40 THE PENOKEE IRON-BEARING SERIES. 



defined dip of 77° to the south, and strike of north, 75° west. In following the strike 

 west, one passes within 25 feet of the outcrop of siliceous marble which has a northerly 

 dip. Between 100 and 200 feet south, on the line of the railroad, other large expo- 

 sures of gneissoid granite arc found having essentially the same bedding as that men- 

 tioned above. When the railroad cut is completed at this locality the absolute junc 

 tion of the Laurentian and overlying Huronian will doubtless be exposed. There can 

 be no doubt of the unconformability of these forniatio'is, approaching each other as 

 they do with a persistent opposite dip and somewhat dirterent strike. Unconforma- 

 bility has been shown to exist between the Laurentian and Hui'onian in Michigan, 

 but this is the first time that it has been proved in Wisconsin. Northward from the 

 granites the section has been completed for over 1,000 feet. In this space are included 

 two "magnetic ore" beds, the southern I'M and the northern over 500 feet thick. 

 Directly above or north from the northern " ore " bed there is a space of 1,400 feet ui)on 

 which exposures have not been found. Above this blank recent railroad excavations 

 enabled Mr. Wright and myself to subdivide and extend the belt of 400 feet, supposed 

 to be the uppermost member of the Penokie system, into: «, siliceous schists, 100 

 feet; b, blank (Bad river), 75 feet; c, contorted black slate, 250 feet; d, diorites, 75 

 feet; and e, black porphyritic slates, 50 feet. 



Owing to the heavy deposits of drift we were unable to find exposures for 1,300 

 feet north from the black porphyritic slates. 



We then found what are probably the latest beds of the Huronian formation : g, 

 black slate, 40 feet; /(, quartzite, about 250 feet; i, slaty amygdaloid, 7~> feet. 



The thickness of the formation I estimate at something over 5,000 feet. The 

 dip is about 66° to the north, showing entire conformability throughout. (Pp. 42-44.) 



18T7. 



Irving (R. D.). Report of Prof. Irving. In Annual Report of Progress and Re- 

 sults of the Wisconsin Geological Survey for the year 1876, by T. V. Ghamberlin, 

 pp. 13-18. 



This report contains a brief account of the progress of the work under 



R. D. Irving in northern Wisconsin, but nothing' tliat is not much more 



fully developed in the third volume of tlie Geolog-}' of Wisconsin, published 



in 1.S80. 



Weight (O. E.). Mr. Wright's report. In same publication as the preceding, 

 pp. 18-23. 



Contains a brief preliminary statement of results obtained in the 

 Penokee region in 187G. The same results are given mf)re fully by Mr. 

 Wright in the third volume of the Geology of Wisconsin. We may merely 

 quote the following generalization : 



