GEOLOGICAL SURVEY OF THE TERRITORIES. 



113 



are now the valleys of the Jefferson, Madison, and Gallatin Rivers, reach- 

 ing to the junction of the three streams. The hills between the Gal- 

 latin and Madison, and between the Madison and Jefferson, are Plio- 

 cene, remnants of the same beds, and when we ascend the mountains on 

 the southern border of this old lake-basin the whole plan lies spread 

 out before us. Each of the rivers has cut deeply into these Pliocene 

 rocks, and their valleys are the results of the erosion that has taken 

 place since the draining of the ancient lake. The question of priority 

 of elevation of the Bridger liange, and that into which Spring Canon 

 is cut, is one of some interest. That there has been more than one 

 force at work to give the surface its present configuration is evident. 

 The question is, whether or not they acted synchronously. The forces 

 that elevated the layers of Spring Caiiou ard those of Bridger were, 

 I take it, entirely distinct from each other and separated by long periods 

 of time. The Bridger Kange was the first to be elevated, and its eleva- 

 tion occurred probably about the end of the Cretaceous period, and be- 

 fore the beginning of the Eocene, while the range running south from 

 Spring Canon was elevated some time after the Eocene and prior to the 

 deposition of the Pliocene strata. This is proved by the foot that the 

 Cretaceous rocks on one side of the valley are conformable to the 

 Bridger Ptange and on the other side to the Spring Canon layers, 

 while the Eocene rocks are conformable only to the latter, and the Plio- 

 cene rocks have been affected by neither range. • I believe also that the 



Fig. 27 a. 



SECTION FROM SPRING CANON TO DRIDGER PEAK. 



A, Bridgor Peak; B, Spruit; Ciiuon ; C, Tertiai-y ; D, Cretaceous; E, 

 Juiassic ; r, Carboniferous; G, Drift; H,' Tertiary hills. 



elevation of the 

 Bridger Eange was 

 the more gradual of 

 the two. The eleva- 

 tion of the Spring 

 Canon layers was <lue 

 to volcanic action, 

 the center of which 

 lies to the south. 

 There have been sev- 

 eral periods of erup- 

 tion, for in the vallej^ 

 of the Yellowstone 

 Eiver we find Pliocene sandstones and marl capped by basaltic plateaus, 

 while at Fort Ellis there is nothing of the kind, and we will see in a sub- 

 sequent chapter that, some distance farther south, we find Eocene beds 

 lifted high up on the mountains. The section shown in Fig. '11a will 

 give the relations of the beds between Spring Caiiou and Bridger Peak. 

 I have referred above to the occurrence of coal near Fort Ellis. The 

 only rocks in which I noticed it were those of Eocene age. At only 

 one point has there ever been any mining attempted. This one point 

 is east of Spring Caiion, about four miles southeast of Fort Ellis. Coal 

 was discovered here in 18G7 by two blacksmiths, of Bozeman. Colonel 

 J. D. Chestnut, hearing of the discovery, offered to furnish provisions 

 to get men to work into the bed, if they would give him a -share. This 

 they did, and afterward left him sole owner of the claim, which in- 

 cludes one hundred and sixty acres. Fig. 28 is a section of the coal 

 bed, C showing the opening into it. The shaft penetrates the bed in 

 a horizontal direction, and has reached a depth of 250 feet from the 

 entrance. The width of the shaft is 14 feet at the widest part. The 

 be& of coal is considerably wider, and dips north 50° east ; angle, 80°. 

 On each side of the coal there are beds of bluish argillaceous sand- 



8 G s 



