SUMMARIES OF CURRENT NORTH AMERICAN PRE- 

 CAMBRIAN LITERATURE 1 



Boss 2 describes the dikes associated with the ore deposits of the 

 Gogebic iron range. They are dioritic and more or less altered; they 

 are approximately at right angles with the dip of the formation they 

 cut, and the greater number of them have an average easterly dip of 

 1 5° to 1 8° — sometimes they are folded in such a manner as to form 

 long synclinal basins with eastward pitch. In a majority of cases 

 mining exploitation has shown a succession of dikes, one below the 

 other, and ferruginous quartzite of varying thickness immediately 

 underlying each dike and forming the cap of the succeeding deposit 

 of ore. 



Comment. — The dikes have been shown by Irving and Van Hise 3 

 to be diabase, rather than diorite. With this exception, the above 

 observations are in accord with and confirm those of Irving* and Van 

 Hise in this area, and except in a few details nothing new is presented. 

 For a comprehensive discussion of the position of the dikes and their 

 relations to the ore bodies the reader is referred to Monograph XIX 

 of the United States Geological Survey. 



Wadsworth 4 describes the origin and mode of occurrence of the 

 Lake Superior copper deposits, and the age of the copper-bearing 

 series. A reexamination of the Douglass Houghton and Hungarian 

 River areas shows that the Eastern Sandstone passes under the lavas 

 with increasing dip, and that the junction is not a fault junction, but 

 that of a lava flow upon an underlying soft sand and mud. It is held 

 that the Eastern Sandstone is of Potsdam age, and underlies the copper- 

 bearing series, the first lava of that series having flowed out upon the 



1 Continued from p. 854, Vol. VI, Jour. Geol. 



2 Some dike features of the Gogebic iron range, by C. M. Boss, Trans. Am. Inst. 

 Min. Engineers, Vol. XXVII, 1898, pp. 556-563. 



3 The Penokee-Gogebic iron-bearing -series of Michigan and Wisconsin, by R. D- 

 Irving and C. R. Van Hise : Mon. U. S. Geol. Surv., No. XIX, 1892. 



4 The origin and mode of occurrence of the Lake Superior copper deposits, by 

 M. E. Wadsworth : Trans. Am. Inst. Min. Engineers, Vol. XXVII, 1898, pp. 669- 

 696. 



190 



