TOPOGRAPHY 01" THE NEWARK SYSTEM 197 



As a whole the area has an undulating surface sloping gradually to 

 the southeast, but this is interrupted by conspicuous ridges, including 

 the Watchung or Orange mountains and the Palisades ridge along the 

 Hudson. Southwest of the Watchungs notable elevations occur in Cush- 

 etunk and Eound mountains, Eocky hill, and the broad, plateau-like 

 Sourland mountain. The greatest elevations are 839 feet on Cushetunk 

 mountain south of Lebanon and 900 feet on Barren ridge, a somewhat 

 disconnected part of the Hunterdon plateau south of Pattenburg. 



Barring the conspicuous elevations enumerated above, the plain lies 

 chiefly below 300 feet along the northwestern border, while much of the 

 southeastern border is little above 100 feet. 



Less pronounced but very important irregularities are produced in the 

 surface by the prominent river valleys that have been worn down below 

 the general level. Most notable of these is the Karitan, which has re- 

 duced large areas above New Brunswick to an elevation of less than 50 

 feet above tide. The same is also true of the Hackensack valley Just west 

 of the Palisades ; but this valley is traversed by longitudinal ridges of hard 

 sandstone, while its southwestern part has been depressed below the level 

 of Newark bay and the adjoining meadows. The Delaware river, on the 

 other hand, crosses the Newark area in a narrow trench bordered by 

 bluffs that rise in places from 200 to nearly 500 feet high. In these 

 parts of the valley precipitous cliffs often rise conspicuously on either 

 side of the gorge, and the valley nowhere attains any considerable width. 



CHARACTERS OF THE SEDIMENTARY ROCKS 



The most characteristic sedimentary rocks in the New Jersey Newark 

 are fine grained red shales ; but there are also some sandstones and con- 

 glomerates and, at some horizons, thick massive argillites. Coarse 

 conglomerates occur not only near the base of the series, but also near 

 the top and at various intermediate horizons. Heavy bedded sandstones 

 also occur at various levels, but more abundantly in the lower part. 

 With the black argillites are some layers of gray and green flagstones 

 and occasional thin layers of very calcareous shale, and in the red shales 

 local variations to purple, green, yellow, and black occur.* 



STRUCTURES OF THE NEWARK 



Dip and strike. — The prevailing northeast-southwest trend of the 

 ridges, whether of sedimentary or igneous rocks, is due to the tilting of 

 the strata toward the northwest in a gentle monocline. This general 

 statement is subject to various local exceptions and irregularities, how- 



* The origin of the Newarli sediments is discussed by the writer in the Annual Report 

 of the State Geologist of New Jersey for 1906. 



