42 GEOLOGICAL SURVEY OF THE TERRITOEIES. 



15. High wall of quartzite, rising at one point 150 feet, with intervals 



of red banded shale. 100 feet. 

 IG. Three beds of qnartzite, with slaty intervals. 200 feet. 



17. Bluish-green shale, full of Jurassic fossils. 150 feet. 



18. Dike of trachyte 50 feet wide. Inclines 70°. Shown in Fig. at c. 

 10. lilack slate, metamorphosed when it is in contact with the dike-ma- 

 terial. 200 feet. 



20. A huge wall of brown arenaceous limestone. 80 feet. 



21. Yellow and red banded arenaceous clay, giving name to the mount- 



ain by its bright-red color. 75 feet. 



22. Several beds of arenaceous limestone, with partings of clay, very 



thin; some of it with a reddish tinge; carboniferous fossils. 

 500 feet. 



23. Massive limestone, extending down to the metamorphic quartzites, 



on which it rests uucouformably. 1,500 to 2,000 feet. 



The fossils from bed 17 are enumerated in the catalogue by Mr. Meek. 



The lower portion of the limestone of bed No. 23 is^full of geode cavi- 

 ties, lined with crystals of calc-spar. The rock is very bard, compact, 

 brittle, easily fracturing into small angular fragments, the whole mass 

 resisting the atmosphere quite successfully. The greater portion of 

 this limestone is, most probably, of Carboniferous age; but I have no 

 doubt that the lowest part is Lower Silurian, though it differs much in 

 texture and general a])pearauce from the Silurian strata in the Gallatin 

 Valley. The exact line of sei)aration between the Silurian and Carbon- 

 iferous is diflicult to determine. Tbe partial metamorphosis of the 

 lower limestones has rendered this more obscure. The dike, as shown 

 in the Fig. at c, is the most remarkable feature in this section. It may 

 be regarded as the line of separation between the Carboniferous and 

 Jurassic strata. The dark Carboniferous shales have been changed into 

 slates on either side of the dike, and jjortions of the slate are attached 

 to the mass which now rises above tbe side of the mountain. At the 

 lower part of the mountain the igneous matter seems to have been thrust 

 up between the strata and to have tilled the cavities like a mold, but 

 toward the top it has apparently cut across the layers slightly, producing 

 some singular faults. 



Continuing eastward beyond the Cretaceous clays as noted in the sec- 

 tion, we find a vast series of arenaceous clays, sandstones, quartzites, 

 arenaceous limestones, with beds of lignitic clay, and good coal 6 or 8 

 feet thick. I estimated the thickness of this Coal group at 2,000 to 

 3,000 feet, and this estimate may be too low. There is much confusion 

 in the position of the beds, some of them inclining 45° to 50° for a. lit- 

 tle distance, and then suddenly becoming almost horizontal, inclining 

 5° to 10°. Yet there seemed to be no want of conformity. There is a 

 kind of irregular synclinal here, by which the Coal group has been 

 crushed together in such a way as to produce chaos, so far as position 

 is concerned. 



From the Cinnabar Mountain the beds seem to incline almost south- 

 west, while from the high mountains between the Gallatin and Y'el- 

 lowstoue the internal forces seem to have operated in an opposite 

 direction. Thus, within the space of six or eight miles, extending 

 from the summit of Electric Peak to the Y^ellowstone River, we have 

 the full series of sedimentary rocks from the Silurian to the limits of 

 the Coal strata inclusive, forming a synclinal. The Cretaceous beds, 

 which are noted as the black shales in the section, may be seen high up 

 on the sides of the mountain, dipping about northeast at an angle of 



