442 Ilohbs — Geological Structure of the 



tion by Becker* and were extended and applied to the area in 

 the writer's report upon it.f The greatest value of the investi- 

 gation of this Newark area, as it relates to the structural 

 problems involved in the study of the crystalline belt, has 

 been to show that no adequate explanation can be offered for 

 the present attitudes of the rocks within that belt which fails 

 to take account of a deformation by normal faulting as well as 

 by folding, for it would be absurd to suppose that the faults 

 characteristic of the Newark areas are not extended beyond 

 their margin. Indeed, the evidence that they pass far beyond 

 these margins into the crystallines has been shown by their 

 direction of the courses of streams.;}; A somewhat careful 

 review of the studies made of the other Newark areas § of 

 the Piedmont plateau has shown that while systems of parallel 

 joints and faults had not been generally recognized as such, 

 with not an exception numerous intersecting faults of the nor- 

 mal type had in each area been observed, and all recent 

 observers have further expressed the view that many other 

 faults remained concealed. The obvious lesson from these 

 considerations is that the deformation of the intervening areas 

 of crystalline schists — and these areas are not large in propor- 

 tion to the Newark basins — must be not only by folding and 

 probably also by faulting in pre-Newark time, but there must 

 have been superimposed upon the earlier structures the system 

 of jointing and faulting of post-Newark time. It is probable 

 that the throws along the faults of this system outside the 

 Newark basins will in general not be as great as those within 

 the basins, for the reason that the latter are depressed areas 

 within the crystalline terrane, but it will hardly admit of doubt 

 that they have been important enough to produce a mosaic of 

 orographic blocks in which different beds will be placed in 

 juxtaposition along essentially vertical walls at the present sur- 

 face. Another result of the study of the Newark areas has 

 been to confirm the views of some writers that displacements 

 are seldom concentrated upon a single plane of faulting but 

 are usually distributed over a number of parallel planes lying 

 in a zone more or less extended. Such distributive faulting 

 renders more difficult the observation of individual fault planes, 

 and even when these are discovered it is apt to leave an erro- 

 neous impression of their relative importance. 



* George F. Becker, Finite homogeneous strain, now and rupture of rocks ; 

 Bull. Geol. Soc. Am., iv, 50, 1893. 



f The Newark system of the Pomperaug valley, Connecticut, Twenty-first 

 Annual Report of the Director of the U. S. Geological Survey, Part III, pp. 

 1-160. 



{The river system of Connecticut ; Jour. Geol., ix, pp. 469-484 (1901). 



§ On the former extent of the Newark system ; Bull. Geol. Soc. Am., xiii, 

 pp. 139-148, 1902. 



