CHAPTER y. 



THE NORTHEASTERN AREA AND THE RELATIONS BETWEEN 

 THE LOWER MARQUETTE AND LOWER MENOMINEE 

 SERIES. 



From the northernmost outcrops of the Fence River area to the north- 

 ern end of the Repubhc trough the air-Hne distance is about 1 1 miles. This 

 intervening territory, on one side of which we find the typical formations 

 of the Menominee district and on the other the typical formations of the 

 Marquette district, remains to be described in this chapter. It may con- 

 veniently be referred to as the Northeastern area. 



As was shown in the report on the Marquette district, in the pro- 

 ductive portion of the Marquette range between Negaunee on the east and 

 Republic on the west, the lower Marquette series consists of two or three 

 clearly marked formations, which, perhaps, may further be subdivided 

 according to individual taste.^ The lowest of these, the Ajibik^ quartzite, 

 which rests on the Archean complex, is fragmental in origin, and is prevail- 

 ingly a white vitreous quartzite, which in one or two localities is conglom- 

 eratic near the base. Often it is represented by a muscovite-schist as the 

 result of the dynamic metamorphism of the original arkose. In the eastern 

 part of the productive area of the Marquette district and along the northern 

 side of the main fold, in the western part of the district, this formation is 

 overlain by the Siamo slates.^ Elsewhere the slates are not present, or are 

 not known. 



The next formation is the Negaunee iron formation,* which has already 

 been referred to in Chapter II. This rock, which has many phases, as there 

 noted, is clearly marked off from the lower quartzite by its great richness 

 in iron and by the fact that over the whole Marquette district it nowhere 

 appears to contain fragmental material, except in the transitional zone 

 between it and the lower formations. 



' The Marquette iron-bearing series of Michigan, by C. E. Van Hise and W. S. Bayley, with a 

 chapter on the Republic trough, by H. L. Smyth: Hon. U. S. Geol. Survey, Vol. XXVIII, 1897, p. 221. 

 - Op. cit., pp. 528-529. ^ Op. cit., pp. 313-315. " Op. cit., pp. 328-407. 



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