XXII OUTLINE OF THIS M0N0(;RAPH. 



The Southern Complex is treated under the divisions micaceous schists, amphibole-schists, gneiss- 

 oid granites, Palmer gneiss, and intrusives. The micaceous schists include muscovite-schists, hiotite- 

 schists, feldspathic biotite-schists, and hornbleudio biotite-schists. The amphibole-schists include 

 greenstone schists, hornblende-schists, and micaceous hornblende-schists. The intrusives are mainly 

 basic and acid dikes. The greeenstone schists, the granites, and the dike materials are similar to the 

 corresponding rocks of the Northern Complex. The granites are intrusive in the schists. The isolated 

 areas within the Algonkian are gneissoid granite and schistose greenstones, that differ in no essential 

 respect from the corresponding rocks of the Northern Complex and Southern Complex, The Base- 

 ment Complex was deeply denuded before Lower Marquette time, as is shown by the fact that the 

 plutonic rocks yielded their detritus to the basal formation of the sedimentary series. 



Chapter III treats of the Lower Marquette series. The Lower Marquette .=eries is composed of 

 the following formations, from the base upward : The Mesnard quartzite, the Kona dolomite, the Wewe 

 slate, the Ajibik quartzite, the Siamo slate, and the Negaunee iron formation. For each of these 

 formations the distribution, exposures, topography, folding, petrographical character, relations to 

 adjacent formations, thickness, and interesting localities are discussed. In treating the Negaunee 

 iron formation, the iron-ore deposits and prospecting are also considered. 



The Mesnard quartzite fdimation, from 110 to 670 feet thick, is, as the name indicates, chiefly a 

 metamorphosed sandstone. However, in this formation are other varieties of rock. At the bottom 

 is a conglomerate, which at most places, in grading into the quartzite, passes through slate and 

 graywacke. The conglomerate is basal, in any particular locality being composed of coarse and fine 

 detritus from the immedi.itely adjacent rocks of the Basement Complex. At the top of the formation 

 is a thin belt of slate. The Mesnard quartzite is the first deposit of the transgressing Lower Mar- 

 quette sea. By the time the sea had transgressed a short distance upon the Marquette district the 

 Kona dolomite began to be formed, and hence the Mesnard formation is confined to the eastern part 

 of the district. In a large way the Mesnard ibrmation is folded into an east-west syncline with a 

 westward pitch. The two limbs unite south of Marquette and complete a L). Superimposed upon 

 this fold of the first order are close folds of higher orders, running in various directions, but more 

 continuously east- west. The rocks of the formation vary from those which have been indurated 

 mainly by siliceous cementation to those which have been completely metamorphosed. At various 

 places along the contact horizon of the Marquette series and the Basement Complex the mashing and 

 shearing have been so profound as to transform both into crystalline schists, which appear to grade 

 into each other. The coarser-grained kinds of the dynamically metamorphosed rocks are extensively 

 fractured, while the finer-grained kinds are mashed without macroscopioal fractures. Microscopically, 

 every original particle, small or large, shows strain effects. 



The Kona dolomite, from 425 to 1,373 feet thick, is largely an altered limestone. The formation, 

 however, includes interstratified layers of slate, graywacke, and i|uartzite, with gradation phases 

 between these and the pure dolomite. The Kona dolomite, like the Mesnard quartzite, is confined to 

 the eastern part of the district. The formation has been folded iu a complex manner, the folds running 

 east-west and north-south. Consequent upon the folding and the different resisting powers of its 

 layers, the topography of the formation is exceedingly rough. When deformed the dolomite yielded 

 in most places without prominent fractures or cleavage, but iu the interstratified slates cleavage 

 was developed in many places, and the graywackes and quartzites were fractured or brecciated. 

 The dolomite varies through a slate into the Mesnard quartzite below, and by a lessening of the 

 calcareous constituent gradually passes into the Wewe slate above. 



The Wewe slate, 550 to 1,0,50 feet thick, is chiefly a metamorphosed mudstone. With the slates 

 are, however, conglomerates, quartzites, graywackes, mica-slates, and mica-schists. The Wewe slate, 

 like the two previous formations, is confined to the eastern part of the district. The formation in a 



