UNIVERSITY OF CALIFORNIA PUBLICATIONS 



BULLETIN OF THE DEPARTMENT OF 



GEOLOGY 



Vol. 10, No. 1, pp. 1-19 Issued April 27, 1916 



THE CORRELATION OF THE PRE-CAMBRIAN 

 ROCKS OF THE REGION OF THE 

 GREAT LAKES 



BY 



ANDEEW C. LAWSON 



CONTENTS 



PAGE 



Introduction 1 



Utility of Tentative Correlations 2 



Criteria of Pre-Cambrian Correlation 4 



Hypothesis of Two Periods of Granitic Invasion 5 



Application of the Hypothesis 6 



Northwest of Lake Superior 6 



South of Lake Superior 8 



North of Lake Huron 10 



Southeastern Ontario and Adirondacks 11 



Summary 12 



Events Connected with Granitic Invasion 12 



Departures from Unanimity 13 



Petrographical Discrimination of the Two Granites 15 



Subdivisions of Time — Nomenclature 16 



INTEODUCTION 



The meeting of the International Geological CongTess at Toronto 

 in 1913 seems to have marked a new epoch in the history of our ideas 

 of the pre-Cambrian of the region of the Great Lakes. The papers 

 which were presented at that meeting and which have appeared since 

 then, comprising new field observations extending from Rainy Lake to 

 the Adirondacks and embracing both sides of Lake Superior, not only 

 indicate a renewal of interest in the problems of pre-Cambrian geology, 



