674 J. II. SINCLAIR CRETACEOUS OF ALBERTA, CANADA 



miles long, bounded on the north by the Bow River and on the south by 

 the North Fork of Willow Creek. 



Physiographic Features 



The physiographic features are of the characteristic foothill type so 

 well known in Colorado and elsewhere. Long hog-back ridges, remark- 

 ably straight, trending nearly north and south and parallel to the Rocky 

 Mountain escarpment, are associated with narrow valleys in which an 

 inactive subsequent drainage is witnessed by the presence of small streams, 

 small lakes in places, and swampy areas. The former are defined by the 

 uptilting of hard sandstone strata; the latter by the easily disintegrated 

 weak shales, entirely of the Benton formation. 



A characteristic feature also are the consequent streams, which, rising 

 in the Rocky Mountains to the west, have cut notches in the hog-backs 

 and, flowing directly across the district at right angles to the strike of the 

 strata, debouch on the plains to the east. These, in order from north to 

 south, are the Bow River, Sheep River, Highwood River, and Willow 

 Creek. They debouch into the plains at an average elevation of 3,200 

 feet, the average elevation of the hog-backs being about 4,000 feet above 

 the sea. 



General Character of ti-ie Strata 



The rocks of this narrow belt are almost entirely of Cretaceous age, 

 bounded on the west by the Paleozoic massive limestones of the Livingston 

 Range of the Rockies and on the east by flat-lying sediments of Tertiary 

 age. Curiously enough, the three epochs represent three distinct types of 

 structure which, as indicated above, are represented by three distinct 

 types of land forms. The Paleozoic strata bounding the foothills on the 

 west are great blocks of hard and massive limestones shoved over the 

 Cretaceous strata, en bloc, it might be said, and their lofty summits attain 

 elevations of G,000 to 8,000 feet above the sea. The Cretaceous sediments 

 are composed of sandstones and shales contorted, overturned, and faulted 

 to a remarkably confusing degree. The Tertiar}^ strata to the east are 

 flat lying, and there does not appear to be any appreciable lessening of 

 the complicated folding as one approaches these massive flat-lying Ter- 

 tiary rocks. The transition is abrupt. On one side a maze of folds, a 

 zone of broken and faulted rocks, and suddenly the gently dipping and 

 flat-lying Tertiary strata are met with. The Paleozoic rocks are moun- 

 tains ; the Cretaceous form foothills ; the Tertiary, prairies. 



