RESULTS OF RECENT RESEARCHES. 303 



1891, and the tacts then observed are believed to be of sufficient interest 

 to present to the Society. They prove — 



1. The identity of the fossiliferous strata near Great Falls with those 

 of the coal field ; 



2. The position of the formation relative to the Carboniferous and to 

 the Fort Benton rocks, as established b} r a carefully measured detail sec- 

 tion ; 



3. The occurrence of fresh-water shells above the coal; 



4. The absence of recognizable Dakota strata ; 



5. The termination of the Carboniferous deposits in a scries of shales 

 and impure limestones, stratigraphically and lithologically the equivalent 

 of the Myacites beds of the Jura-Trias of southern Montana, but carrying 

 lower Carboniferous (Spergen hill) fossils. 



The eastern portion of the field was examined by the geologists of the 

 Northern Transcontinental Survey in 1880. Professor W. M. Davis, in 

 studying the relation of the coal to the older rocks, measured two sections 

 from the Cambrian to the horizon of the coal, of which detailed notes are 

 not given. A graphic representation of these sections was published, 

 with lists of fossils determined and an interesting account of the adjacent 

 mountain region, in the reports of the Tenth census.* 



In the investigation of the coals from an economic standpoint for the 

 same survey, the coal seam was traced by G. H. Eld.red.ge from the Judith 

 basin to Belt creek, and sections of the seam, wherever opened at that 

 time, will be found in his report.f Somewhat later Professor J. S. New- 

 berry made an examination for the Great Northern railway of that part 

 of the field now worked, and mentioned the general relations of the coal 

 rocks to the underlying Paleozoic terranes, in a paper on the geology 

 and botany of the country bordering the Northern Pacific railroad. J 



Location' and Extent of the Field. 



The Great Falls coal field, as already indicated, is situated at the base 

 of the Rocky mountains in central Montana., and takes its name from 

 the town to which it is tributary, [ts proximity to Helena, the state 

 capital, and to the great mining center Butte, with the increasing market 

 afforded by the smelters and other industries of ( itvut Falls itself, makes 

 the Held of the first importance in the future developmenl of Montana. 



Coal has been found in the ECootanie rocks all along the base of the 

 mountains from the vicinity of fort Shaw eastward to the Judith basin. 



♦ Tenth Census: Mining industries, vol. sv, Washington, 1886, p 69T. 

 t [bid., p. 739. 

 Innals oi the V \ \.ce I imy ofS siences, vol. iii, 1831, no. 8. 



