278 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 75 



A thick-bedded, quartzitic series with some Scolithus and fine 

 quartz conglomerate represents the Fort Mountain quartzite which 

 occurs on Redoubt (Fort) Mountain, 2 miles (3.2 km.) to the 

 southeast. 



The narrow, sharp south ridge of Mount Richardson merges into 

 a rounded ridge of pre-Cambrian sandstones and arenaceous shales 

 of the Hector formation, the actual contact of the two formations 

 being obscured by debris from the Fort Mountain quartzitic sand- 

 stones. 



. A beautiful glacial cirque, Richardson Cirque, .occurs between the 

 south ridge of Mount Richardson and the slopes of Pika Peak on 

 the northeast. At the foot of the cliffs is a small, sapphire-blue lake, 

 fringed in July with Caltha and a luxuriant emerald green sod. The 

 lake is only a mile (1.6 km.) from the Ptarmigan Pass trail, and the 

 brook flowing from it crosses the trail at the upper camp site a half 

 mile (.8 km.) below the Pass. 



The typical section was measured on the east and northeast face 

 of Ptarmigan Peak above Ptarmigan Pass and Lake from the summit 

 of the peak down to the lake and on the northeast slope down and 

 into the pre-Cambrian.^ 



MIDDLE CAMBRIAN 



Cathedral Formation p^p^ Meters 

 I. Massive-bedded, arenaceous, cliff-forming limestone, 

 mostly of a light gray color, but with a few dark, lead- 

 colored bands of more or less irregular boundaries 

 above and below. The dark bands are usually formed 

 of more thinly bedded and finer arenaceous lime- 

 stone 2.100 640.1 



Fauna. — No fossils except traces of annelid borings. 



The thickness of 2,100 feet (640.1 m.) is an estimate 

 based on the height of the mountain and the height of 

 the base of the light gray arenaceous limestone above 

 Ptarmigan Lake. 



Ptarmigan Formation 



\a. Thin-bedded, fine-grained, hard, dark, gray to grayish- 

 black arenaceous limestone 46 14.0 



Fauna. — (63b) : , 



Zacanthoides ciinon Walcott 

 Neolcnus constans Walcott 

 This bed usually breaks down to form a slope 

 beneath the massive Cathedral limestone, but in places 

 it forms a steep, low escarpment. 



Smithsonian Misc. Coll., Vol. 53, 1910, p. 429. 



