38 H. B. KUMMEL 



son River, were it not that it ascends by irregular steps to higher 

 horizons. West of Haverstraw it trends nearly at right angles 

 to the strata, and is more like a dike than an intrusive sheet. A 

 small area near Ladentown, which may be the western extension of 

 the Palisades, presents some characteristics of an overflow sheet, 

 indicating that possibly the trap here reached the surface. The 

 adjacent sediments have often been greatly metamorphosed. So 

 intense has been this alteration that at distances, often of 100 

 feet the rocks are as completely "baked" as those immediately 

 adjoining the trap. Measured along the surface, traces of meta- 

 morphism are frequently found one foot from the nearest trap 

 outcrop. The complete absence of scoriaceous rock, of amyg- 

 dules, of the vesicular, or the rolling-flow structure, is negative 

 evidence of their intrusive origin which must not be neglected. 

 Moreover, masses of shale and sandstone have been imbedded 

 in the trap near both the under and upper surfaces, and the trap 

 itself shows evidence in its texture of having cooled more 

 slowly (and therefore presumably at greater depths) than the 

 overflow sheets. 



Plugs. — Round Mountain, a circular mass of trap, south of 

 Cushetunk Mountain, suggests by its shape, that it is an irruptive 

 plug or stock, but in the absence of positive evidence as to its 

 relations to the surrounding metamorphosed shales, no final 

 statement is warranted. 



Dikes. — The positions of the principal dikes are represented 

 on the accompanying maps. A few others are known, but are 

 too small to show on a map of this scale. Locally the adjoining 

 shales are slightly metamorphosed. 



The age of the trap rock. — The overflow sheets are contempo- 

 raneous with the beds between which they lie, i. e., the upper 

 third of the Brunswick shales. 



The intrusive masses extend, for the most part, well up into 

 the Brunswick shales, and are therefore younger than these. 

 Moreover, so far as the evidence goes, they antedate the dis- 

 turbances which closed the deposition of the Newark beds. 

 There are good reasons for believing that many, perhaps all, of 



