42 H. B. KUMMEL 



noted by Andreae and Osann can be seen. Fragments of altered 

 shale can be found on the surface near the other intrusive trap 

 masses, but there are no extensive exposures of the rock in 

 place. Along the Palisade ridge the metamorphism is less pro- 

 nounced near its northern end in New York, and not infre- 

 quently beds in close proximity to the trap here show no signs of 

 alteration. Apparently, as the molten rock approached the 

 surface, its effect upon the adjacent beds was diminished. 



STRUCTURE 



Folds. — The general structure is that of a faulted monocline 

 the beds of which trend N. 20° to 50 E., and dip io° to 15 to 

 the northwestward. As a result of this, the layers to the north- 

 west, save where faulting has occurred, are above, and therefore 

 younger than the layers on the southeastern side. When exam- 

 ined more in detail, the structure is seen to depart locally from 

 a monocline. Several broad, gentle flexures occur, in addition 

 to a few sharply marked folds in the vicinity of the intrusive 

 traps and greater fault lines. A good example of the former is 

 seen in the shales of the Hunterdon plateau, where the beds are 

 so inclined that their outcropping edges describe a great curve, 

 parallel on the east, and southeast to the escarpment of the 

 plateau. The structure is a shallow syncline, whose axis is 

 inclined northwestward. Low folds occur in the valley of the 

 Raritan, particularly in the region north of Somerville. From 

 New Brunswick to Bound Brook the dip is quite uniformly to 

 the northwestward, averaging ten degrees, but further to the 

 west the monocline is interrupted by gentle flexures and swells 

 which are difficult to trace because of the absence of individual- 

 ity in the layers. The broad outcrop of the Brunswick shales in 

 the Raritan valley is due in large part to these low folds. 



More definite folds, all synclines, occur {a) near the Sand 

 Brook trap sheet, southwest of Flemington, [b) the New Ger- 

 mantown trap sheet, and (c) the'Watchung traps, whose great 

 crescentic curves are due to the synclinal structure of the inclos- 

 ing shales. Several examples of sharp folds occur near Glen- 



