348 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 75 



MIDDLE CAMBRIAN 

 MuRCHisoN Formation p^^^ ^^^^^^ 



Exposed beneath formation above. 



la. Massive-bedded, gray, arenaceous limestone 20 6.1 



lb. Massive-bedded, dark gray, very finely arenaceous lime- 

 stone that breaks down into thin, irregular layers on 

 weathering 95 28.9 



Fauna. — Fragments of trilobites, one of which was a por- 

 tion of the cephalic shield of a Ptychoparia. 



ir. Bluish-gray, thin, irregularly bedded limestone 105 32.0 



Total of Murchison formation 220 67.0 



Below ic the rocks are covered by talus down to the 



level of the canyon bottom. 

 The Murchison formation is best exposed in the 



Siffleur section, 25 miles (40.2 km.) east northeast of 



Glacier Lake. 



A fine section is exposed on Mount Murchison (11,300 feet, 

 3,444.2 m.) from the Carboniferous dow^n into the Sullivan forma- 

 tion of the Upper Cambrian, but it was not practicable for me to 

 examine it (see pi. 93), and the Siffleur River section a iew miles 

 distant ofifered a much better opportunity to get at the Cambrian 

 formations beneath the Arctomys formation down into the Lower 

 Cambrian. 



BEAVERFOOT-BRISCO RANGE 



Note. — The outcrops of early Paleozoic rocks along the Rocky 

 Mountain Trench that have been studied by Dr. Walcott were re- 

 cently described by him. See Geological Formations of Beaverfoot- 

 Brisco-Stanford Range, British Columbia, Canada. Smithsonian Mis- 

 cellaneous Collections, Volume 75, Number i, 1924. — C. E. R. 



ROBSON PEAK AREA 



The Robson Peak massif is one of the most beautiful and instruc- 

 tive mountain massifs in the Canadian Rockies. Its scenic qualities 

 are unsurpassed, and for geological study it is almost unequalled 

 (pis. 94-99) . Eroded from a block of Cambrian limestones, sandstones, 

 and quartzites, more than 12,000 feet (3,657.6 m.) in thickness, the 

 peak is the source of a great glacier on its northeastern slopes (pi. 94) 

 and minor glaciers on the northwest. On the southwest it rises 9,752 

 feet (2,972.4 m.) from Lake Kinney (pi. 95). 



