364 THE PENOKEE IRON- BEARING SERIES. 



the last mentioned rock, there is here found several interlaminated belts of 

 fragmental and nonfragmental sediments at a horizon which, from its rela- 

 tions to the Quartz-slate member and the character of a portion of the 

 rocks contained, must be considered as belonging to the iron-bearing for- 

 mation. 



In the southern part of Sec. 20, T. 47 N., R. 43 W., Michigan, iron- 

 belt rocks occur over a distance of about one quarter of a mile north and 

 south. The first explorations were carried on in the extreme southern 

 part of the section. Here, resting upon a basic eruptive flow, is a con- 

 glomerate the mati'ix of which is largely nonfragmental. This peculiar 

 conglomerate is considered fully in another connection and need not at 

 present be noted further. Above this conglomerate there is within a few 

 paces of one another ankerite, chloritic and quartzose siderite, and actino- 

 litic quartz rock. This occuiTcnce well illustrates the mingling of frag- 

 mental and nonfragmental sediments, the quartz of the quartzose siderite 

 being fragmental. Also here, in striking juxtaposition, are unaltered car- 

 bonate and com))letely altered actinolitic slates. Other rows of test pits, 

 running north and south, extend for some distance east and west from 

 the east line of the section to three-quarters of a mile west of that 

 line. Each of these rows shows interlaminated layers of purely non- 

 fragmental sediments, which are typical feiTuginous cherts and mixed ores, 

 and layers of chloritic slates, which, while very fine grained, are in some 

 cases certainly partly fragmental, and are believed to be mainly a finely 

 divided mechanical sediment. A westward extension of this belt, as judged 

 by its course to the east (PI. xiii), would carry it through the extreme 

 south part of Sec. 19 and the north part of Sec. 30, T. 47 N., R. 43 W. 

 This expectation of a westwai'd extension of the belt is further indicated 

 by exposm-es of a westward continuation of the basic eru])tive flow found 

 in Sees. 18 and 20. The only outcrops of rock, however, which are here 

 known to occur cannot be referred to tlie Iron-bearing member, but nmst 

 be placed in the intermediate phase of rock referred to above, being 

 about one-half a fragmental and one-half a nonfragmental sediment. At 

 the exposures in the nortli part of Sec. 30 the mechanical sediment is ])re- 

 ponderant, wliile in the exposures in Sec. IS) the rock is a conglonu'rate 



