118 GEOLOGICAL SURVEY OF THE TEREITOKIES. 



eastward of the present divide. One of the layers containing the best fos- 

 sils showed a plane of cleavage that was oblique to the plane of deposit, 

 rendering it extremely difficult to get perfect specimens. The color of 

 these sandstones was mosjily a gray, passing in places into a greenish tint. 

 Intercalated with them were some beds of basalt, which was probably 

 the cause of the metamorphism observed. In climbing over these hills 

 I found numerous indicatious of coal-beds, one of which was just above 

 our camp. There was no outcrop visible, but a prairie-dog in burrowing 

 had penetrated the bed, and revealed its presence by the coal he had dug 

 out. On the 21st 1 visited the hills west of camp. The first ridge was 41G 

 feet above the level of the creek, and composed of gray and green sand- 

 stones contain ing Inoceramus and other Cretaceous fossils. The dip of 

 these strata is 50° northeast ; angle of, inclination, 65°. The layers be- 

 tween this ridge and the Eocene on the opposite side of the valley, having 

 been soft sandstones, have been washed away to form the bed of the 

 stream. From this first ridge I ascended to the next, still higher, but 

 parallel to the first. The first strata were light-gray sandstones, very 

 much metamorphosed. These beds, which I take to be of Cretaceous 

 age, continued for about half a mile, and were followed by 50 feet of 

 coarse, reddish sandstones, the lower layers of which were conglomerate. 

 Next came a layer of very hard sandstone containing fragments of 

 fossils. This was about 10 feet in thickness, and is followed by 30 feet 

 of white quartzite. The summit of this ridge is 818 feet above the 

 valley and 402 feet above the top of the first ridge. I followed it until 

 the timber obstructed my passage, and I returned to the valley. These 

 beds are a continuation of those exposed at Spring Carion, and are 

 underlaid by the Jurassic and Carboniferous. Our course on the 21st 

 was up the valley to its head, when we crossed the divide to Trail Creek, 

 a tributary of the Yellowstone Eiver, which we followed and camped in 

 the valley of the Yellowstone. This divide is 5,821 feet above the sea. 

 The strata here have been so leveled and covered with debris and vege- 

 tation that it becomes very difficult to trace the various beds. It is 

 probable, however, that they curve toward the east and cross the valley,, 

 for a few miles after leaving the divide there is on the left-hand side of 

 the road an exposure of Carboniferous limestones dipping a little east 

 of north. On the right hand, a few miles to the south and west, there 

 are numerous volcanic peaks, their sharp, jagged edges standing out 

 boldly against the sky. As we neared the valley of the Yellowstone, 

 we came to a bed of volcanic breccia, resembling that at Mystic Lake 

 and originating evidently in the same center of eruption. Trail Creek 

 has cut through this breccia, leaving a high butte standing on the left 

 bank of the creek a few miles from its mouth. The top of this butte 

 seems to be composed of compact rock. A few miles from the divide 

 on Trail Creek there are coal-beds, none of which, however, have ever 

 been mined. 



Camp No. 3 was in the Yellowstone Valley, on Eight-Mile Creek, a 

 few miles from its junction with the river. The valley of the Yellow- 

 stone is filled with Pliocene deposits of about 150 feet thickness, on top 

 of which there are horizontal beds of basalt, which once probably ex- 

 tended over the whole valley, forming an immense i^lateau through 

 which the river has cut its bed, removing immense quantities of ma- 

 terial. The basalt is covered with local drift from the mountains. The 

 foot-hills on the western side of the valley are composed of volcanic 

 breccia. The^e has evidently been more than one period of eruption, 

 for farther uj) the valley there are several layers of basalt, between 



