462 THE MAKQUETTE IRON-BEARING DISTRICT. 



sec. 18, T. 47 N., R. 27 W. (Atlas Sheet XXV), for instance, the volcanic 

 conglomerates are iii contact with graywackes or with arenaceous slates. 

 The exact locality of the contact in question is the east end of the top of 

 the hills north of Stoneville station. The Clarksburg rocks at this place 

 consist principally of conglomerates with a green schistose matrix and 

 of tuffs. The pebbles of these conglomerates are fine-grained diabases, 

 quai-tzites, slates, and granites. The south side of the hill, which is 

 composed principally of the greenstone-conglomerates, is faced with the 

 graywackes, which, near the top of the hill, appear to be beneath the con- 

 glomerates unconformably. At the east end of the hill again are other 

 arenaceous slates, and these apparently strike directly into the hill. Here 

 the volcanics again appear unconformably upon the graywackes. 



A little farther west, however, near the center of sec. 13, T. 47 N., 

 R. 28 W. (Atlas Sheet XXV), at the base of the large hills on the north side 

 of the railroad track, are graywackes like those in sec. 18, but at this place 

 they seem to grade up into tuffs, which are interbedded with the greenstone- 

 conglomerates. At many other localities the same relations are observed 

 between tuffaceous and lava beds and graywackes. The latter are inter- 

 leaved with the former, and are much more abundant among the lower beds 

 than among the higher ones of the formation. 



On its northern side the belt of Clarksburg rocks is everywhere bor- 

 dered by the Michigamme slate, the relations between the two formations 

 being very similar to those between the volcanic formation and the forma- 

 tions to the south. At Clarksburg (Atlas Sheet XIX) these relations are 

 plainly seen. In the little dome-like hill north of the raih-oad track and 

 east of the station sedimentary, graywacke-like beds and conglomeratic 

 greenstones are regularly interbedded. On the hills northwest of the A'illage 

 ai"e slaty, tuffaceous rocks, in which the included fragments become smaller 

 and smaller as we pass northward into the Michigamme slates, until at a 

 short distance northward typical slates are met with. No sharp line of 

 demarcation between the tuffs and the slates can be detected, the former 

 apparently grading into the latter by a gradual diminution in the amount 

 of tuffaceous material intermiBgled with the sedimentary substance. 



