NEWARK ROCKS OF ROCKLAND COUNTY, N. Y. 



41 



and that it has been worn down to a much lower level in the gap 

 than on either side. Branches of Minisceongo creek drain north- 

 ward through this gap. Data are at hand to show that a wide 

 and deep, drift-encumbered valley extends south from the gap 

 for several miles in the sandstone, and also northward toward 

 the village of Thiells. No exposures of rock were found along 

 it, even where the streams have cut deep gorges in the drift. 

 Thus it is entirely within the bounds of possibility that the trap 

 of the Palisades ridge which is last seen in the railroad cut 400 

 yards south of Mt Joy station underlies the swamp to the west 

 and is connected with the trap area near Ladentown. 



The Ladentown trap is very fine grained, more so than that 

 of the Palisades ridge. It is moreover frequently vescicular and 

 shows some evidence of a ropy structure, characteristics which 

 are nowhere known to occur along the Palisades sheet, but which 



Fig. 9 Sketch map showing relations of trap and sedimentary beds near Ladentown. 



are of frequent occurrence along those sheets of New Jersey which 

 have been proved to be surface flows. The evidence is not con- 

 clusive, but the data suggest that the trap of the Ladentown area 

 reached the surface and overflowed. 1 This conclusion is not in- 



1N. H. Darton was the first to my knowledge to make this suggestion. 



