HOLMES.] GEOLOGY OF MOUNT EVAETS. 13 



catalogue. It lias a tendency to weather in rude columns, but these are 

 not clearly deliued. It doubtless forms a part of the great rhyolitic 

 sheet, the borders of which can be found at a similar level all around the 

 rim of the yalley of Gardiner E-iver, and which appears elsewhere fur- 

 ther east. 



The edges of the sandstone strata which come in contact with the 

 white tufaceous stratum are somewhat discolored as if by metamorph- 

 ism or oxydization of minerals. The section of these strata as given 

 farther oti extends from this point directly down the face of the clifis, 

 reaching G-ardiner River at the base of the Mammoth Hot Springs. 



On the loth of August we had been forced by continued snow-storms 

 to relinquish work in the Gallatin Mountains, and arrived at the springs 

 preparatory to starting for Bozemau. On the 14th, accompanied by Dr. 

 Peale, who had just arrived from the Geyser Basin, I determined, not- 

 withstanding the fact that the snow was three or four inches deep, to 

 examine the strata in the great wall of Mount Evarts. 



Descending to the river, we passed over, as on a previous occasion, 

 extended bodies of hot-spring deposits, beneath which, near the river, a 

 limited outcrop of sandstones occnr. These sandstones probably belong- 

 to the Dakota Group of the Cretaceous, and consist of 20 to 30 feet in 

 thickness of massive, coarse-grained sandstones that dip beneath the 

 bed of the river at an angle of about 15<^. It is probable that these 

 sandstones underlie a greater part of the drift and sinter-covered slopes 

 of the west side of the valley. Beneath the massive bed of sandstone 

 some laminated beds appear, which doubtless belong also to the Creta- 

 ceous. 



Crossing the river, we rode for a considerable distance up the gorge- 

 cut talus slope, which is covered with grass and sage. We hitched our 

 animals, as far up as they could be taken, at the height of nearly 1,000 feet 

 above the river bed, just opposite a steep cliff which overhangs a deep 

 gulch. In the vertical part of the cliff are exposed about 200 feet of 

 light- gray argillaceous and sandy shales. 



From the base of the vertical cliff we climbed, not without consider- 

 able difficulty, as a snow-storm was raging, to the summit of the mount- 

 ain at the northern end of the rhyolite escarpment. Rather imperfect 

 impressions of leaves were found at a number of localities. Professor 

 Lesquereux having examined them, announces that they certainly indi- 

 cate Che Cretaceous age of the formation. A small number of rather 

 imperfect fossil shells were found near the top, which are considered by 

 Professor White to represent Upper Cretaceous, and possibly Post-Cre- 

 taceous species. 



The section, beginning at the top, is as follows : 



Feet. 



1. Driff^. 



2. Purplish sanidine trachyte 80 



3. Stratified tufaceous sandstones 8 



4. Sandstones, alternating with clay, sand, and carbonaceous shales. Near the 



upper part are some layers of flinty concretiouary limestone. Beneath these 

 and just under the ends of the rhyolite bed is a leaf-bearing stratum of sand- 

 sfcoue, containing the following species : Sequoia Eiclieiibachi, S. fasUqiata, S. 

 81'bulata, Andromeda Parlatori, Bonmctia Marconana, a proteoides and frag-- 

 nients of conifers. The sandstones contain many irregular and oval masses 

 of clayey and carbonaceous matter, and also musses of wood 60 



5. Sandstones, sand shales, clays, and lignitic clays. The softer strata predomi- 



nate. The beds of sandstone are seldom more than 4 fept thick. Near the 

 base of this group a number of the fallen fragments of sandstone were found, 

 in which were imbedded the following fossils, all of which are in a very poor 

 state of preservation : Corlmla (?), Vivipcrous (?), Goiiiabasiti (?), Oslrca {?)... 225 



6. Carbonaceous shales and lignites. Some of the seams of lignite are upwards 



of 10 feet iu thickness, but contain much lire clay and other imi)urities 40 



