92 REPORT OF THE SPECIAL COMMITTEE 



saw the succession there is a belt of slate between the Kona dolomite 

 and the Mesnard quartzite of such thickness that it might possibly 

 be mapped as a formation if the exposures were more numerous. 

 The members of the United States Geological Survey think that 

 this slate is probably general for the district, as it shows wherever 

 the exposures are continuous from the dolomite to the quartzite. At 

 the base of the Lower Marquette series is an unconformity, marked 

 by conglomerates bearing fragments of all" the kinds of rocks seen in 

 the underlying series. Two classes of fragments are especially 

 abundant. These are (i) tuff, greenstone schist, and many kinds of 

 greenstones which belong to the so-called green-schist series of the 

 district, and (2) various kinds of granite and gneissoid granite. 

 Adjacent to the state road south of the city of Marquette the actual 

 contact was seen between the two series, the basal conglomerate 

 resting upon the green schist. The great variety of materials in this 

 conglomerate and the well-rounded character of the fragments left 

 no doubt in the minds of the members of the party that there is a 

 great structural break at the base of the Lower Marquette series. 



The lowest group of the Marquette district is a very complex 

 one, which has been designated as the Basement Complex. It con- 

 sists of two classes of material — the greenstone-schist series, and 

 the granites and gneissoid granites. The greenstone schist series 

 is especially well known through the description of the late George 

 H. Williams, found in Bulletin 62 of the United States Geological 

 Survey. This series is designated on the maps of the Marquette 

 Monograph as the Kitchi and Mona schists. Intrusive in the green 

 schist series are great masses of granite and gneissoid granite. No 

 evidence was seen by the party that any of the granites intrude the 

 sedimentary series above the green-schist series, although Seaman 

 thinks in one place a small mass of granite does intrude the Lower 

 Marquette series. It is believed that the great masses of granite of 

 the district antedate the three series here called Upper, Middle, and 

 Lower Marquette. 



In the Penokee- Gogebic district the highest rocks seen are the 

 Keweenawan traps and interbedded sandstones, the bedding of 

 which dips at a high angle to the north. No actual contact between 

 the Keweenawan and the next underlying series was seen, but north 



