ON THE LAKE SUPERIOR REGION 93 



of Bessemer, below the Keweenawan, the next formation is the great 

 Tyler slate formation of the Penokee series, while at Sunday Lake 

 the Keweenawan rests directly on the iron-bearing formation which 

 is stratigraphically below the slate. This relation led the party to 

 infer the existence of an important unconformity between the two. 

 The Penokee-Gogebic, or iron-bearing series, consists of (1) the 

 Tyler slate, (2) the Ironwood formation, and (3) the Palms slate. 

 This Palms slate was seen to rest directly upon granite south of the 

 Newport and Palms mine. At the former locality there is no con- 

 glomerate at the base. At the latter locality there is a conglomerate 

 at the base of the slate which, besides containing granite detritus, 

 also contains many cherty fragments supposed to be derived from 

 the next underlying sedimentary series. 



East of the Presque Isle River the lower sedimentary succession 

 of the Penokee-Gogebic district was visited, here consisting of (1) 

 cherty limestone and (2) quartzite. The quartzite dips to the north 

 at a moderate angle and rests upon green schist. The two forma- 

 tions were seen in direct contact for a hundred feet or more. The 

 cleavage of the green schist abuts against the bedding of the quartzite 

 at right angles. The quartzite near its base passes into a conglome- 

 rate, which, just above the contact becomes very coarse and con- 

 tains very numerous well- rolled fragments of the immediately sub- 

 jacent schist. The unconformity at the base of the quartzite could 

 not be more pronounced. 



The party nowhere saw the relations of the limestone-quartzite 

 series just described and the Penokee-Gogebic series -proper, but 

 they have no reason to doubt the conclusion of the United States 

 Geological Survey that the limestone-quartzite series is the inferior 

 one. 



The relations of the green schist, called Mareniscan by the United 

 States geologists, and the granite, which together constitute the base- 

 ment upon which the determined sedimentary series of the district 

 rest, were not studied by the party. The United States geologists 

 hold that the relations are perfectly clear, and that the granitic rocks 

 are intrusive in the green schist. 



In the Mesabi district the succession of the Mesabi series is as 

 follows: (1) Virginia slate, (2) the Biwabik iron formation, and (3) 



