NEWARK ROCKS OF ROCKLAND COUNTY, N. Y. 



33 



Xorth of West Nyack the margin of the trap outcrop is more 

 irregular than at any other point along its entire length in both 

 New Jersey and New York. A spur of the ridge half a mile wide 

 juts out to the west for about a mile. At the northern and south- 

 ern ends of this spur there are smaller masses of trap, J 

 mile in length, which may be connected with the greater 

 mass, though separated from it by erosion depressions in the 

 bottom of which all rock outcrops are concealed by glacial drift 

 and alluvium (c, c, fig. 6). 



East of Valley Cottage (d, fig. 6) numerous bosses of fine grained 

 trap are exposed, in several of which masses of indurated, fine 

 grained sandstone are imbedded. Some of these inclusions have 

 a width of several feet. They are masses of the sandstone which 



Fig. 6 Map of the region near Nyack. 



were broken off and incorporated into the upper part of the trap 

 during its intrusion in a molten condition. Their occurrence is 

 conclusive proof of the intrusive origin of the sheet. 



From Valley Cottage the boundary extends a little north of 

 east, nearly parallel to the eastward bend of the basal margin at 



