158 DESCRIPTIVE GEOLOGY. 



passes the road from the Little Muddy to Rawlings Station, seems to 

 occupy a slight synclinal depression, which in the middle may be merely 

 a slight faulting. 



In going northward from a point on the Little Muddy, about 5 miles 

 west of the Sulphur Springs, a thickness of between 3,000 and 4,000 feet 

 of beds of the Laramie group, dipping northwest at an angle of 20°, is 

 crossed. Of these, the lower 2,000 feet are composed of massive white and 

 yellow sandstones, in which the shale beds are of subordinate importance. 

 The upper sandstones are stained and striped in red by iron oxide, and form 

 ridges with considerable clayey valleys between. In the upper 800 feet 

 are several coal-seams, and near the top is a prominent bed of bright ver- 

 milion color, only a few feet in thickness, of fine-grained, hard, argillaceous 

 material, abounding in well-preserved impressions of leaves. This is over- 

 laid by a white sandstone about 200 feet in thickness, carrying a coal-seam, 

 which in turn is capped by a thin-bedded brown sandstone, which weathers 

 into flags about 3 inches in thickness ; the dip of these upper beds has 

 shallowed to 10°, and to the north the beds of the Laramie group are prac- 

 tically horizontal. 



The heavy white sandstones of the Fox Hill group, which form the 

 bluffs of the northern face of Bridger's Pass, bend in strike to the north- 

 ward, east of Separation Peak, shallowing in dip at the same time to almost 

 horizontal. On the east side of the low saddle, between Sage Creek Val- 

 ley and Eawlings, they form bluffs facing westward, standing here with a 

 dip of 10° to the east, or, in other words, this pass occupies a low anticlinal 

 fold, the southern extremity of the Rawlings Peak uplift. 



For eight miles to the west of Fort Steele all traces of the underlying 

 beds are lost beneath the soft clayey soil, characteristic of valleys which 

 are worn out of beds of the Colorado Cretaceous. Just south of the rail- 

 road, about midway between Rawlings and Fort Steele, is a double line of 

 low ridges, formed by thin-bedded sandstones and interlaminated clays, 

 which join at the east and open out to the west, representing the anticlinal 

 fold whose indications are seen near tEe latter point. Near the railroad 

 section-house, in the northern of these ridges, was found in sandstones 

 dipping 35° with a strike 5° north of west, a curious deposit of white 



