462 THE CRYSTAL FALLS IRON-BEARING DISTRICT. 



stated, the granites and schists extend southward to the Felch Mountain 

 fragmentals, and here they are unconformably beneath the latter. Moreover, 

 since the Sturgeon River rocks and the lower members of the Felch Moiin- 

 tain series are identical in character, it is probable that they are of the 

 same age, in which case the granites and schists that are older than the 

 Felch Mountain rocks are older also than those of the Sturgeon River 

 tongue. 



The relations of the sedimentary series to the granites on the north 

 have not been determined, because no contacts are exposed. The granites, 

 however, can be traced northward until they are found unconformably 

 beneath the rocks of the Lower Marquette series at Republic, and these, so 

 far as is known, are the oldest sediments in Upper Michigan. There can 

 be little doubt, therefore, that the relations of the sediments to the northern 

 granites are the same as those with the southern schist complex. 



The granites of the two areas surrounded by the sediments are prob- 

 ably of the same age as the northern and southern granites. The rocks of 

 the area in sees. 7 and 8, T. 42 N., R. 28 W., and sec. 12, T. 42 N., R. 29 W., 

 are demonstrably beneath the conglomerates, though their relations with the 

 dolomites have not been determined. A well-marked contact between the 

 granites and the conglomerates is exposed at the south base of a small hill 

 of granite in the NE. J sec. 7, T. 42 N., R. 28 W} The conglomerate here 

 is well bedded. Its strike is N. 60° W., and its dip almost vertical. It 

 consists largely of pebbles and bowlders of granite identical with the granite 

 composing the hill, and a matrix constituted entirely of granitic debris. 

 The contact, though exposed for only a short distance, seems to be an 

 erosive one. It is certainly not an igneous one. 



From a consideration of the facts as given above, there can be little 

 doubt that the rocks of the granitic areas within the Sturgeon River tongue 

 and of those bounding it on the northern and the southern sides are older 

 than the sediments within the tongue, though this has not been proved for 

 the granites with respect to the limestones. 



From the lithological similarity of the Sturgeon River fragmentals 

 with those of the Felch Mountain district, and from the structural relations 

 exisiting between the rocks of the two districts, it is practically certain that 

 the Stursreon River sediments are of the same a^e as the Felch Mountain 



' The exact location of the coutact is 400 paces N., 280 W., of the southeast corner of section 7. 



