428 THE r"ENOKEE IROlSr-BEARlKG SERIES. 



cleavage. Further, the great increase in thickuesi> in the central part of 

 the Eastern area might readily cause at the time of the ujjturning of the 

 series an increased pressure. That from this or some other cause these 

 rocks have been subjected to unusual pressure is shown by the foliated 

 character of some of tlie sericite-schists and the arrangement of tlie par- 

 ticles with their longer axes in a common direction in some of the quartzose 

 slates (pp. 4UG-408). To the east and Avest of the central portion of the 

 area, where the pressure has been less, no southern dips are found. 



There is one other possible explanation of the southern dips. The)' 

 may be regarded as overturns. Tlie dip of the Penokee series is usually 

 high, averaging from 60° to 70°. In the neighborhood of Tylers fork it 

 becomes very high, reaching from 70° to 80°, while at one place the slates 

 of the upper series are vertical, if not slightly inclined to the south. It 

 might readily be the case that the rai)id widening of the Eastern area 

 and the exceptional nature of the material, caused it to be overturned during 

 the time of its uplifting. Upon the whole, however, it is not so in'obable 

 that there has been an overturn as it is tliiit the southern dips are due to 

 slaty cleavage. The variations in dip are too wide and the change from 

 southern dips to northern dips too abruj)! to be satisfactorily explained by 

 an overturn. 



( )nr conclusion is, then, that the rocks of the Eastern area form, in all 

 probability, a continuous simple conformable succession from south to north, 

 which are the eastern extension of the main Penokee series. 



Sequence of events. — We are now prepared to give a brief histor^y of the 

 sreoloffy of the area and to correlate the belts here found with those to 

 the west. As in the main area, the complex of schists, gneisses, and 

 granites constitute a basement upon wliich the sedimentary rocks were 

 deposited. This basement Avas probablj' uneven, showing variation.s in 

 topography, as a consequence of which deposition began earlier in some 

 places than in others. The present occurrence of the belts is such as to 

 suggest that the eastern end of the area was higher than \\w western part 

 and did not recei\'e any deposits belonging to the lower foriuations. 



The exposures of the Quartz-slate member west of the Presque Isle are 

 so numerous as to leave no doubt as to the continuity of this belt. In the 



