NO. I FORMATIONS OF BEAVERFOOT-BRISCO-STANFORD RANGE 43 



DISCONFORMITY AT THE BASE OF THE SILURIAN 

 BEAVERFOOT FORMATION 



The Wonah Quartzite (pi. 4, fig. i) beneath the Beaverfoot for- 

 mation is now assumed to represent the initial beach sands of the 

 Silurian (= Richmond) transgression in the same manner that the 

 Mount Wilson ^ quartzite represents the beach sands of the Devonian 

 transgression as it occurs at the headwaters of the Clearwater and 

 Saskatchewan Rivers in Alberta. 



Dr. Allan found on the crest of the Beaverfoot Range 15 miles 

 (24.1 km.) southeast of the Canadian Pacific Railway, a quartzite 800 

 feet (243.8 m.) in estimated thickness that was quite free of impurities 

 and formed of angular colorless quar*;z grains. This quartzite ap- 

 peared to be conformably superjacent to the dark argillaceous shales 

 of the Glenogle formation and subjacent to a massive-bedded gray 

 dolomite carrying fossil corals. This fauna is presumably the same as 

 that of the Beaverfoot formation (ante, p. 13), to the south in the 

 Sinclair Canyon section. 



Fifty-two miles (83.6 km.) to the south in the Sinclair Mountain- 

 Wonah Ridge section, the Glenogle graptolite shales are absent 

 beneath the Wonah Quartzite, and at Sabine Mountain 36 miles (57.9 

 km.) still further south the Wonah quartzite, Glenogle and Sinclair 

 shales and over 3,000 feet (914.4 m.) in thickness of the Mons forma- 

 tion are absent, the massive Beaverfoot limestones resting conform- 

 ably along several miles of outcrop on the shales of the lower portion 

 of the Mons formation. 



Similar conditions as those in the Sinclair Canyon section exist far 

 to the south in northern Utah ' where the Swan Peak Quartzite, 500 

 feet (152.4 m.) in thickness is superjacent to the Garden City lime- 

 stone in which an OrdoA-ician (Beekmantown) fauna occurs. Above 

 the Quartzite the Fish Haven dolomite, 500 feet (152.4 m.) in thick- 

 ness, contains a fauna (Riclimond) that may be compared with that 

 of the Beaverfoot limestone. Above the Fish Haven dolomite there 

 is a Silurian (Laketown) dolomite, 1,000 feet (304.8 m.) thick, that 

 corresponds to the Brisco formation of the Sinclair section. To com- 

 plete the correlation between the two widely separated sections, the 

 St. Charles formation beneath the Ordovician Garden City limestone 

 is known to contain essentially the same fauna as the Mons formation. 



The Swan Peak Quartzite carries a fauna referred to the lower 

 Ordovician^ (Chazy ?) which indicates that the transgressing sea 



^ Smithsonian Misc. Coll., Vol. 67, No. 8. 1923, p. 464. 

 ' Amer. Jour. Sci., 4th Ser., Vol. 86, 1918, pp. 406-411. 

 ■* Loc. cit., p. 409. 



