A CORRELATION OF THE PRE-CAMBRIAN FORMA- 

 TIONS OF NORTHERN ONTARIO 

 AND QUEBEC^ 



H. C. COOKE 



Geological Survey of Canada, Ottawa 



In a paper recently published in the Journal of Geology^ the 

 writer correlated the pre-Canibrian formations of northern Quebec 

 as well as facts obtained during the last ten years would permit. 

 The formations most satisfactorily correlated were a number of 

 scattered patches of sediments which had been given the local 

 names Pontiac, Mattagami, Broadback, and Brock series. In 

 composition, succession, structure, and external relations these 

 scattered patches of sediments were deemed sufficiently alike to 

 warrant substituting the general name Mattagami series for the 

 local names. The position of the Mattagami series in the geologic 

 column is shown in the following succession: 



Mistassini limestone Mattagami series 



Unconformity Unconformity 



Diabase dikes Gabbro and anorthosite 



Intrusive contact Intrusive contact 



Cobalt series . Granite-gneiss (around Lake 



Great unconformity St. John) 



Granite Intrusive contact 



Intrusive contact Nemenjish series (Grenville series ?) 



Lamprophyre dikes Abitibi volcanics (basalts, 



Intrusive contact andesites, rhyolites) 



During 1918 the writer had an opportunity to examine for the 

 first time the Timiskaming series in the Kirkland Lake district of 

 northern Ontario, and was so impressed by its similarity to the 

 Mattagami series that further opportunity was taken in 1919 to 

 investigate its relation to that series. The results indicate beyond any 



^ Published by permission of the Geological Survey of Canada. 

 " Journal of Geology, Vol. XXVII, Nos. 2, 3, 4, 5, 1919. 



304 



