Lower Marquette Series in Michigan. 219 



contact of the lower iron bearing member with the upper 

 quartzite, when the ore may be either a concentration in the 

 lower iron-bearing member, or a detrital member of the upper 

 series, or (b) more rarely, entirely within the iron-bearing mem- 

 ber of the lower series. 



These descriptions are expressed briefly in the following 

 table, in which the members of the two series are shown in 

 parallel columns for lithological comparison. 



Menominee. Marquette. 



Michigam me Jasper. Jasper banded with ore. ) Iron 



Slates (Principal iron forma-) Magnetite-Actinolite >• forma- 

 tion.) Schist. ) tion. 

 Limestone. Quartzite. 

 Quartzite. 



Archaean. Archaean. 



It will be seen that the lithological resemblances are these : 

 (1) Each series has a similar quartzite at its base. (2) Each 

 contains iron-bearing formations. Neither is a safe basis for 

 correlation in the absence of direct stratigraphical evidence, 

 for not only has nearly every positive movement throughout 

 geological time been marked by a basal sandstone or quartzite, 

 but the undoubted general resemblance between the iron-bear- 

 ing formations of the two districts is not closer than that be- 

 tween either and like formations of Animikie age. 



On the other hand the lithological differences, and especially 

 the absence from the Marquette column of the Menominee 

 limestones and slates, are very striking. It is on this point 

 that recent work furnishes some positive, though not conclu- 

 sive evidence. 



Structure and Distribution. 



The Menominee rocks, as will appear in detail in a forth- 

 coming report, have been traced from Michigamme Mountain 

 with a north and south strike, north through T's 44 and 45 N., 

 R. 31 W. In these townships they lie, with an easterly dip, 

 on the eastern side of a structural axis, along which granite- 

 gneisses outcrop in the western part of T's 41 and 45 N., R. 

 31 W., and in the eastern part of T's 44 and 45 N., R. 32 W. 

 It has been possible to follow the Michigamme jasper care- 

 fully and closely by means of its magnetic properties. In the 

 middle of T. 45 1ST., R. 31 W., where the rock is next found 

 in exposures and explorations, it is seen to have somewhat 

 changed in character. The lower portion has become deci- 

 dedly quartzitic, containing, however, gashes and films of 

 specular hematite. The upper portion is finely banded, and 



