Lower Marquette Series in Michigan. 217 



Marquette District. Menominee District. 



Upper Marquette. Upper Menominee. 



Unconformity. Unconformity. 



Lower Marquette. Lower Menominee. 



Unconformity. Unconformity. 



Archaean. Archaean. 



This undoubtedly constitutes a strong chain. The weak 

 point as Yan Hise has fully recognized is that neither of the 

 sedimentary series of the one district has been traced into the 

 corresponding series of the other. Consequently to correlate 

 the two series of the one with the two series of the other, 

 involves the assumption that the two time-breaks extend over 

 both districts, and mean the same thing in each. 



Lithological Characteristics. 



Before considering the lithological similarities of the indi- 

 vidual formations, it is first necessary briefly to recall the 

 characteristics of, and the order of succession in, the lower 

 series of the two districts. 



Lower Menominee. 



Avoiding minute subdivision the lower Menominee consists 

 of 



(1) A basal quartzite, rarely conglomeratic. The thickness 

 may reach a maximum of about 1000 feet, and over large 

 areas is at least 700 feet. 



(2) A crystalline limestone which averages about 700-1000 

 feet in thickness. On the Fence River in T's 44 and 45 1ST. R. 

 31 "W"., where it largely if not entirely replaces the lower 

 quartzite, the thickness attained, if there are no subordinate 

 folds, is from 1500-2000 feet. 



(3) Red, black and green slates, that are not known to ex- 

 ceed 200-300 feet in thickness. The slates here and there con- 

 tain the iron formation that affords the rich ores of Iron 

 Mountain and Norway. In th'e southern part of T. 44 N., R. 

 31 "W., the horizon of the slates is in part occupied by 

 altered eruptives, that rapidly increase in thickness towards 

 the north, the whole attaining a maximum of nearly 2000 feet 

 on the Fence River in T. 45^K, R. 31 W. 



(4) The highest member, except volcanics, yet recognized in 

 the Felch Mountain and Fence River divisions of the Lower 

 Menominee is typically developed at Michigamme Mountain, 

 S. 4, T. 43 N., R. 31 W. and S. 33, T. 44 1ST., R. 31 W., and has 

 been called the Michigamme jasper. This is a greatly altered 

 ferruginous rock usually carrying apparently fragmental quartz 

 grains. Various stages in the alteration permit two or three 



