THE NEWARK ROCKS 31 



bedding of the sandstones, and represents a constant horizon. 

 This being the case it gives us a reliable datum line. The posi- 

 tion of the sandstones near Newark and vicinity in reference to 

 the trap agrees with that of the Brunswick shales further south, 

 and not with that of the Stockton sandstones. Second, they 

 are too far removed from the base of the series, which follows 

 the Hudson River, to be classed with the Stockton beds. 

 Thirdly, when traced southward along the strike as closely as 

 possible, considering the limited number of outcrops, they appear 

 to grade into soft argillaceous shales. 



Still further north layers of conglomerate appear interstrati- 

 fied with the sandstones and shales. In addition to well-marked 

 beds of conglomerate, many layers of the sandstone contain 

 pebbles scattered through them. The pebbles are chiefly of 

 quartzite or sandstone, quartz, slate, limestone, feldspar, and 

 rarely of flint. Not a single gneissic or granitic pebble was 

 found, although careful search was made for them. The coarse 

 sandstone and conglomerates, with some shale beds, continue 

 through Bergen county, N. J., and Rockland county, N. Y. 

 Since this phase of the Brunswick group is more resistant than 

 the argillaceous shales in the Raritan basin, the topography is 

 quite different. Where the Brunswick beds are soft red shales, 

 the surface is a gently-rolling lowland, having an average 

 elevation of from 100 to 200 feet above tide. With the appear- 

 ance of the coarser and more resistant beds the general ele- 

 vation becomes greater, and in place of the gently-rolling 

 lowland, we find a series of ridges and valleys following very 

 closely the trend of the beds. Toward the New York state 

 line the higher of these sandstone ridges attain elevations of 

 450 to 625 feet above tide, the local relief being from 200 to 

 300 feet. 



Owing to the disappearance of the Lockatong beds as a 

 group possessing distinctive features, and the change in the 

 Brunswick group due to the appearance of thick beds of brown 

 sandstone and of coarse conglomerate, it is not practicable to 

 differentiate on a map these groups as sharply as could be done 



