182 GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



which at its western end is superimposed upon the breccia. The north 

 slope of this ridge, forming the south wall along Wolverine Creek, consists 

 mainly of bedded sandstones and impure shales inclined to the southwest, 

 but, owing to the mantle of soil, both the dip and the strike are most 

 difficult to determine. 



The mountain slopes along the north side of Wolverine Creek present 

 a remarkable exposure of massively bedded yellow sandstone, with prevail- 

 ing dips to the south and southwest — that is, toward the valley. No fossils 

 have been obtained from these beds, but they have been assigned to the 

 Montana formation. Higher up the valley they pass by insensible grada- 

 tions into beds less regular in their sedimentation, carrying clays and 

 earthy material with interbedded ferruginous sandstones. The latter series 

 of beds, from their lithological habit, have been placed in the Laramie, but 

 without any sharp lines of demarcation between the two formations. They 

 lie conformably on the older beds to the north and west, and pass beneath 

 the valley, dipping into the ridge on the opposite side. Due north of Pin- 

 yon Peak, and rising as an abrupt wall on the south side of Wolverine 

 Creek, stands a somewhat prominent hill, several hundred feet in height. It 

 affords an excellent exposure across characteristic Laramie strata nearly 

 200 feet in thickness. These consist of yellowish-brown sandstones, with 

 interbedded blue and black clays, rusty sandstones, and thin carbonaceous 

 layers. 



Along the stream bed are exposed outcrops of five distinct, thin seams 

 of inujrare lignite with more or less fragmentary impressions of plant remains. 

 The beds strike northwest and southeast, and dip from 25° to 30° SW., 

 passing under the mass to Pinyon Peak. 



Higher up the valley at several localities the banks along the stream 

 expose arenaceous blue clays and black shales with evidence of carbona- 

 ceous material, and in places carrying well-preserved leaves. These beds 

 also dip to the southwest. Again, on the divide between Wolverine and 

 Gravel creeks, and due east of Pinyon Peak, similar beds of arenaceous 

 clays are exposed along the ravines and in the banks cut by numerous small 

 streams. These beds along the summit of the pass dip to the southwest and 

 west and are finally lost beneath the conglomerates of Pinyon Peak. The 

 divide between these two creeks, which lies at an elevation of 8,500 feet 

 above sea level, is cut entirely in the Laramie sandstones. 



