46 HISTORICAL GEOLOGY 



Archean rocks are also known in Finland, France, Bavaria, 

 Bohemia, Spain, India, Australia, China, and Japan. 



Life and Climate of the Archeozoic Era. — If the term 

 "Archeozoic" is properly applied, rocks of that age should show 

 the earliest evidences of life. Certain beds of graphite; beds of 

 iron ore which were derived from carbonates; the not uncommon 

 occurrence of numerous flakes of graphite in certain Archean 

 schists, gneisses, and crystalline limestones; and the very existence 

 of the limestone itself, altogether quite certainly imply the exist- 

 ence of life in Archeozoic time. Limestone has sometimes been 

 of chemical origin, but the presence of clearly bedded graphitic 

 schists and crystalline limestones in a distinct sedimentary series 

 almost certainly shows the influence of organisms in the production 

 of both the graphite and the limestone. 



As to the character of the life nothing definite can be said, not 

 even whether it was plant or animal or both. Nothing like deter- 

 minable fossil forms have been found in Archean rocks, and even 

 if such ever were present they must have been obliterated by the 

 intense metamorphism to which the rocks have been subjected. 

 In the light of the evolution which took place during much better 

 known geologic time, it is quite certain that the Archeozoic or- 

 ganisms must have been much simpler forms than those of the 

 early Paleozoic which, in turn, were much simpler than those of 

 the present day. 



All we can say about Archeozoic climate is that, during some of 

 the time at least, it was favorable for the existence of life and for 

 ordinary geologic processes such as erosion and sedimentation. 



Economic Products. — Iron ore in workable beds occurs in the 

 Archean of the Lake Superior district. 



Granting the Archean age of the Grenville series, it contains 

 valuable marble deposits as at Gouverneur in northern New York. 



Granites intrusive into the Grenville contain rich magnetite 

 deposits in Essex county, New York. 



The cobalt and nickel deposits of Ontario, Canada, are, in 

 part at least, associated with Archean rocks. 



