EASTERN FOOT-HILLS. 43 



Some of the richer carbonaceous shales along the Laramie Hills have been 

 examined for coal, but without success. The upper beds are somewhat 

 lighter in color, usually harder, and perhaps more siliceous. 



Only at one locality north of the railroad, about 2 or 3 miles north of 

 Horse Creek, do the Fox Hill beds, overlying the Fort Pierre, occur, and 

 even these may prove to be the extreme upper members of the lower division ; 

 everywhere else the Pliocene Tertiary strata conceal the beds above the 

 black clays. In Colorado, however, the Fox Hill beds extend along the 

 base of the range, and the junction between the Fort Pierre and the next 

 series above may be well seen. Here the more prominent clay-beds pass 

 into coarse argillaceous sandstone, of a dirty brown color and crumbling 

 texture, but carrying well-defined fossils, characteristic of the group. 



The Colorado beds, like all the other sedimentary strata along the base 

 of the range, vary somewhat in thickness, and appear to reach their greatest 

 development in Colorado. No accurate measurement of their thickness was 

 made at any one place, and it would be somewhat difficult to do so, as the 

 group is more or less covered with soil, and the dip extremely variable. 

 The lower members of the Fort Benton beds incline uniformly with those 

 of the Dakota ; but, owing to their plastic, flexible nature, are likely to fall 

 away to the eastward with a lower angle, which is not recognized until we 

 find the more prominent marls of the Niobrara lying inclined at a reduced 

 dip. The Fort Pierre clays would seem either still more flexible, or else, 

 removed farther from the main range, to have undergone less pressure in the 

 uplift of the strata, for we find the beds extending far to the eastward, flat- 

 tening out with low angles, frequently inclined at from 3° to 5°. In this 

 way, they change from an abrupt angle of 30° to nearly horizontal strata, 

 rendering an estimate of their thickness a matter of some difficulty. 



Their thickness may be best obtained by measuring at different points, 

 where well exposed, the several members of the group, and from these esti- 

 mating the entire expansion^ Probably the extreme development of the 

 Colorado beds will be found not to fall much short of 1,000 feet in Colo- 

 rado ; while, in Wyoming, the thickness will be somewhat less, but over 

 the greater part of the area the upper members of the series are never seen. 



