EELATIONS OF THE GOODKICH QUAUTZITK. 411 



At Micliigamme tlie minor folding of the quai-tzite is beautifully shown. 

 (PI. XXX.) 



RELATIONS TO ADJACENT FORMATIONS. 



The details of the relations of the Goodrich (juartzite to the underly- 

 ing- Negaunee formation are so fully stated in connection Avith the latter 

 and the general geology that they need not be repeated here. Generally 

 stated, they are those of unconformity, the advancing sea having formed a 

 conglomerate at the base of the quartzite As a consequence of mining 

 development and the resistant character of this part of the formation, the 

 conglomerate may be seen at scores of localities lying upon and cutting 

 across the bedding of the underlying formation at a greater or less angle 

 (figs 20 and 21). 



Where erosion cut through the Negaunee formation the basal eon- 

 glomerate rests upon the Ajibik quartzite, and derives the majority of its 

 fragments from it. Where the latter formation is also cut through, as 

 apparently it is south of Palmer, the material is largely derived from the 

 Basement Com|)lex This fact, that the Goodrich quartzite thus comes in 

 contact not only with the Negaunee formation but with inferior formations, 

 shows that the unconformity between the Upper and Lower ]\Iarquette 

 series must be very considerable 



For much of the district, by a dj^ing out of the coarse fragmental 

 quartz and the appearance of clayey material the quartzite gradually passes 

 into the Micliigamme formation. This gradation is usually not rapid, and 

 hence the location of the boundary line between the two is somewhat arbi- 

 trary. At the western end of the district the quartzite is very thin, and the 

 formation passes quickly upward into the griinerite-magnetite-sehists of 

 the Bijiki horizon. (PI XXXI.) 



PETROGRAPHICAL CHARACTER. 



Macroscopicai. — A couglomerate is usually at the base of the Goodrich 

 quartzite. The character of the conglomerate depends upon the subjacent 

 formation, the larger portion of the detritus in each case being derived 

 from it. As has been stated, this inferior rock is usually the Negaunee 

 formation, and at the base of the Goodrich quartzite is ore, recomposed 

 ore, or ore, chert, jasper, and quartz conglomerate. At a few places the 

 subjacent rocks belong to the Archean, and at these the great variety of 



