570 



EEPORT UNITED STATES GEOLOGICAL SURVEY. 



BANNACK RANGE. 



The summit of the Bannack Range was the western limit of our work. 

 It extends along the western side of Marsh Creek Valley, above wliieb 

 its highest peaks rise a little over 4,000 feet. The range consists of two 

 somewhat isolated mountain masses eight or ten miles apart. They arc 

 connected, however, by a low ridge, so that, geologically, the range is 

 continuous. The portion between the two masses was not visited. In 

 the northern portion two stations (Nos. 77 and 78) were located, one of 

 which was visited by me, and in the southern portion Station 135 was 

 located. 



The canon of the Portneuf, cut across the northern end of the range, 

 shows it to be a well-defined anticlinal, quartzites, slates, and limestones 

 outcropping there, and showing dips in east and west directions, as 

 already noted in a preceding portion of this chapter. All the beds out- 

 cropping in the canon that enter into the fold are highly metamorphosed. 

 The same beds are shown on the eastern slopes of Station 77, where the 

 following section was made : 



Base. 



/Section Xo. 22, from Station 77 eastward. 



Feet. 



1,600 



1 



} 1,560+ 



1. "White quartzite ^ 



2. Light-yellowish argillaceous slates, in lamina? of about a quarter of an I 



inch thickness, with pyrite | 



3. White quartzite )■ 



4. Sombre metamorphosed quartzitic sandstones, with roimded quartzitic 



pebbles. Most of the sandstones are of a dark-greenish, almost black 

 color, -with grayish layers made up largely of grains of quartz 



5. Dark- gray quartzite 



6. Silvery gray micaceous slates 



7. Laminated gray slates i> 1, 900+ 



8. Gray micaceous slates 



9. Green and gray chloritic slates, quartzitic J 



10. Olive-green chloritic slates, with smooth surfaces. On some of the^ 



layers there are indistinct mud markings and other markings somewhat 

 resembling fucoidal remains, although they may be the result of im- 

 perfect borings by worms 



11. White quartzite 



12. Greenish-gray indurated argillaceous slates and shales, with bands of 



gray and white quartzites > J 



13. Gray and yellow hard limestone in two bands; these limestoues are" 



covered, and were recognized from a few obscure outcrops 



14. Quartzitic argillaceous slates 



15. AVhite quartzites 



16. Pink quartzites ; some of these are conglomeritic and have the appear- 



ance of metamorphosed conglomeritic sandstones ; some of the layers 

 are quite red in color 



17. Yellowish slates 



18. Pink quartzites ; some of the layers of these quartzites are green on the 



surfaces or planes of separation , 



Total , 5,710+ 



In layer No. 2 cubical crystals of oxide of iron are numerous ; some of 

 them are nearly two inches on a side. These beds are probably the 

 same that have been referred to the Cambrian by Emmons and Hayne 

 in their districts south of ours. 



In Box Elder Canon, on the western side of the Wahsatch Eange, 

 almost due south of the locality of the section given above, they consist 

 according to Hague* of quartzites and siliceous slates, with some mica- 



* U. S. Exploration of the 40th Parallel, Vol. II, p. 403. 



} 650+ 



