SUMMARIES OF PRE-CAMBRIAN LITERATURE 

 OF NORTH AMERICA 



EDWARD STEIDTMANN 

 University of Wisconsin 



INTRODUCTORY 



In 191 5, summaries of pre-Cambrian literature from 1909 to 

 191 5 were published in the Journal of Geology. The summaries 

 published herewith bring this review nearly down to date. For 

 191 9, attention has been given only to those publications which 

 are likely to contain important papers on the pre-Cambrian. 

 Emphasis in these summaries is placed on stratigraphic facts and 

 problems. 



I. LAKE SUPERIOR REGION AND ISOLATED PRE-CAMBRIAN AREAS 

 OF THE MISSISSIPPI VALLEY 



In the Lake Superior region notable contributions to the 

 stratigraphy of the pre-Cambrian have been made by Wolff, Grout 

 and Broderick, Hotchkiss, and Allen and Barrett. The tendency 

 has been to subdivide the iron formations of the leading districts 

 into several units and to connect the occurrence of major ore 

 deposits with certain of these units. In the main productive 

 portion of the Mesabi district, Wolff from his extended experience 

 in drilling and mining has recognized four divisions of the Biwabik 

 iron formation. Grout and Broderick have recognized similar 

 units in the eastern, less-productive portion of the formation. 

 Hotchkiss has found an unconformity in the Ironwood iron forma- 

 tion of the Gogebic district and has recognized two units in the 

 upper division and three in the lower. He has also found an 

 unconformity between the iron formation and the overlying 

 Tyler slates. The recognition of these new unconformities, 

 Hotchkiss believes, does not call for a revision of correlation. 

 Allen has discovered an unconformity cutting the Upper Huronian 



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