436 THE PENOKEE IRON BEARING SERIES. 



Above the Quartz-f^late begins tlie uuuclastii' sediineiitatiun of the Iron- 

 bearing- iiieinber. The deposition of this beh did not go on undisturbed, 

 but alternated with clastic sediments;, and long before the whole of t! 

 iron-bearing member of the west was built up came the great volcanic 

 outbreak which resulted in piling uj) the series of flows, tuffs and inter- 

 stratitied elastics of the greenstone-conglomerate area. x\t or near the ces- 

 sation of volcanic activity the mingled clastic and nonclastic sediments 

 which overlie them began to form. At this time apparently the Iron-bearing 

 member < )f the western area had not yet wholly formed. Above the latter 

 followed probably fragmentals which were the equivalent of the Upper 

 slate member; but if this were the case they were wholh' or nearly AvhoUy 

 removed by erosion. After a long period of degradation began Keweenawan 

 time. Before the Eastern sandstone at the east end of the area was depos- 

 ited the three series of the district were tilted into their present inclined 

 position, and during this time and subse(p.iently underwent enormous 

 denudation. 



