CERATOPS beds' OF WYOMING AND MONTANA 257 



Another important fact, brought out by Stone's work, is that the 

 "Laramie" of Weed's mapping east and north of the Crazy Moun- 

 tains in the Little Belt Mountain folio is really Eagle sandstone and 

 the "Livingston" of the same area includes in its lower part the 

 Claggett, Judith River, and Bearpaw formations. The Livingston 

 formation was described as resting unconformably on the Laramie and 

 older rocks and as composed largely of andesitic material, both of 

 which features played a prominent part in correlating the Livingston 

 with the Denver formation. It became necessary therefore to study 

 the lithologic character of the various formations of the Montana 

 group in this area, especially since certain beds in the Claggett and 

 Judith River were observed to have an igneous appearance. On 

 my request thin sections have been made of a number of specimens 

 collected by Mr. Stone and those have been examined by Messrs. 

 Johannsen, Calkins, and Stone. The specimens from the Eagle and 

 a few of those from the Claggett and Judith River proved to be sand- 

 stone without admixture of igneous material, but many others from 

 both Claggett and Judith River and some from the Bearpaw are 

 identified as tufaceous rock and contain much andesite, as the follow- 

 ing extracts from the report will show: 



C. M. 71. Tuff. From the Claggett formation in T. 6 N., R. 15 E., sec. 

 14. Consists chiefly of grains of plagioclase and altered lava, 

 and is probably a water-laid tuff. 



C. M. 74. Tufaceous rock. From near the top of the Claggett formation, 

 650 ft. above the Eagle sandstone, in T. 6 N., R. 15 E., sec. 13. 

 Consists of angular fragments of plagioclase and andesite, and 

 so far as seen contains no augite and no quartz. Probably 

 is tufaceous. 



C. M. 75. Tufaceous rock. From the top of the Claggett formation, in 

 T. 8 N., R. 12 E., sec. 29. Shows two pebbles of andesite 

 in a matrix like No. 15. Probably is tufaceous. 



C. M. 76. Tufaceous rock. From near the base of the Judith River for- 

 mation, in T. 6 N., R. 15 E., sec. 13. This rock is a conglom- 

 erate with subangular to rounded pebbles, chiefly of altered 

 porphyritic andesite and one pebble of fine sandstone with 

 angular grains of quartz. The specimen may be an impure 

 tuff. 



C. M. 78. Tufaceous rock. From near the base of the Bearpaw, at the 

 mouth of Lost Horse Creek, T. 7 N., R. 11 E., sec. 17. Con- 

 sists of angular grains of feldspar, lava, augite, magnetite, and 

 quartz, with considerable chlorite. It is distinctly a tufaceous 

 rock. 



