OUTLINE OF THIS PAPHR. 



The Penokee series proper is a successioTi of formations extending, with some 

 breaks, from hike Gojjebic, Michigan, to lake Nnmakagon, in Wisconsin, a distan<;e 

 of about 80 miles. It is a monoclinal series, its dips being- universally to the north. 

 The three formations making np the Penokee succession are tlie (Juartz-slate member, 

 the Iron-bearing member, and the Upper-slate member, and Ijelow these is the 

 Cherty limestone formation. The series is sharply separated geographically from a 

 crystalline complex to the south, called the Southern Complex. It is separated with 

 equal sharpness from the Keweenaw series to the north. 



Cha])ter 1 gives a history of the geological exi)lorations in the Penokee district 

 and a full sunimary of previous literature. 



Chapter II treats of the Southern Complex. This consists of two main types of 

 rocks — light colored, coarse grained granites and granite-gneisses, and dark colored, 

 fine grained, finely laminated schists. In passing from west to east are found in 

 order the Western granite, the Western green schist, the Central granite, the 

 Eastern green schist, and the Eastern granite areas. The rocljs of the iSouthern 

 Complex are always completely crystalline. If any of them are of fragmental origin 

 then' present constitution gives no evidence of this. The contacts betwi'en tlie granite 

 and the schists arc ernptive, the granite being the intrusive rock. The schists are 

 consequently older. Certain of the most laminated schists grade into rocks which 

 are of distinctly eruptive types, and hence the only rocks in the Southern Complex the 

 origiTi of which is known are igneous. 



Chapter III treats of the Cherty limestone below the I'euokee series proper. 

 This formation, instead of being continuous, is found only at intervals, and varies iu 

 thickness up to 300 feet. It consists of cherty dolomitic limestone alternating with 

 layers of chert. The Cherty limestone is a water-deposited sediment, but whether of 

 chemical or organic origin, or of botli, is uncertain. 



Chapter IV treats of the Quartz-slate member. This member rests directly upon 

 the Cherty limestone or upon the Southerii Complex. It is a persistent, well charac- 

 terized horizon, having an average thickness of about 500 feet. Tlie (Juartz-slate is 

 always plainly clastic, and quartz is its prominent constituent, altliough other 

 minerals, and especially feldspar, are not unimportant. Its uppermost horizon is a 

 layer of pure vitreous quartzite. 



MON XIX II XVII . 



