BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 4, pp. 333-348 August 4, 1893 



THE ARCHEAN ROCKS WEST OF LAKE SUPERIOR* 



BY WILLIAM HENRY CHATTERTON SMITH 



(Read before the Society December 30, 1892) 



CONTENTS 



Page 



The Nomenclature adopted 334 



The Region studied 334 



Its Boundaries 334 



Geologically complex 334 



Its topographic Character ' 334 



Present Status of the Investigations 335 



Distribution and Relation of the Rocks 335 



Two great Divisions and their Extent 335 



Lower Archean Series 335 



Upper Archean Series 336 



Terms Contch idling and Keewatin Series suggested by Dr Lawson 330 



Character and field Relations of the Laurentian Rocks 336 



Relation of Contchiching and Keewatin Series to Laurentian Granites. . . 337 



Contact Phenomena Criterion of Relative Age 337 



Character of the Contact 338 



Origin of the Laurentian Rocks 338 



Laurentian Rocks the younger 338 



Selection of the Term Laurentian based on imperfect Knowledge. . . . 338 



Considerations affecting the Status of the Term Laurentian 339 



The Contchiching Series 340 



Rocks composing it 340 



Position and Relation of its Rocks 340 



Its Thickness 340 



Clastic in Origin 341 



Structural Conformity between Contchiching and Keewatin 341 



The Contchiching and Keewatin lithologically distinct 341 



Conditions under which Contchiching and Keewatin wei'e formed 342 



The Keewatin Series 342 



Rocks composing it 342 



Its stratigraphic Succession 342 



The Steep Rock Series 344 



Discordant in Character 344 



Its Stratigraphy 344 



* Published by permission of the Director of the Canadian Geological Survey. 

 L— Bull. Geol. Soc. Am., Vol. 4, 1892. (333) 



