ON THE LAKE SUPERIOR REGION 91 



Penokee- Gogebic, Rainy Lake, Lake of the Woods, and Thunder 

 Bay districts. Mr. J. U. Sebenius was with the party for the Mesabi 

 district, Mr. W. N. Merriam, for the Mesabi and Vermilion districts; 

 Mr. W. N. Smith, for the Thunder Bay district; Mr. E. D. Ingall 

 and Mr. T. D. Denis, for the Lake Huron district. The knowledge 

 of these men was of great assistance to the committee. 



In the following pages we shall give the successions and relations 

 of formations which we believe to obtain for each of the districts 

 visited, and give our opinion as to the major correlation of the rock 

 series of the various districts, so far as this can be safely done, and 

 the nomenclature which seems to best express the facts. 



For each district, unless otherwise specified, the succession will 

 be considered in descending order. In giving the successions for the 

 various districts, we shall use, for convenience, the names suggested 

 by geologists who have done the detailed work in the districts, without 

 .thereby expressing any opinion as to their appropriateness or their 

 advisability. 



In the Marquette district we found the upper series there exposed 

 to be as follows: (1) Michigamme slate and schist, and (2) Ishpeming 

 formation. Locally within the Michigamme slate, and apparently 

 near its base, is an iron-bearing horizon. The Clarksburg volcanics, 

 said to be a local phase of the Michigamme formation, were seen at 

 Champion. The basal member of the Ishpeming formation is the 

 Goodrich quartzite. This series, called the upper Marquette series 

 by the United States Geological Survey, has at its base a pronounced 

 unconformity, marked by extensive beds of conglomerate having 

 materials of diverse character. The dominant fragments of the con- 

 glomerate at the localities visited are from the Negaunee formation to 

 be mentioned below. The next series is the Middle Marquette series, 

 consisting of (1) the Negaunee formation, (2) the Siamo slate, and (3) 

 the Ajibik quartzite. In the publications of the United States Geo- 

 logical Survey this series was not separated from the series next 

 mentioned, but the work of Professor Seaman has shown that there 

 is a pronounced unconformity, marked by strong basal conglomerates 

 at the bottom of the Ajibik. Below this unconformity is the Lower 

 Marquette series, consisting of (1) the Wewe slate, (2) the Kona 

 dolomite, and (3) the Mesnard quartzite. At the places where we 



