712 C. K. LEITH AND R. C. ALLEN 



level of the Hemlock and Michigan mines the folds in the iron 

 formation are truncated by a heavy conglomerate and quartzite 

 carrying fragments of the Negaunee formation of all sizes up to 

 several feet in diameter, including small, angular, hard jasper frag- 

 ments, rounded pebbles of chert and ore, and great bowlders of 

 the iron formation. It is reported that this same conglomerate 

 was found by drilling in similar relations to the iron formation 

 about three miles south of Amasa and in section 36, T. 44 N., 

 R- 33 W., about four miles farther southward. There can be no 

 reasonable doubt that this conglomerate-quartzite is the Goodrich 

 formation of the Marquette Range, where exactly similar relations 

 are observed. 



The productive iron formation at the Hemlock mine extends 

 with only a few unexplored breaks in drift-covered country south- 

 eastward around the great anticline of Hemlock volcanics and other 

 rocks and is believed to be almost if not quite continuous with the 

 iron formation passing through the Hollister, Armenia, and other 

 mines in the vicinity of Crystal Falls. Such continuity is indicated, 

 so far as definite information is available, by drilling, underground 

 openings, and magnetic surveys. Furthermore, the iron formation 

 on the west and southwest sides of the great Crystal Falls oval 

 anticHne maintains the same position with reference to the under- 

 lying Hemlock volcanics that it does on the north and east sides. 

 Therefore if the iron formation at the Red Rock and Hemlock 

 mines is Negaunee, the burden of proof rests on those who would 

 assert in the absence of any supporting facts that the Upper-Middle 

 Huronian unconformity cuts out the Negaunee iron formation and 

 occupies an inferior position with reference to the Vulcan iron forma- 

 tion at any or all points southward. This practical continuity was 

 accepted by Clements in 1899 and by Leith and Van Hise in 191 1, 

 as shown on the maps issued in Monographs j6 and j2 of the 

 United States Geological Survey. In fact, Leith and Van Hise 

 argue in this work that the iron formation at the Hemlock 

 mine is not Negaunee on the assumption of practical continuity 

 with the Vulcan formation of the Crystal Falls district to the south 

 and lack of continuity with the Negaunee formation a few miles 

 northward. 



