CANADIAN AND MONTANA ROCKIES 



315 



Cretaceous sediments have been charted for the entire western part of 

 the continent on the tectonic map, Plate 11. 



The Kootenay and Blairmore formations are continental in origin, and 

 reflect an uplift of the region to the west and a source of abundant feld- 

 spathic sediments. The next formation, the Colorado or Alberta shale, is 

 marine and represents a marine invasion. See chart, Fig. 20.11. The Belly 

 River that followed the Colorado is continental and resembles the Blair- 

 more. It reflects renewed uplift on the west. A local sea invaded the 

 southern foothills belt from the south, and in it the Bearpaw shale was 

 deposited. A continuation of uplift in the Selkirks resulted in the deposi- 

 tion of the continental Edmonton. Then a period of erosion occurred that 

 represents the Lance, early Paleocene, and middle Paleocene (Russell, 

 1932); and following it, the upper Paleocene Paskapoo sandstone and 

 shale were deposited. In the foothills and plains no angularity between 

 the Edmonton and Paskapoo has been noted. 



All the foregoing Cretaceous formations and also the uppermost Paleo- 

 cene beds are folded and faulted in the foothills (Russell, 1932), and 

 therefore the main deformation of the frontal Canadian Rockies occurred 

 in post-Paleocene time. 



A second but milder orogeny is noted by Bostock et al. ( 1957 ) : 



In the Flathead Valley, west of Clark Range, the Kishenehn formation of 

 very late Eocene or very early Oligocene (Upper Duchesnean) age uneon- 

 formably overlies early Mesozoic strata which are involved in the structures 

 of the southern Rocky Mountains. The strata are gently folded, dipping mainly 

 about 30 degrees northeast. These observations indicate two phases of deforma- 

 tion, the first, pre-Kishenehn and post-early Mesozoic, probably post-Paleocene 

 in age, during which the main orogenic movements took place, and the second, 

 post-Kishenehn in age, during which the Kishenehn beds were tilted. Con- 

 glomerates of the Kishenehn carry pebbles of Proterozoic rocks indicating that 

 these rocks were exposed to adjacent ranges following the first phase of the 

 deformation. 



Further evidence on the age of the uplifts associated with the orogenic 

 movements in the southern Rocky Mountains is found in conglomerates on the 

 Plains of southern Saskatchewan. The products of erosion from the uplift of 

 the southern Rocky Mountains during two phases of the deformation are 

 thought to be represented by gravels in the Cypress Hills region which carry 

 pebbles of the distinctive Proterozoic rocks and bracket in age the time of 

 deposition of the Kishenehn formation. Mammalian fossils in the Swift Current 

 Creek beds are Uintan (late Eocene) and those in the Cypress Hills formation 



are of Chadronian (early Oligocene) age. In summary, the first and main de- 

 formation in the southern Rocky Mountains took place in the interval between 

 the Paleocene and the late Eocene. Uplift and erosion occurred in the late 

 Eocene (Uintan), followed by relative quiescence during the deposition of 



CANADIAN ROCKIES 

 HIGMWOOD-ELBOW AREA 



FOOTHILLS 

 TURNER 

 VALLEY 



PLAINS 



Fig. 20.11. Cretaceous formations south of Calgary, Alberta. Lithology is sandstone and shale 

 except where conglomerates and limestones are indicated. The Colorado and Bearpaw sedi- 

 ments are marine, the rest brackish and fresh water. After Thompson and Axford (1953). 



