conflicting Views of Lake /Superior Stratigraphy. 131 



Farther, the relative geographical positions of the Penokee, 

 the Upper Marquette and the Chippewa Quartzite districts are 

 such as to strongly suggest that they were once connected. 

 The Penokee Series at the east is cut off by the unconformably 

 overlying Eastern Sandstone; but east of the south end of 

 Gogebic Lake there are here and there outcrops of slate which 

 are like the Upper Slate Member of Penokee district, and a 

 short distance to the east the narrow belt spreads out into the 

 broad area of fragmental rocks of which the Marquette and 

 Menominee districts are arms. At the west the Penokee Series 

 has been entirely swept away by erosion, the copper-bearing 

 rocks coming in contact with the underlying gneisses and gran- 

 ites ; but to the south westward appears the fragmental quartz- 

 ites of the Chippewa valley which are believed to be its 

 continuation. 



The equivalency of the Penokee Series with the Animikie 

 is as plain as the equivalency of any two areas of detached 

 rocks in a single geological basin can possibly be in which is 

 lacking clear paleontological evidence. It has been seen that 

 above the Cherty Limestone of the Penokee Series is an 

 erosion interval. In the Animikie Series we know of no 

 equivalent to this member, and in what follows it is excluded 

 from the discussion. The Penokee and the Animikie rocks 

 have a parallelism in lithological characters which is most 

 remarkable. Not only is there a general likeness between the 

 specimens from the two districts, but almost every phase of 

 rock from the Animikie Series can be matched by specimens 

 from the Penokee district. In the Animikie district the for- 

 mations underlying the iron-bearing belt are not extensively 

 exposed, and consequently little is known of the Animikie 

 equivalent of the Quartz-Slate of the Penokee Series. But 

 along the Lower Current River, near Port Arthur, Ontario, 

 quartz-slates underlying the Iron-Bearing Member are found, 

 which resemble certain phases of the Penokee Quartz-Slate. 

 Beginning with the iron-formations, the parallelism between 

 the two series is almost exact. The irony beds upon Grunflint 

 Lake, where are found the best known exposures of the forma- 

 tion, are in their lower parts jasper, magnetite- actinolite-schist, 

 and cherty ferruginous rocks containing more or less iron car- 

 bonate. Higher up are thick layers of thinly bedded cherty 

 iron carbonate. All these varieties of rock are found in the 

 iron-formation of the Penokee Series, and at many places the 

 order of succession is the same. Above the iron- bearing belt 

 in both regions is a great thickness of fragmental clay-slates 

 and greywacke-slates which are again practically identical in 

 character in both districts. It is true that in the western part 



Am. Jour. Sci.— Third Series, Yol. XLI, No. 242.— February, 1891. 

 9 



