st.johx.] SECTION NORTH OF STATION XXV. 383 



hinted in the northerly inclined strata of similar appearance, which make 

 up the barrier on the northeast side of the valley in the quarter here 

 referred to. 



Three miles above Tall Creek, at the point where a little stream de- 

 scends into the valley from the abrupt northern or front spur descending 

 froni Station XXY — one of the dominating points of the eastern front of 

 the range between Fall and Pyramid Creeks which here attains an actual 

 altitude of 9,000 feet, or 3,000 feet above the Snake — opportunity was 

 afforded for the prosecution of some interesting detail examinations in the 

 sedimentaries which here make up the northeast front of the range, the 

 results of which are given below. This locality lies about three miles to 

 the northwestward of Station XXV and four miles east-southeast of the 

 debouchure of Fall Creek. As the little stream debouches from the 

 mountains its bed lies in a canon across the high volcanic bench which 

 rests against the foot of the range, the relative position of which is shown 

 in an accompanying section-diagram, the further notice of which is de- 

 ferred to the section specially devoted to the description of the physical 

 and geologic features of the lower valley of Snake Eiver. This volcanic 

 bench extends back from the river between one and two miles, when the 

 base of the range proper is reached, where, on the west side of the little 

 stream, that part of the section relating to the sedimentaries begins, ex- 

 tending thence in a south-southwest course to the crest of the before- 

 mentioned front spur, and is as follows : 



Section north of Station XXV. 



1. Gray limestone, in places light granular subcrystalline, appearing 

 hi bench outcrop at foot of ascent, much broken up, and not satisfactorily 

 showing the bedding. Dip probably southwestward, though at one point 

 certain planes, probably joint structure, pitch to the X. 25° W. at an 

 angle of 80°. Contains Sienopora or Fistulipora, crinoidal remains, Fen- 

 c.stella, Spirifer. Productus, a small Platyccras, &c, all characteristic forms 

 of the Carboniferous. This outcrop is 800 to 1,000 feet above Snake 

 Eiver, the volcanics in places even reaching a higher level on the flank 

 of the mountain. 



2. Long slope, with no rock exposures in situ, perhaps half a mile, 

 covered with groves of large pine, undergrowth, and open grassy plots. 



3. Pink, laminated brittle sandstone, almost a quartzite, forming a 

 heavy ledge, dipping gently southwestward, like the flagging of a dome 

 or arch. 



4. Bluish-drab, spar-seamed limestone, pertaining to a heavy ledge, 

 and contains a large Bellorophon. The bed dips S. 45° W. at an angle 

 of 30°, but at a neighboring exposure the inclination changes to X. 50° 

 E., at an angle of 20°, indicating the axis of a fold or undulation in the 

 strata. A few fragments of black obsidian were observed in the soil at 

 this place. 



5. Gray, heavy-bedded limestone, with irregular seams of rusty gray 

 chert or siliceous bands, in low bench exposure 75 to 100 yards south' of 

 X< >. 3. Dip 22° southwestward. Contains Productus and a large Spirifer 

 hke S. earner atus. 



6. Unexposed, sag. 



7. White, fine, granular magnesian (?) limestone, a heavy ledge, 10 

 feet exposed ; dip 35°, southwest. 



8. Eeddish-buff indurated arenaceous bed. 



9. Dark-blue and gray siliceous limestone, with dark chert ; heavy 

 bed, dip 3.5°, S. W. Spirifer, Pleurotomaria. 



