CONDITIONS FAVORABLE TO A BROAD TERRANE 147 



so generally interpreted as requiring that the Newark deposits be formed 

 in local basins. 



Conditions favorable to a broad Terrane 



There are, however, some considerations other than the occurrence of 

 marginal faults which favor the broad and continuous terrane hypoth- 

 esis. Five of them may be stated as follows : 



1. The several areas, with the exception of the Acadian area, are now 

 so nearly connected that if they were inclosed by a line which contin- 

 ued the outer margin of each to the nearer areas on either side, the 

 area included which was unoccupied by Newark deposits would about 

 equal that thus occupied. 



2. The remarkable resemblances observed to characterize near-lying 

 Newark areas and the rather marked differences noted between areas 

 widely separated indicate a distinct gradation in characteristics from 

 those peculiar to northeastern to those peculiar to southwestern areas. 

 These gradations are noted in the character of the deposits, in the nature 

 of the life remains, in the manifestations of volcanic activity, etcetera. 



3. The enormous degradation which all observers agree has taken 

 place since the deposition of the Newark sediments, favors the view that 

 the present areas are only remnants of a much larger area of deposits, 

 these remnants owing their preservation to their depression below the 

 baselevel of erosion and within the protecting walls of crystalline rocks. 



4. The community of structural peculiarities within the different 

 areas and the relations observed between the eastern and the western 

 areas of the sinuous double belt is not without significance. As early 

 pointed out by Russell,* the Connecticut valley and the northern por- 

 tion of the New York- Virginia area, as regards the sequence of their 

 deposits and the nature and the order of the included basalt layers, seem 

 to represent the opposite limbs of an imbricated fold, the parts of which 

 have been preserved by depression along fault planes within the crystal- 

 line rocks. Less noteworthy relationships are indicated in the prevail- 

 ing dips within the southern areas which lie to the east and those to the 

 west of an axial line (see figure 1). 



As the sinuous trend of this depressed double trough follows through- 

 out its extent the axis of Appalachian folding, it is easy to understand 



*I. C Russell : On the physical history of the Triassic formation in New Jersey and the Con- 

 necticut valley. Ann. N. Y. Acad. Sci., vol. i, 1879. 



XXII— Bull. Geol. Soc. Am.. Vol. 13, 1901 



