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National Geographic Magazine. 



sinking, the adjacent areas were rising, in order to furnish a con- 

 tinual supply of material ; the occurrence of heavy conglomerates 

 along the mai'gins of the Newark formation confirms this suppo- 

 sition, and the heavy breccias near Reading indicate the occur- 

 rence of a strong topography and a strong transporting agent to 

 the northwest of this part of the Newark belt. It will be neces- 

 sary, when the development of the ancestors of our present rivers 

 is taken up, to consider the effects of the depression that 

 determined the locus of Newark deposition and of the adjacent 

 elevation that maintained a supply of material. 



10. Jurassic tilting. — Newark deposition was stopped by a 

 gradual reversal of the conditions that introduced it. The 

 depression of the Newark belt was after a time reversed into 

 elevation, accompanied by a peculiar tilting, and again the waste 

 of the region was carried away to some unknown resting place. 

 This disturbance, which may be regarded as a revival of the 

 Permian activity, culminated in Jurassic, or at least in post- 

 Newark time, and resulted in the production of the singular 

 monoclinal attitude of the formation ; and as far as I can cor- 

 relate it with the accompanying change in the underlying struc- 

 tures, it involved there an over-pushing of the closed folds of the 

 Archean and Paleozoic rocks. This is illustrated in figs. 2 and 3, 



Fia. 2. 



Fig. 3. 



in which the original and disturbed attitudes of the Newark and 

 the undei-lying formations are roughly shown, the over-pushing 

 of the fundamental folds causing the monoclinal and probably 

 faulted structure in the overlying beds.* If this be true, we 

 might suspect that the unsymmetrical attitude of the Appalachian 

 folds, noted by Rogers as a characteristic of the range, is a 

 feature that was intensified if not originated in Jurassic and not 

 in Permian time. 



* Amer. Journ. Science, xxxii, 1886, 343 ; and Seventh Ann. Rept. 

 U. S. Geol. Survey, 1888, 486. 



