4(5 



GEOLOGICAL SURVEY OF THE TERRITORIES. 



main streams, became so stocked with trout. One thing is certain, 

 there is no commnnicatiou for the fish with the main stream. 



Fig. 7 is intended to represent an ideal section of Soda Butte, show- 



Fig. 7, 



CAKB. LIMESTONE SECTION OF SODA BUTTE. 



ing- the pipe or orifice 

 and the manner of 

 the deposition of the 

 layers, or the growth 

 of the mound. 



The limestone that 

 cropped out for a lit- 

 tle distance below the 

 forks disappeared 

 again for about ten 

 miles up the middle 

 branch, when it re- 

 appeared on both 

 sides of the valley, 

 and continued up to 

 the Clark's Fork di- 

 vide. The snows are 

 quite deep on the 

 sit'.es of the mountains in the gorges even at this time, and it is probable 

 that they remain all the year. . The width of the valley will average about 

 one-fourth of a mile, and is thickly wooded with several kinds of conif- 

 erous trees, with here and there groups of the aspen-i3oplar. About fiv'e 

 miles above the forks, fragments of limestone began to appear on the 

 surface, and soon the regular strata commence to rise above the bed of the 

 stream, and about ten miles above, the limestones were exposed in ver- 

 tical walls on either side of the canon from beneath the conglomerates 500 

 to 1,200 feet. The upper surface is quite irregular, indicating a great 

 amount of denudation prior to the deposition of the conglomerate. The 

 limestones are yellow, brown, and in nmny localities brick-red. The mass 

 is alternately depressed or elevated ; that is, sometimes a very high ver- 

 tical wall is exposed with the strata inclining at various angles, again it is 

 depressed nearly to the bed of the stream. There is one locality near 

 the source of the Middle Fork, where the limestones rise up 1,000 to 1,200 

 feet. So far as texture aided to determine, these limestones seem to 

 be of Carboniferous age. Numerous fossils were found, which were all 

 of that age, and I saw no locality where the Silurian limestones 

 appeared to crop out. One curious fact could be observed here, which 

 shows the vastness of the eroding forces. The rocky walls on either side of 

 this caiion are alike, and reveal the fact that the entire valley has been 

 carved out of the massive rocks which must have been far more extensive 

 than we see them at present. From the source of this branch to the en- 

 trance into the main valley, a distance of fifteen miles, a mass of rock-ma- 

 terials has been worn out one-fourth of a mile in width, almost fifteen miles 

 in length, and of a thickness at least equal to the summits of the highest 

 peaks, some of which are 3,000 feet above the valley below. We cannot 

 now estimate how much of the surface may have been wasted away, 

 but the evidence is clear that no inconsiderable portion has been 

 removed. When the limestones are exposed underneath the conglom- 

 erates on one side of the caiion, the corresponding strata are seen on 

 the opposite side. The conglomerates are very nearly or quite hori- 

 zontal, the lower portion adapting itself to the irregular surface of the 

 limestone like any other sedimentary deposits. This valley or caiion is 

 only an illustration of many others. I have no doubt that the Carbon- 



