14 REPOET UNITED STATES GEOLOGICAL SURVEY. 



Feet. 



7. Pretty firm sandstone, with occasional pockets of lignite and carbonaceous 



clay. Some obscure impressions of leaves and shells 160 



8. Sandstone, alternating with sand shales, lignitic seams, and clays. First prom- 



inent outcrop in ascending from the river 300 



9. Gray, dark gray, and blackish sandy shales, in places much indurated, and, 



where in contact with intruded basalts, quartzitic. These form the lower part 

 of the wall and reach to the river bed. They are much obscured by cUbris, 

 These strata all dip at angles varying from 8° to 15° to the north or north- 

 northeast - 900 



In the sbales beneath the intruded mass of basalt, shown in Plate 

 VII, there are namerous but rather obscure impressions offish scales. 



The lignites which occur so plentifully in the strata of this mountain 

 are generally of a very inferior quality, and if we are to judge from the 

 surface indications will probably never be available for economic pur- 

 poses. 



Along the banks of the Gardiner, below the junction of the East Fork, 

 there are outcrops of Cretaceous shales that indicate some local dis- 

 turbance by which they have been tipped up at pretty high angles. 

 These disturbances are probably owing to the intrusion of masses of 

 basalt rather than to any general movement. 



Mount Evarts is separated from the high plateau region south of 

 the forks of Gardiner Eiver by the deep valley of the East Fork. The 

 strata, however, are continuous, and will be found to correspond on 

 the opposite sides of the valley. On the south side they are much 

 obscured by the loose debris of land slides, and soon disappear entirely 

 beneath the broad sheets of rhyolite that form the surface of the south- 

 ern plateaus. The basaltic intrusions are very numerous, and at the 

 falls of the East Fork heavy masses of dark columnar basalt occur. 

 The sheet of rhyolite overlies these basalts at the falls and is weathered 

 back from the brink of the cliffs at the north. The flat region that extends 

 from the Ea.st Fork above the falls eastward toward Junction Valley, 

 as well as the greater part of the flat summit of Mount Evarts, is cov- 

 ered with coarse drift which consists greatly of granitic material. 



Between the front ridge of Mount Evarts and the group of hills — men- 

 tiimed in describing the Yellowstone displacement — which form the ex- 

 treme northeastern portion of the mountain, we have a gently undula- 

 ting country which possesses much pastoral beauty. Groves of pines 

 and aspens'dot the broad expanse of rich grass land, and numerous 

 ponds and lakes occupy the depressions between the low hills and ridges. 



I found two of the higher summits of the group of hills just men- 

 tioned capped with rhyolite, similar in every respect to that which 

 forms the broad summit of the main mountain. Beneath this rhyolite 

 on the northern side of the hills are some slight outcrops of horizontal 

 strata that apparently belong to the later Tertiary. On a subordinate 

 butte to the north these strata contain a number of stumps of silicifled 

 trees, which rise through the inclosing sandstones and conglomerates, 

 and stand a few feet in height. There are also some basaltic layers in 

 these strata. Beneath on all sides are the stratified schists. The river 

 runs in a deep, narrow caiaon in these rocks, upwards of 2,000 feet below 

 the summit of the hills. North of the river the rugged slopes are com- 

 posed entirely of the schistose rocks. The strike of these rocks is north 

 some 40° or 50° E., and the dip always to the southeast at a high angle. 



In descending to the valley of Black-tail-deer Creek, I passed down 

 over the schistose strata and on the opposite side soon reached a region 

 covered with basalts. The valley of Black-tail-deer Creek has but 

 slight exposures of strata. A heavy sheet of drift, probably both river 



