HOLMES.] DISPLACEMENT, YELLOWSTONE VALLEY. 7 



volcanic conglomerates that form tlie bulk of Sepulchre Mountain seem 

 to form a continuous and unbroken series. 



From the mouth of Cache Creek to the mouth of Gardiner's Eiver the 

 Yellowstone Kiver remains in the synclinal fold which appears at e in 

 Section A, and at h in Section B. The line of the fault probably runs 

 nearly i)arallel to this fold, but is from one to two miles to the north. 

 Between the river and the fault-line is a broad, irregular bench which 

 has a general elevation of 200 or 300 feet above the river. Outcrops of 

 shales and sandstones, the former gray and the latter yellow and white, 

 occur ail along the steep face of this bench. They have a strike nearly 

 parallel with the river. In most cases they dip at steep angles, but in 

 places seem to fold over the front of the bluffs and lie in a more or less 

 horizontal position on the upper surface of the bench. 



A notable ieature of this bench is the very plentiful occurrence of 

 basaltic rocks. All along the bluff face there are dark irregular seams 

 of basalt; they do not lie conformably with the sedimentary strata but 

 cut across at various angles as if intruded into their present posi- 

 tion subsequently to the folding of the strata. On the upper surface of 

 the bench, and extending back to the base of the mountain slopes, are 

 very numerous sheets and masses of basalt, which break oft" in benches, 

 the fallen portions forming dark slides of debris. 



The smooth slopes of the mountains that rise behind the low bench 

 have an obscure benched appearance that is doubtless partly owing to 

 the existence of soil-covered lava-flows, but which must be chietiy the 

 result of ancient river action. 



What can be seen of the Section in the middle portion of the bench is 

 given in Section C. 



At the mouth of Bear Gulch we have some interesting features. The 

 lineof the fault here crosses the river obliquely from the north to the south 

 side. Portions of the Cretaceous strata have been caught in the irregu- 

 lar wall of the ascending schists and quartzites of the north side of the 

 fault, and appear in positions such as are indicated at d in Se(;tion D. 

 Large masses of yellowish sandstone strata just west of Bear Creek now 

 stand on edge or incline at steep angles. The Cretaceous shales and 

 shaly sandstones which form the river banks for some distance below 

 the mouth of Bear Creek dip at various angles and are very much dis- 

 located. The strata near Bear Gulch are in places quite briUiant in 

 color, probably from mineral stains which owe their presence to the 

 action of ancient hot springs. At the junction of Bear ('reek with the 

 Yellowstone, on the right bank of the former, there is at jireseut a small 

 group of springs, the deposits of which extend down to the river bank. 

 On the south bank of the Yellowstone, o])posite the mouth of Bear 

 Creek, there stands a small butte which is capped by a heavy mass of 

 ancient calca' eous hot spring deposit. The deposit is some 20 or 25 feet 

 thick, is yellowish in color, and so compact that it has, at a little dis- 

 tance, the appearance of compact limestone. The base of the butte is 

 composed of the A^ertical shales, and these are underlaid by the meta- 

 morphic quartzites that have risen beneath them. The antiquity of the 

 siliceous deposit of the capjung is made evident by the advanced state 

 of erosion of the underlying strata, as well as by the fact that the sum- 

 mit of the butte, now at an elevation of some 200 feet above the river, 

 is covered with huge rounded granite bowlders, which were doubtless 

 transported from a point far up the caQon while the bed of the river was 

 still above the level of the present sunuiiit of the butte. (See Section 

 E.) In the bed of the river beneath the butte and forming the walls of 

 the third canon which extends from this point to Junction Valley, are 



