456 THE CRYSTAL PALLS lEON-BEARING DISTRICT. 



nortliern part of the Fence River area into ferruginous quartzite at the- 

 base and griinerite-schist in the upper portion, it would seem probable that 

 the Groveland formation represents the underlying Ajibik quartzite as well 

 as the Negaunee formation of the western part of the Marquette range. 



This conclusion has an important bearing on the interpretation of the- 

 early geological history of what is now the Upper Peninsula of Michigan. 

 If the formations which constitute the whole of the Lower Marquette series 

 over the 25 miles or more of the productive and best-known portion of the 

 range are represented in the Menominee district aiid the intervening area 

 by a single formation, and that the highest in the Felch Moimtain succes- 

 sion — -namely, the Groveland formation — the formations below the Grove- 

 land formation are all older than the Marquette rocks and do not occur at 

 all within the productive portion of the Marquette range. Why are these 

 lower formations absent! 



To this question there seem to be two answers which are a priori 

 possible. It is conceivable that the quartzite, dolomite, and slates of the 

 south, or some of them, may have been deposited in a succession of 

 unbroken sheets over the whole Marquette area, in continuity with the simi- 

 lar Mesnard formations on the east, and that afterwards the main Marquette 

 area was elevated above the sea and entirely stripped of these formations 

 by long-continued denudation. Finally, when the time of deposition of 

 the Groveland formation came round, this elevated area had again been 

 reduced to sea level, and subsided below it, so that the Ajibik quartzite and 

 the Negaunee iron formation, and their southern equivalent, the Groveland 

 formation, were deposited in an unbroken sheet over the whole. If this 

 hypothesis is correct, two consequences should follow from it: First, we 

 ought to find some discordance between the Groveland formation or the 

 Lower Marquette quartzite and the lower formations in the marginal areas 

 between the Menominee and Marquette, and the Mesnard and Marquette 

 areas, respectively, or at least a gradual cutting out of these lower forma- 

 tions by the iron-bearing members and the lower quartzite, and, secondly, 

 we ought to find, in the lack of discordance, rocks present in the areas of 

 continuous deposition which represent the time of denudation. 



With regard to the first of these consequences no verification is possible, 

 at least in the tei'ritory between the Marquette and Fence River districts, 

 from lack of outcrops. Throughout the Northeastern area, from the north- 



