14 



C. D. WALCOTT ALGONKIAN FORMATIONS OF MONTANA 



stones. The Castle Mountain rocks form tine ridges and peaks along the 

 Kocky Mountain divide for many miles. There is evidently a fault on 

 the east, as the strata rise and end abruptly as far as could be seen. A 

 species of Eaphistoma was found in the shaly limestone 2,000 feet or 

 more above the base of the limestones. Only a few hours were available 

 for the study of this most interesting section, as snow began falling and 

 continued until it was several feet in depth. 



This note indicates the presence of the upper red beds of the Camp 

 Creek Algonkian series, with the Cambrian and Ordovician strata above. 



GENERALIZED SECTION, CCEUR D'ALENE DISTRICT, IDAHO 



The following is a generalized tabular section of Algonkian rocks in the 

 Cceur d'Alene district of Idaho, prepared by Mr F. C. Calkins : 



No. 



Name. 



Striped Peak for- 

 mation. 



Wallace forma- 

 tion. 



Saint Regis for- 

 mation. 



Revettquartzite. 

 Burke formation. 



Prichard slate. . . 



Description. 



Thick- 

 ness 

 in feet. 



Sandstones, siliceous, generally flaggy to 

 shaly ; colors mostly green and purple ; 

 characterized by shallow-water features, as 

 ripple marks, sun cracks, etcetera. 



Thin bedded sandy shales, underlain by 2,500 

 rapidly alternating thin beds of argillite, 

 calcareous sandstone, impure limestone, and 

 indurated calcareous shale ; these underlain 

 in turn by green siliceous argillites ; shal- 

 low-water features throughout ; slaty cleav- 

 age common. 



Sandstones, generally flaggy or shaly ; usually 

 fine grained and much indurated ; colors 

 mostly green and purple; characterized by 

 shallow-water features. 



White quartzites, generally rather thick 1,000 

 bedded; interstratified with subordinate | 

 quantities of micaceous sandstone. 



Gray, flaggy, fine grained sandstones and 1,700 

 shales, with interbedded purple quartzitic 

 sandstone (the proportion varies widely in 

 different parts of the district) and white j 

 quartzite; the formation characterized \ 

 throughout by shallow-water features. 



Mostly blue black, blue-gray to light gray 8,000 + 

 slates, generally distinctly banded ; consid- 

 erable interbedded gray sandstone ; upper 

 portion characterized by rapid alternations 

 of argillaceous and arenaceous layers, and by 

 shallow-water features ; base not exposed. 



Total 15,000 



