claystone, 3 feet. 



6. Crumbling rusty sandstone. 



Overlying the latter are sandstones similar to those from the summit, 

 but perhaps not quite so white, which are in turn overlaid by coarse red 

 sandstones reaching to the base of the ridge. A marked peculiarity of 

 outline, seen upon both sides of the ridge, and one that adds a striking 

 feature to the anticlinal structure, is the similar shallow valleys formed, high 



