152 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 75 



brian." ' A detailed study of the Ross Oiiartzite and the Sir Donald 

 Quartzite may result in the discovery of a fauna or of an uncon- 

 formity that will serve as a boundary between the Beltian and the 

 Cambrian, if the latter is actually present in the Selkirk Mountains. 

 It is my present opinion that the troughs and embayments of the 

 Cordilleran Geosyncline in Proterozoic Beltian time were filled with 

 fresh or brackish waters that had for long periods very slight con- 

 nection, if any, with either the Pacific or Arctic Oceans. The land 

 surface of the continent then extended out to the margins of the 

 continental platform, and the epicontinental bodies of water dis- 

 charged their overflow into shallow streams that finally reached the 

 oceans through deep and narrow channels. As far as known there is 

 little if any evidence of the existence of open seaways connecting the 

 inland seas and the oceans during Proterozoic time. Any sediments 

 brought by streams were carried out to the margin of the conti- 

 nental shelf and deposited on the steep slopes descending to the 

 abyssal depths of the oceans. This almost complete separation of the 

 epicontinental waters from the oceans serves to explain the nearly 

 entire absence of marine faunas in the sandstones, shales, and lime- 

 stones of the Beltian series of formations, and the presence of great 

 algal deposits and of a few species of invertebrates of marine deriva- 

 tion that became adapted to a fresh water habitat after working their 

 way up a favorable stream to the inland bodies of water. In no other 

 way can I explain the presence of a few fossil forms in narrow bands 

 of shale and sandstone in the Beltian formations of the Cordilleran 

 Geosyncline in Montana'' and the absence of the marine faunas of 

 Lipalian time '' that preceded the marine faunas accompanying the 

 flooding of the Cordilleran and Appalachian Geosynclines at the be- 

 ginning of Lower Cambrian time. 



TROUGHS OF PALEOZOIC TIME 

 Plate 25 and fig. 14 



In the latitude of the ]>ow-Kicking Plorse Rivers the earliest of 

 these troughs was the Bow Trough on the eastern side of the geosyn- 



^ Geol. Surv. Canada, Tran.-,continental Excursion No. C i. Guide Book 

 No. 8, pt. II, 1913, p. 137. 



" Bull. Geol. Soc. America, Vol. 17, 1906, pp. 1-28. 



* Smithsonian Misc. Coll., Vol. 57, No. i, 1910, p. 14, Footnote: "Lipalian 

 (XetTTw) is proposed for the era of unknown marine sedimentation between 

 the adjustment of pelr,gic life to littoral conditions and the appearance of the 

 Lower Cambrian fauna. It represents the period between the formation of 

 the Algonkian continents and the earliest encroachment of the Lower Cam- 

 brian sea." See also Vol. 64, No. 2, 1914, p. 82. 



