UPPER CRETACEOUS. 687 



Generalized section of sedimentary rocks in the Lewistown coalfield. 



Feet. 



Claggett formation (Upper Cretaceous): White and brown sandstone in lower part and greenish 

 sandy shale above. 



Eagle sandstone (Upper Cretaceous) ; 



Shale, dark bluish, containing carbonized wood fragments 5 



Sandstone, soft, yellowish, cross-bedded, containing iron concretions and woody fragments.. 53 



Sandstone, soft, white, usually without bedding 170 



Sandstone, white, with coaly layer at top 10 



Colorado shale (Upper Cretaceous) : ' 



Shale, dark gray to black, with a few thin sandy members 720 



Sandstone, hard, greenish, weathering brown, fine grained, ferruginous 3 



Shale, dark gray to black, with a hard bed 420 feet above base 675 



Sandstone, grayish brown, thinly bedded, containing an abundance of fish scales (supposed 



Mowry) 47 



Shale, dark gray to black, alternating hard and soft layers 890 



Sandstone and shale, alternating, brownish in color throughout .-. . . 25 



Kootenai formation (Lower Cretaceous) : 



Shale, maroon, argillaceous, 200 



Sandstone, grayish, coarse grained, cross-bedded 8 



Shale, maroon, argillaceous 60 



Sandstone, gray, coarse grained, cross-bedded 25 



Shale, maroon, argillaceous 72 



Sandstone, massive, coarse grained to pebbly, weathering soft gray 50 



Coal and coaly shale 10 



Shale and sandstone, alternating; the shale is sandy and the sandstone thinly bedded 87 



Morrison formation (Jurassic?). 



The above section, being compiled from measurements made in several places in the field, 

 should not be considered as a type of any one locality. 



The Colorado shale decreases in thickness northward from the Big Snowy Mountains, for a 

 section of that formation to the south of the uplift shows that the interval between the Kootenai 

 red shale and the Eagle sandstone is 2,400 feet, whereas the same interval 15 miles northeast of 

 Lewistown is less than 1,600 feet. 



Throughout the field the Kootenai is fairly uniform in tliickness, although the individual 

 members comprising the formation vary locally. As a formation it is readily distinguished 

 by the bright maroon-colored shales and by the coarsely cross-bedded sandstone just above the 

 coal. 



In 1908 Stone ^®* gave an account of the Cretaceous and Tertiary rocks surround- 

 ing the Crazy Mountains, west of longitude 115°. Further studies in 1908-9 by 

 Stone and Calvert ^'^ led to a revision of the classification and nomenclature, which 

 is expressed in the following table and notes abstracted from their report : 



Stratigraphy of the Upper Cretaceous and early Tertiary in the vicinity of the Crazy Mountains, 



Montana. 



Fort Union formation, 4,000-|- feet: Massive sandstones and intercalated shales. 

 Lebo andesitic member, 450-2,200 feet: Fort Union fossils; Torrejon 

 mammals. 



Lance formation ("Laramie" or "Ceratops beds"), 1,000-2,400 feet: Light- 

 gray sandstone and variegated shales. (Stanton thinks equivalent to 

 Laramie of Denver Basin. Knowlton thinks is Fort Union.) 



Lennep sandstone, 250-460 feet: Dark-colored sandstone with intercalated 

 shales. Few fossils. Not definitely correlated with Fox Hills sandstone. 



Bearpaw shale. 



Judith River formation. 



Claggett formation. 



Eagle sandstone . Livingston flora n early through this sandstone . 



Colorado. 



Kootenai (Lower Cretaceous). 



Jurassic. 



Livingston formation as 

 originally defined for 

 a lithologic unit (an- 

 desitic material). 



