744 6. Ke, INTE 
erate. Much of the material has been profoundly metamorphosed, 
and schist-conglomerates, mica-schists, and hornblende-schists have 
resulted. All of these rocks are cut by dikes and masses of green- 
stone. The formation is confined to the south central part of the 
district. ‘The volcanic material was poured out from the number of 
vents, the more important ones which have been recognized being 
located near Clarksburg, Greenwood, and Champion. ‘The formation 
grades into the Ishpeming formation or the Michigamme formation 
below, and into the Michigamme formation above. The Clarksburg 
formation belongs in age, either between the Goodrich quartzite and 
the Michigamme formation, or near the base of the latter. No 
estimate of the thickness can be given. 
The igneous rocks, other than those of the Clarksburg formation, 
are divided for convenience in discussion into two classes, in the first 
of which are placed those associated exclusively with the beds below 
the Clarksburg formation, and, in the other, those cutting also the 
beds above the Clarksburg. The rocks are all basic. The older rocks 
occur as dikes, bosses, sheets, and tuff beds, although the latter two 
are subordinate. The post-Clarksburg greenstones comprise only 
dikes and bosses. It is conjectured that these later greenstones may 
be the equivalents of some of the Keweenawan eruptives. 
Evidence of the unconformity between the Lower Marquette series 
and the Basement Complex is clear and abundant. At numerous 
places in the district the actual contacts of the basal conglomerate of 
the Marquette series and the Fundamental Complex may be seen. In 
all of these cases the detritus is most distinctly waterworn, and, while 
the major part of the material in each case has been derived from the 
immediately subjacent part of the Basement Complex, other material 
not occurring in the immediate neighborhood is found, thus showing 
conclusively that these rocks are not reibungs or fault breccias. There 
may be mentioned the principal localities at which contacts are well 
exposed. 
At the east end of the south side of the Marquette district there 
are several localities, from Lake Superior to west of Lake Mary, where 
a conglomerate is found bearing numerous bowlders of granite, gneiss 
and schist, identical with the rocks constituting the Basement Complex 
immediately adjacent. In Secs. 22 and 23, T 47 N, R 26 W, are two 
islands of the Basement Complex, about which are found magnificent 
exposures of great bowlder-conglomerate and recomposed granite, 
