BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 17, pp. 1-28, pls. 1-11 May 17, 1906 



ALGONKIAN FORMATIONS OF NORTHWESTERN MONTANA 



BY CHARLES D. WALCOTT 



{Presented by title before the Society December 29, 1905) 



CONTENTS 



Page 



Introduction 2 



Stratigraphic sections 2 



Camp Creek, Mission Range section 2 



The section in general 2 



Cambrian, Flathead sandstones 3 



Algonkian, Belt terrane 3 



Camp Creek series 3 



Blackfoot series 5 



Ravalli series 7 



Resume of Camp Creek, Mission Range section 7 



Dearborn River section 8 



Location of the section 8 



Cambrian, Flathead sandstones 8 



Algonkian, Belt terrane 8 



Lewis and Clark Pass section 9 



Location of the section 9 



Cambrian, Flathead sandstones 9 



Algonkian, Belt terrane 10 



Marsh formation 10 



Helena formation 10 



Empire formation 10 



Resume of Algonkian, Belt terrane 10 



Swan Range section 10 



Location of the section 10 



Algonkian 11 



Blackfoot series — Upper Division 11 



Blackfoot series — Lower Division 11 



Notes on section from Belton, east 12 



Bad Rocks Canyon section 12 



Nyack Creek section 13 



Generalized section, Coeur d'Alene district, Idaho 14 



Generalized section from Striped peak, Idaho 15 



Note on limestones near Kalispell 15 



Unconformity between Algonkian and Cambrian 10 



Correlation of sections IT 



Algonkian sections of northwestern Montana and northern Idaho 18 



I— Bull. Geol. Soc. Am., Vol. 17. 1905 (1) 



