THE PROTEROZOIC ERA 53 



Distribution of the Algonkian. — As already stated, perhaps 

 the largest Algonkian area in North America is that of the Rocky 

 Mountains in the northern United States and southern British 

 Columbia. The well-known Lake Superior district of Algonkian is 

 also of large extent. There are considerable areas in eastern Can- 

 ada west of Hudson Bay, and smaller areas in Newfoundland, 

 Nova Scotia, the Piedmont Plateau, at several places in the Missis- 

 sippi Basin, Texas, Arizona (especially in the Grand Canyon), 

 Nevada, and at various places in the Rocky Mountain system 

 throughout the United States and Canada. 



Foreign Algonkian. — Algonkian rocks are thought to exist in 

 all continents. In the Highlands of Scotland, the Torridon sand- 

 stones and shales, about 10,000 feet thick, are quite certainly of 

 Algonkian x age, since they lie unconf ormably between the Archean 

 complex below and well-defined Cambrian above. 



The large pre-Cambrian rock area in Scandinavia, which in 

 many respects is similar to that of Scotland, also contains consid- 

 erable bodies of sediments (at least 10,000 feet thick) of Algonkian 

 age, the term " Algonkian" having actually been applied there. 

 As in the Lake Superior region, iron ore occurs in some of the 

 Swedish Algonkian. 



In Finland, France, Germany, Spain, and probably in India 

 and Brazil, Algonkian rocks are known. 



It should be noted that in several of the foreign countries 

 there appears to be a division of the Algonkian system into at 

 least two series separated by unconformities. 



Life and Climate of the Proterozoic Era. — As has been men- 

 tioned, determinable fossils have been found in the upper Algon- 

 kian rocks of Montana and the Grand Canyon of the Colorado. 

 These fossils include Worm tracks, a Brachiopod, and fragments 

 of Crustaceans. In Europe a few similar fossils have been found. 

 Recently the discovery of Radiolarians in the Proterozoic rocks 

 of France has been reported. "The traces of pre-Cambrian life, 

 though very meager, are sufficient to indicate that the develop- 

 ment of life was well advanced long before Cambrian time began. 

 . . . Stratigraphically, this fragment of what must have been a 

 large fauna occurs over 9,000 feet beneath an unconformity at the 

 base of the upper portion of the Lower Cambrian in northern 



1 Thus far the term "Algonkian" has not often been used in foreign 

 countries. 



