SOUDAN FORMATION. 201 



formation rocks which immediately underlie them, and in places are seen 

 in juxtaposition with the conglomerate. Erosion has removed the con- 

 glomerate in some- cases, leaving small areas of the jasper only a few 

 yards in extent surrounded by the conglomerate. Associated with the 

 jasper at this place are very narrow bands of black graphitic slate. It 

 is from some of these bands that the fragments of slate in the overlying 

 conglomerate have been derived. There is an area about 100 yards 

 wide on the slope of this hill in which the conglomerate and underlying 

 jasper are intimately associated. North of these exposures occur the 

 iron-formation rocks, consisting of jasper, cherts, and iron ore interbanded 

 and closely infolded with the green schists. The iron formation has its 

 normal characters, which have already been described. The green 

 schist associated with it possesses an exceedingly well-developed fissility, 

 which strikes N. 70° E. The schist is much crumpled in places and 

 shows minor faulting, with bending of the lines of schistosity. The 

 faults cut across the schistosity at an angle of 45° and extend about 

 northwest-southeast. This schist is impregnated in areas of irregular 

 outline with iron, especially along the southern side of the exposures 

 nearest the jasper. A great deal of vein quartz has also been infiltrated 

 into the schist and is found in thin sheets marking the planes of schistosity, 

 and also in fine systems of rectangular veins which cut the schistosity. 

 The green schist and iron formation are most intimately infolded, forming 

 a series of anticlines and synclines having very steep pitches. The axes of 

 the folds have a strike approximately coinciding- with the strike of the 

 schistosity in the green schists, N. 70° E., showing an exceedingly close 

 folding of the rocks. A great number of these small folds was observed, 

 and in some cases the bands of iron formation or of schist could be traced 

 through several folds. It is very clear that the close infolding here has 

 produced a kind of fluted structure which is best developed on the saddle 

 connecting Tower and Lee hills, which stand en Echelon to each other from 

 northwest to southeast. 



The same kinds of intricate plications of jasper and green schist can 

 be seen on the numerous exposures on Soudan Hill. An especially good 

 one occurs on the north flank of the hill about 1,040 paces north, 330 paces 

 west of the southeast corner of sec. 28, T. 62 N., R. 15 W. Numerous 

 other cases may be observed west of the Montana pit and on the north 



