BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 3, pp. 301-330 June 28, 1892 



TWO MONTANA COAL FIELDS. 



BY WALTER HARVEY WEED. 



(Read before the Society December 30, 1891.) 



CONTEXTS. 



Page. 



1. The Great Falls Coal Field 301 



Introduction 301 



Location and Extent of the Field 303 



Configuration and Structure 304 



The geological Column . . 305 



Sections 305 



The Carboniferous 3C8 



The Jurassic 309 



The Kootanie 309 



The Dakota 310 



Descriptive Geology 311 



Sandcoul£e Basin 313 



Structure 313 



Sandcouli'e Coal Mines 316 



Belt ( 'reck I'.asin and Mines 318 



( >ther Parts of the I Jreat Falls Coal Field 322 



Age of the ( rreat Falls Coal 322 



2. Notes on the Rocky Fork Coal Field of Montana 324 



Locat ii m and general Features 324 



Extent of the Field 325 



The ( !oal Measures 325 



St ructure 325 



hr. I Lodge Mines 320 



Bear ( !reek Mines ::2S 



A.ge of the Rocky Fork < !oal 329 



/. THE CHEAT FALLS COAL FIELD. 



I NTRODl « TION. 



Near the rapidly growing city of Groat Falls, Montana, the Missouri 

 river emerges from the Belt mountains ami begins it< long eastward 

 course through the groat plains. The rapidly flowing stream soon com- 



X I.I I'.i ii oi;..i.. Soc. Am., Vol ::. 1891. 01) 



