4 



University of California Publications in Geology [Vol. 10 



CRITEEIA OF PRE-CAMBEIAN CORRELATION 

 The table which I offer for consideration is designed to be more 

 than an alternative to that of Allen and Barrett, in that it exemplifies 

 the application of a principle in the correlation of the pre-Cambrian, 

 which if true, should be of great interest and service to students in 

 this general field. 



The work of Allen and Barrett on the pre-Cambrian sequence and 

 structure of the Gogebic range is of a high order. These geologists 

 appear to have been actuated, however, by the principle, laid down 

 by Collins, of every man confining himself to his own bailiwick ; and 

 they do not discuss the relation of their own very important discoveries 

 to the general problem of the classification and correlation of the pre- 

 Cambrian. Yet, in the use of such terms as Huronian and Animikie 

 for major subdivisions of their sequence, they imply correlations and 

 conclusions which are at variance with the recent results of Collins 3 

 obtained on the north side of Lake Huron by methods quite as thorough 

 and reliable as their own. Indeed, it would be difficult to find a more 

 striking illustration of the infelicity of the exclusive method, of ignor- 

 ing what others are doing, than is afforded by a comparison of the use 

 of terms in the papers by Collins on the one hand and by Allen and 

 Barrett on the other. 



The correlation table here presented contains fifteen columns show- 

 ing the pre-Cambrian sequence in as many different districts dis- 

 tributed over the region of the Great Lakes from Rainy Lake to the 

 Adirondacks. The sequence in every district, with one exception, 

 column XI, is practically undisputed. The columns may be placed 

 side by side in various ways so as to suggest various correlations ac- 

 cording to the views of the correlator and the guiding principle of 

 correlation adopted by him. The difficulty of finding principles suffi- 

 ciently reliable to establish correlations in the pre-Cambrian is well 

 known. Those that have been used by geologists up to the present are 

 chiefly : ( 1 ) The principle of lithologic similarity and the community 

 of conditions of deposition inferred from this similarity. (2) The 

 principle of the similarity of sequence. (3) The principle of coinci- 

 dence of unconformities in the sequence. (4) The principle of irrup- 

 tive contacts. 



By diligent and repeated application of these principles numerous 

 attempts at correlation have been made, each one seeking to improve on 



3 The Huronian Formations of the Temiskaming Region, Canada, Geol. Sur- 

 vey of Canada, Mus. Bulls, nos. 8, 1914, and 22, 1916. 



