NO. 5 PRE-DEVONIAN PALEOZOIC EORMATIONS 21^ 



The deposition of dark gray siliceous and calcareous sediments was 

 interrupted, after 300 feet (914 m.) had been laid down, by an 

 influx of fine, dark argillaceo-calcareous muds and occasional deposits 

 of purer argillaceous silts upon which the graptolites flourished. 

 About 100 feet (30.5 m.) of these mixed beds accumulated before 

 the order of sedimentation was reversed, 50 feet (15.2 m.) of bluish- 

 black calcareous muds were next deposited, and deposition of the 

 dark gray siliceous and calcareous sediments then continued without 

 further interruption to the close of the deposit, more than 800 feet 

 (243.8 m.) above the graptolite zone. 



Beaverfoot Formation. Burling, 1922 ' 



Type locality. — Southwestern side of the crest of Beaverfoot Range 

 south of Kicking Horse Canyon from 6 to 20 miles (9.6 to 32 km.) 



Derivation. — From Beaverfoot Range. 



Character. — Compact, hard, gray, dolomitic, rough-weathering 

 limestones with considerable gray chert in the form of small nodules, 

 stringers, and thin irregular layers. Usually in layers 6 inches (15 cm. ) 

 to 2 feet (.6 m.) in thickness. Some of the layers are less dolomitic 

 and more fria^ble after prolonged weathering, and the silicified fossils 

 and cherts weather out in strong relief ; the silicified corals are often 

 entirely free from the matrix. 



Thickness. — The limestones of this formation usually form a sheer 

 cliff or a series of small cliffs that average a total thickness of 400 feet 

 (12 1. 9 m.) in the Brisco Range. 



Geographic distribution.— The Beaverfoot has, as far as known, the 

 same distribution as the Brisco, with which it is closely associated in 

 nearly all sections of the Beaverfoot-Brisco-Stanford Range. 



Organic remains. — From the collections made by Dr. Edwin Kirk 

 of the U. S. Geological Survey, in the Beaverfoot-Brisco-Stanford 

 Range, he has identified the following : 



Beatrice a sp. 



Receptaculites sp. 



Paleofavosites sp. 



Streptelasma trilobatum Whiteaves 



Coluumaria alveolata Goldfuss 



Colnmnaria {Paleophyllum) cf. stokesi (E. and H.) 



Haly sites sp. 



Rhynchotrema cf. capax (Conrad) 



Rhynchotrema argenturbica (White) 



Zygospira cf. recurvirostris Hall 



Plectambonites cf. saxeus (Sardeson) 



' Geol Mag., Vol. 59, p 459. 



