NO. 5 PRE-DEVONIAN PALEOZOIC FORMATIONS 321 



Feet Meters 



4. Gray, arenaceous (magnesian) limestone in massive beds, 



that break up into thin, irregular layers. Some of the 

 thin layers weather buff and others dirty gray, passing 

 gradually into more and more shaly beds of bluish-gray 



color, weathering buff 22.0 6.7 



Fragments of fossils and trails. 



5. Coarse, highly arenaceous limestone 4.0 1.2 



6a. Gray siliceous shale in beds 2 to 4 feet (.6 to 1.2 m.) 



thick, weathering grayish-buff and banded 42 128 



Fauna. — Fragments of trilobites. 



6b. Finer grained shales than in 6a, and with thin layers 



of gray, siliceous, slightly calcareous shale 80 24.4 



Fauna. — 



Micromitra sp. 



Sertularian sp. 



Hyolithes cf. billingsi 



6c. Bluish-gray, exceedingly fine-grained, strong siliceous 



shale. At 65 feet (19.8 m.) the shales grow darker 



(Nlsusia and Microdiscus appear). About 90 feet 



(27.4 m.) down the shales become thinner and darker 



and in the lower 12 feet (3.7 m.) are black 228 69.5 



Fauna. — Between 30 and 40 feet (9.1 and 12.2 m.) from 

 the base the Phyllopod fauna occurs in great abun- 

 dance. , 



Total section of Burgess formation 410 125.0 



Thin-bedded, shaly, bluish-gray limestones of the 

 Stephen formation outcrop from beneath the Burgess 

 shale and extend down the slope of the mountain for 

 200 feet (60.9 m.) or more. The limestone is in 

 layers from 2 to 3 feet (.6 to .9 m.) thick that split 

 into thin, very irregular, shaly layers, largely made up 

 of crushed and broken trilobites of the genera Neo- 

 lenus, Bathyuriscus and " Ptychoparia." These lime- 

 stones bend down to the westward at nearly a right 

 angle, and are nearly vertical along the Yoho trail at 

 a point north of the Burgess shale fossil quarry. 



The lower portion of the great shale bed (6c) is 

 an exceedingly fine, compact, hard, black shale, a por- 

 tion of which has been named the Phyllopod bed. The 

 detailed section, as measured, is as follows.^ 



Feet Inches Meters 



1. Bluish-gray siliceous shale, with partings of dirty-gray 



shale I 9 .5 



2. Dirty-gray shale 8 .2 



3. Bluish-gray shale in compact layers 3 to 4 inches 



(7.6 to lO.i cm.) thick i o .3 



4. Dirty-gray shale o 2 .05 



5. Bluish-gray, tough, brittle shale 2 .05 



^ Smithsonian Misc. Coll., Vol. 57, No. 6, 1912, p. 152. 



