BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 2, pp. 349-364, PL. 13 MARCH 18, 1891 



THE CINNABAR AND BOZEMAN COAL FIELDS OF 



MONTANA. 



BY WALTER HARVEY WEED. 



{Read before the Society December 31, 1890.) 



CONTENTS 



Page. 



The Distribution of Coal in Montana 349 



The Cinnabar Coal Field 350 



Location 350 



General Geology 351 



The Mesozoic Section 351 



The Coal-Measures and the Workings 354 



The Bozeman Coal Field " __. 358 



Location, Extent and General Geology " 358 



The Horizon of the Coal-Measures 359 



Character of the Coal Seams 362 



Workings 362 



Age of the Coals 363 



Conclusion 364 



The Distribution of Coal in Montana. 



The coal-bearing rocks of Montana belong to three geological horizons, 

 all of Mesozoic age, and over three-fourths of the 145,000 square miles com- 

 prised within the boundaries of the state is underlain by these rocks. The 

 larger part of the great plains, that monotonous expanse of arid, treeless 

 country forming the eastern two-thirds of the state, is underlain by seams of 

 lignite, which occurs in great quantity and is often of exceptional purity. 

 The banks of the smaller streams and the bluffs of the rivers very frequently 

 show the outcrops of these lignite seams, and their dark lines can be traced 

 continuously for many miles in the buttes of the so-called " bad lands." 



Approaching the mountains, the low relief of the plains is broken by out- 

 liers of the Rocky Mountains, and as we near the eastern slopes of these 

 ranges the younger strata of the plains are found to be upturned upon the 



Lll— Bui.L. Geol. Soc. Am., Vol. 2, 1890. (^^49) 



