WALCOTT.J 



SUMMARY ROCKY MOUNTAIN PROVINCE. 



329 



River quartzites and slates. The Cambrian section at this point also 

 agrees closely with that of Nevada. The Olenellus fauna occurs at the 

 base of a thick series of limestone, and in calcareous shales, 2,000 feet 

 higher up, the Middle Cambrian fauna is well developed. Where the 

 line between the Cambrian and Lower Silurian (Ordovician) is to be 

 drawn in this great series of limestone and calcareous shales is still un- 

 determined. 



ra= 



sa 



^^ 



nm 



E£! 



^m 



^FT- 



s5 



S 



T3^T. 



S 



=s 



■m: 



e5 



Sh 



B 



EK 



ES 



^^g 



2E^ 



^F 



ty.C? 



¥4 



tVcN \ 



L.C? 



17 





L.C.? 



X. MC. 



L.C.? 



14 



13 



Fig. 3.— Sections of the Rocky Mountain province, vertical scale 6,400 feet to the inch. The num- 

 ber beneath each section corresponds to the locality number on Pis. I and II. 



The presence of Olenellus gilberti 3,000 feet down in the Bow River 

 quartzite and shales gives strong reason for referring the entire Bow 

 River, Idaho, Wasatch, and Nevada quartzite and shales series to the 

 Lower Cambrian. We know that the vertical range of the fauna is 

 great in the Appalachian sections and also in British Columbia. 



As a whole the sedimentation in the vicinity of the shore line of 

 Utah was limited in amount in later Cambrian time, and consisted 

 mainly of siliceous and argillaceous muds. In the deeper sea to the 

 westward a great accumulation of calcareous sediment rests upon the 

 basal quartzite, and this continues to southern central Nevada. To 

 the northward there is a decrease in thickness of the limestones across 

 Idaho. In British Columbia the section is more like that of central 

 Nevada. 



