322 THE MARQUETTE IRON-BEARLNG DISTRICT. 



luinor faulting occurred. As a result, blocks of Negaunee jasper are found 

 in the o-ray wacke. At one place the lamination of the jasper abuts against 

 the bedding of the gray wacke. In sec. 35, T. 48 N., R. 27 W. (Atlas Sheet 

 XXVII), south of the west end of Teal Lake, the change is somewhat 

 abrupt. Here the top of the slate seems to have been a shear zone, and the 

 iron-stained slates are semicrystalline. Resting upon these, with scarcely 

 any gradation zone, are the iron-ore deposits. The above localities are the 

 best found for showing the ti-ansitioii zone between the Sianio slate and the 

 Ne<)-aunee iron formation. For most of the district exposures are not found 

 along the contact zone. 



THICKNESS. 



To give an estimate of the thickness of the underlying formations has 

 been difficult, and to determine the thickness of the Sianio slate is even 

 more difficult, because of its close minor plications. In the Ijnnid area of 

 Siamo slate in sees. 3, 4, 5, 8, and 9, T. 47 N., R. 26 W. (Atlas Sheets 

 XXXI and XXXIV), the folding is so complicated that it is impossible 

 to make any estimate of the thickness. The area perhaps most favorable 

 is that west and east of Teal Lake (Atlas Sheets XXVII and XXX), 

 where the belt has a width varying from a quarter of a mile to a half mile, 

 or even more. This great variation in width is undoubtedly due to minor 

 rolls in the formation, and taking the smallest width, 1,3U0 feet, with a dip 

 of 75°, we Avould have a thickness of about 1,250 feet. However, it is 

 known that slat}' cleavage and subordinate rolls are here develojied, so 

 that it is proliable that this thickness should be reduced liy one-half, and 

 perhaps by more. 



INTERESTING LOCALITIES. 



Michigamme area. — Beginning at tlie north and west, the first numerous 

 exposures of the Siamo slate are north of the Michigamrae mine, in sees. 

 19 and 20, T. 48 N., R. 30 W. (Atlas Sheet V), occupying for the most \rM-t 

 a vallev between the greenstone range and the granites. This is the 

 locaUty in which all of the mica-schists are found. As examined in the 

 field, they vary from a biotitic and chloritic quartz-schilst to a finely lami- 

 nated, chloritic biotite-schist which often contains large crystals of chlorite 

 and sometimes large crystals of hornblende. The rock, while distinctly 



