THE NEWARK ROCKS 43 



more, southwest of Hopewell, and not far from the end of Rocky 

 Hill. Other instances were noted near the faults. 



In the area shown in Fig. 2, the Stockton and Lockatong 

 beds are the more constant in dip and strike, so that the raono- 

 clinal structure is most marked in these belts. The Brunswick 

 shales are characterized by shallow folds, some of them covering 

 an area of several square miles. These, combined with a fortu- 

 nate arrangement of faults, have greatly increased the area of 

 red shale outcrop, and so permitted the formation of the broad, 

 rolling lowland, so characteristic of the greater part of the New- 

 ark system. 



Within the area shown in Fig. 3, the extrusive trap sheets 

 are excellent guides in interpreting the structure, once their con- 

 formity to the shales has been completely demonstrated. The 

 curved outline of the Watchung Mountains is due to a gentle 

 synclinal fold, the westward side of which has been cut off by 

 a fault along the highland border of the formation. The high- 

 est beds of the Newark series are those along the axis of this 

 syncline. Between the Watchung Mountains and the Hudson 

 River the monoclinal structure prevails. This is also true of the 

 Newark beds of the New York area. 



Faults. — About seventy-five faults are known to occur, and 

 two of them, the Flemington and Hopewell faults, are of great 

 magnitude and extent, causing a repetition of all three divisions 

 of the Newark beds and involving dislocations equivalent to 

 a vertical movement of one half the entire thickness of the 

 series, perhaps 6000 or 7000 feet. Faults of such magnitude 

 must extend downward beyond the limits of the Newark rocks, 

 and involve the foundations on which they rest. Proofs of the 

 faulting are found (a) in the repetition of the strata, ($) crushed 

 and contorted strata, slicken-sided surfaces or overthrown dips 

 at every exposure along or near the fault line, (<r) diversity of 

 structure on opposite sides of the fractures, (d) contrasts in the 

 topography, and (e) the termination of ridges at the line of dis- 

 turbance. 



The northwestern border is formed in part by a series of 



