702 R. C. ALLEN AND L. P. BARRETT 



have not extended, it is clear that the main folding of the Animikie 

 on the east end is not only pre-Keweenawan but also pre-Copps. 

 The cause and the localization of the deformation are referable 

 to batholithic intrusion of granite. 



Relations to Keweenawan series. — Studies of the Keweenawan 

 series were limited to the problem of its relation to the Copps group. 



The Keweenawan is unquestionably unconformably super- 

 imposed on the Copps. The contact is marked in some places by 

 a strong basal conglomerate carrying pebbles and bowlders derived 

 from all of the members of the Copps and Animikie groups. Inas- 

 much as this conglomerate has not been described, perhaps a 

 brief reference to it will not be out of place here. In sections 14, 15, 

 and 16, T. 47 N., R. 43 W., the base of the Keweenawan is a 

 coarse, firmly cemented, sandstone 50 to 75 feet thick grading into 

 conglomerate near the base. The pebbles of the conglomerate 

 comprise fragments of vein quartz, red slate, quartzite, graywacke, 

 jasper, chert, and iron ore. 



Relations to Cambrian {Eastern or Jacobsville) sandstone. — • 

 The Eastern or Jacobsville sandstone has been described by other 

 writers as resting unconformably on rocks here designated as the 

 Copps group. This evidence rests on an examination many years 

 ago of exposures in test pits. These pits are now filled and over- 

 grown with brush and we were therefore unable to add anything 

 to existing information. 



RELATIVE TO THE BEARING OF CONCLUSIONS ON LAKE SUPERIOR 

 PRE-CAMBRIAN CORRELATIONS 



It is not our purpose to anticipate in this paper the following 

 discussion of the bearing of this revision of the geology of the 

 Gogebic Range on the more general problem of the pre-Cambrian 

 correlations. To the student of Lake Superior geology the sug- 

 gestion will arise that had these relationships been discerned 

 thirty years ago the history of the pre-Cambrian correlations 

 would probably have been markedly different, not only in Michi- 

 gan but in general. 



Any disposition which may be made of the Copps group in the 

 correlations must take into account the magnitude of the uncon- 



