GEOLOGY OF HELLGATE AND BIG BLACKFOOT VALLEYS 577 



3. The Tertiary is identified only in the valley of the Hellgate near Missoula 

 and doubtfully in township 10 north, range 11 west. 



4. A calcareous phase of the Cretaceous supposed to belong to the Niobrara, car- 

 rying Inoceramus and Ostrea. 



5. Green shale of the Cretaceous appears to be several hundred feet thick. 



6. Gray, shaly sandstone (Cretaceous) is in some places composed in part of a 

 conglomerate. Thickness, 150 feet. 



7. Black slate, frequently a black shale, appears about a mile east of Drummond. 

 This slate (shale) contains a bed of coarse conglomerate which at other places 

 seems to be reduced to a sandstone. Thickness varies from 300 to 500 feet. 



8. White quartzite, varying to sandstone, 30 to 400 feet. 



9. Dark, nearly black limestone, 30 to 100 feet. This contains numerous gastro- 

 pod fossils and serves as a datum for working out stratigraphy seen at Drummond. 



10. Fine, white, cherty quartzite, 50 feet. This varies to a gray sandstone. 



11. Coarse, red shale, 50 to 100 feet. 



12. Gray sandstone, 800 feet. This carries sometimes heavy beds of green and 

 clack shales. 



13. Black limestone, weathering buff, 75 to 150 feet. Dense, with conchoidal 

 fracture. 



14. Red sandstone, 50 feet. 



15. Red sandstone and red shales, 150 feet. 



16. Red sandstone, 20 feet, with some conglomerate, perhaps embraced in r.ed 

 shale. 



17. Red shales and gray sandstones that weather red, 200 feet. 



18. Gray sandstones, with Gryphsea, containing some conglomerate, 35 feet. 



19. Shaly red sandstones and shales, 200 feet. In this sandstone is sometimes 

 a conglomerate with quartzite and black pebbles. 



20. Quartzite, reddish, 600 to 700 feet. Usually makes a prominent ridge ; often 

 contains pockets of hematite glistening with quartz facets. 



21. Shales with a little sandstone, 200 to 300 feet. Usually red, but with some 

 green and gray. Carries kidney iron ore. 



22. Limestone, 200 to 300 feet, with gastropods (and Sarcinulaf). 



23. The main limestone mass, 2,700 feet; holds spirifer and crinoids; is the 

 chief feature in the first hill-ranges of the region northward from Bearmouth and 

 Garrison. 



24. Black limestone (Trenton?), 100 feet. 



25. Shale, reddish and often very silicious, 50 feet. 



26. Qiartzite (Potsdam?), 500 feet. Reddish to pinkish, and to white, some- 

 times spotted with buff white, passing to a fine conglomerate. 



27. Quartzite (Potsdam?], 1,000 feet. Green, schistose, impure. 



28. Argillitei Kintla, main mass), 3,000 feet. Red, green, and gray; fine-grained, 

 like flint, thin-bedded, and with occasional intraformational conglomerates. 



29. Red quartzite (Kintla), 1,500 feet. Coarser, varying to a fine conglomerate; 

 composes "Mineral hill," north from Missoula. 



30. Shaly argillite (Kintla), 700 feet. Red and gray, weathering to small frag- 

 ments. 



31. Red quartzite (Sheppard), 200 feet. Micaceous, fine grained, dark red. 



32. Limestone (Siyeh), 3,000 feet. Light gray to dark gray, often brownish 

 from iron ore, frequently shaly from much clay. Generally dolomitic, finely strati- 

 fied, mural in aspect as a result of faulting. 



