NO. 5 PRE-DEVONIAN PALEOZOIC FORMATIONS 201 



The presence of this great stratigraphic break at the base of the 

 Devonian near Elko and the upper Columbia River Valley proves 

 that conditions existed on the western side of this portion of the 

 Cordilleran Trough in Silurian, Ordovician, and part of Cambrian 

 time, similar to those that prevailed on the eastern side in the Ghost 

 River area at the same period. It was a time of irregular and slight 

 sedimentation on the gently sloping pre-Cambrian strata forming the 

 southwestern and western shore and adjoining shallow sea of the 

 Cordilleran Geosyncline, while in the Bow, Goodsir and Beaver foot 

 Troughs a great thickness of sediments was accumulating. 



Devonian transgression. — The Devonian transgression recorded so 

 clearly in the Rocky Mountains of Alberta and British Columbia has 

 been reported from the Ozark uplift in Missouri ^ where the De- 

 vonian rests unconformably on the Canadian Jefferson City dolomite 

 (Beekmantown). More recently the following statement occurs in 

 a report on the Devonian of Missouri ^ " In central Missouri the oldest 

 Devonian rocks are Middle Devonian in age, and the youngest under- 

 lying rocks are older than the Niagaran of the Middle Silurian. The 

 time interval between the youngest underlying rocks and the oldest 

 Devonian probably ranges between three million and ten million years 

 in different sections. During this time some 5,000 feet [1,524 m.] 

 of sediments were deposited in places in New York and Pennsylvania." 



The Devonian transgression is also beautifully shown by Dr. L. F. 

 Noble in a series of sections in the Grand Canyon of Northern Ari- 

 zona, where the Devonian rests unconformably on the Upper Cam- 

 brian.^ Within the Cordilleran area south of the Forty-ninth Parallel, 

 the base of the Devonian is superjacent to various formations in 

 different areas and sections. At this time the great Middle Devonian 

 submergence extended over more than one-third of the North Ameri- 

 can continent. 



FOLDING OF PRE-DEVONIAN SEDIMENTARY FORMATIONS OF 



THE CORDILLERAN GEOSYNCLINE OF THE 



CANADIAN ROCKY MOUNTAINS 



The area selected for consideration includes the drainage basin of 

 Bow River from the Rocky Mountain front westward to the Conti- 

 nental Divide, and on the west of the Divide the drainage basin of the 

 Kicking Horse River and the streams to the north and south that flow 

 west into the Columbia River. This area is about ^2 miles ( 1 15.8 km.) 



^Journ. Geol., Vol. XXX, No. 6, 1922, pp. 450-458. 



^Missouri Bureau of Geology and Mines, Vol. 17, 2d ser., 1922, pp. 4, 5. 



'U. S. Geol. Surv., Prof. Paper 131-B, 1922, pi. XX. 



