TITLES AND ABSTRACTS OF PAPPiRS 91 



posed. Moreover, it lias become evident that the wide-spread correlations 

 implied by the use of the same nomenclature nearly everywhere throughout 

 thisi great Precambrian province assumes much more with regard to the re- 

 gional succession in these ancient rocks than is actually known. 



Although it is not possible generally to demonstrate, with mathematical con- 

 clusiveness, that geological formations occurring in different localities are 

 equivalent, nevertheless the premature use of the same name for formations 

 the correlation of which is open to question, or the continued use of the same 

 name for formations after it has become evident that their correlation is in 

 doubt, is misleading, and an obstacle rather than an aid in geological investi- 

 gation. Hypothetical correlations of groups of rocks occurring in widely sepa- 

 rated districts may serve for comparison or as a stimulus to investigation, but 

 all the advantages of such tentative correlations may be attained by using a 

 general terminology ( Proterozoic, Archaeozoic, etcetera), and thereby avoiding 

 the definite correlations implied in the use of names of local origin. In the 

 Precambrian province which occupies the northern part of the Saint Lawrence 

 River basin there are four geographically and geologically separate subprov- 

 inces : (1) The region northwest of Lake Superior, (2) the region south of 

 Lake Superior, (8) the region extending northeastward from Lake Superior 

 and Lake Huron to Lake Timiskaming and Lake Mistassini, and (4) eastern 

 Ontario and the lower Saint Lawrence, with which might be included the 

 Adirondack region. With the possible exception of the south shore of Lake 

 Superior and the Lake Huron and Lake Timiskaming subprovinces, the evi- 

 •dence on which the rocks of these separate regions can be correlated is exceed- 

 ingly meager, and for the present, at least, the only logical course would seem 

 to be to build up a separate nomenclature in these various subprovinces by 

 using those names already defined in these localities, supplemented by such 

 local new names as becomes necessary from time to time as geological investi- 

 gation is continued. 



The wide-spread correlations implied in the use of a common nomenclature 

 throughout all the Precambrian subprovince of the Saint Lawrence basin has 

 been based on the assumption that the succession of formations within the 

 various subprovinces has been worked out to a practical completeness and on 

 the application of certain principles by which the correlation of the various 

 formations in these widely separated areas are presumed to be established. 

 The writer's purpose is to point out that the assumption that our knowledge 

 of the succession of formations in any of the subprovinces is complete is open 

 to question, and that the principles by which Precambrian rocks are generally 

 correlated are in part inapplicable and as a whole quite inadequate for the 

 establishment of a Precambrian nomenclature embracing all the territory in 

 the Saint Lawrence basin in which Precambrian rocks occur. 



Read in abstract from manuscript. 



Discussion 



Dr. A. P. Coleman: Doctor Wilson's paper is of importance as showing the 

 danger of extending a classification of the Precambrian worked out in one 

 region to other widely separated regions. His suggestion of more than two 

 ages of batholithic mountain-building lengthens out still farther the tremen- 



