PRE-CAMBRIAN ALGONKIAN ALGAL FLO?A 



99 



The Newland limestone of the Belt series is about 2,000 feet 

 (630 m.) in thickness and the algal forms are reported by Collen 

 as occurring in it from base to summit. These include Newlandia, 

 Greysonia, Camasia, etc. Collenia is abundant in the Spokane shales 

 3,000 to 4,000 feet (960 to 1200 m.) above the Newland limestone. 



The preceding examples prove that the algal forms extend 

 through several thousand feet of strata and that they are so 

 abundant as to form reefs or banks of fossil algae in the section. 



Stratigraphic position. — As the principal groups of fossils occur 

 in the Beltian series of formations the typical section is introduced 

 here and the position of the genera indicated as they occur in 

 the several formations. The section is one obtained during a re- 

 connaissance of the Belt Mountains in 1898. The thickness assigned 

 to the various formations is based on fairly careful reconnaissance 

 estimates.^ . 



SECTION OF BELT SERIES 

 Cambrian — Flathead sandstone. 



FEET 



Unconformity 



Marsh shales 300 



Helena limestone 2,400 



Empire shales 600 



Spokane shales 1.500 — Collenia undosa 



r- , , (Annelid trails, 5 spp. 



Greyson shales 3,ooo -^ „ , . , / -^ ^^^ 



ll-ieltina danai 



Newlandia concentrica 



Newlandia frondosa 



Newlandia lamellosa 



Newlandia major 



' Camasia spongiosa 



Weedia tuberosa 



Kinneyia simulans 



Greysonia basaltica 



Copperia tubiformis 



Chamberlain shales 1,500 



Neihart sandstone 700 



Newland limestone 



2,000 



Unconformity 



Archean complex 



Bull. Geol. Soc. America, Vol. lo,- 1899, pp. 201-215. 



