44 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 75 



that deposited it was of lower Ordovician age, which may possibly but 

 not probably have been the age of the Wonah Ouartzite of the Sin- 

 clair Canyon section, as that is superjacent to shales carrying a Beek- 

 mantown faunule. 



To the north of the Bow Valley-Kicking Horse Canyon section I 

 have not met with any formation of Silurian age. In the Sawback 

 Range and the Main Range along the Continental Divide the Devonian 

 is superjacent to the Ordovician Sarbach formation (Beekmantown), 

 or it may rest directly on the Mons, or there may be the Ghost River 

 or Mount Wilson ' quartzite, representing the beach sands of the 

 transgressing pre-Devonian sea. 



The Beaverfoot-Brisco and early Devonian seas do not appear to 

 have extended into this eastern and northern area. Probably, however, 

 they extended north of the Kicking Horse Canyon along the western 

 side of the Cordilleran sea, west of the Continental Divide, as the 

 same type of Silurian faunas occur in Alaska, where they may have 

 migrated southward. 



VARIATION IN THICKNESS OF FORMATIONS 



Dr. J. A, Allan, in describing the Ottertail limestone of the Upper 

 Cambrian which occurs on the eastern side of the Beaver foot canyon 

 valley opposite and northeast of the Beaverfoot Range, states that the 

 formation has a thickness of about 1,640 feet (499.8 m.) on the south 

 slope of Ottertail Valley, and 5 miles (8 km.) south on Limestone 

 Peak north of Washmawapta snowfield it has an approximate thick- 

 ness of 2,450 feet (746.7 m.), indicating a thickening of over 800 feet 

 (243.8 m.) in a distance of less than 5 miles (8 km.).' 



Examples of the variation in the thickness of formations similar to 

 that of the Ottertail limestone are found the entire length of the 

 Beaverfoot-Brisco-Stanf ord Range from Kicking Horse Canyon to its 

 southern end, a distance of about 100 miles (160.9 km.). The Glen- 

 ogle shale v/ith its Ordovician graptolite fauna appears to thin out 

 and disappears somewhere between Kicking Horse Canyon and Sin- 

 clair Canyon. The lower Ordovician Sinclair formation, which has 

 a thickness of 1,655 feet (504.4 m.) at Sinclair Canyon, is not present 

 in the Sabine Alountain section 34 miles (54.7 km.) south ; the Wonah 

 Ouartzite no feet (33.5 m.) thick in Sinclair Canyon, is absent at 

 Sabine Mountain, and on the northern end of the Beaverfoot Range 

 it may be 800 -I- feet (243.8-l-m.) thick. The Mons formation 742 feet 



'■ Smithsonian Misc. Coll., Vol. 67, No. 8, 1923, pp. 463, 464. 

 ^Geol. Surv. Canada, No. 46, Geol. Ser., Memoir 55, 1914, p. 86. 



