RELATION OP en A I, ROCKS TO THE PALEOZOIC. 305 



The gently inclined strata of the Great Falls coal field rest conformably 

 upon the Paleozoic terranes Hanking the granitic axis of the Belt moun- 

 tains, the easternmost range ol the Rocky mountain cordillera of this 

 locality. In these steeply upturned and folded Paleozoic strata the Cam- 

 brian, Silurian. Devonian and Carboniferous rocks have been recognized 

 by means of fossils. The massive white limestones of the Carboniferous 

 form the foothill country and pass beneath a series of gypsiferous red 

 sands and limy shales long thought to represent the Jura-Trias but re- 

 cently found to contain Carboniferous fossils, and these are in turn over- 

 lain by the sandstones and shale belts of the Great Falls formation. To 

 the northward these coal rocks are in turn covered by a heavy series of 

 strata, that pass into typical Fort Benton beds as identified by Professor 

 Newberry* 



The Highwood mountains, whose proximity to the chains formed by 

 the uplifts of the eastern Cordillera would suggest a similar origin, arc 

 really a remnant of still higher Cretaceous beds, preserved during the 

 erosion of the surrounding country by a network of dikes and sheets 

 whose injection produced an induration of the strata that has left them 

 as a record of the sediments once covering this part of the plains. Toward 

 the cast and west this same general structure, with local modifications, 

 continues along the base of the Rocky mountains. 



The geological Columx. 



Sections. — The entire geological column, from Archean gneiss to the 

 shales of the Foil Benton group, is well exposed along the course of Belt 

 creek. This stream, rising in the Belt mountains, flows for several miles 

 westward along the strike of the Paleozoic limestones, and then turning 

 northward has cut the picturesque Sluice-box canyon through massive 

 Paleozoic beds, and reaches the more readily eroded clays ami sandstones 

 oftheMesozoic. At the lower end of Sluice-bos canyon, near Riceville, the 

 Paleozoic lime-tones dip deeply northward beneath the arenaceous beds 

 of the Gypsum series and the overlying gray shales. Starting at this 

 point, a continuous section was measured from the massive mountain 

 Limestones of the Carboniferous to the beds of supposed Fori Benton age 

 which overlie the coal-bearing strata and form licit butte. These meas- 

 urements are given in the natural order. 



The following table shows, in considerable detail, the section (repre- 

 sented graphically in figure - I exposed in Bell butte: 



♦ School ..i Min. - Quarterly, v.. I. viii, 1887, p. 327. 



