224 The Physical History of the Trias 



A few miles southwest of Arlington occur the extensive 

 .Newark quarries, where these sedimentary rocks are again 

 well exposed. Here the sandstones are more heavily bedded, 

 the strata being in some cases fifteen or twenty feet thick, 

 with the usual dip of 10 to 15 degrees toward the northwest. 

 These quarries furnish great quantities of fine building-stone, 

 largely used in the neighboring cities, which is composed of 

 grains of quartz and felspar, cemented with oxide of iron and 

 argillaceous material, and sometimes spangled with mica. 



Again in Elizabeth, along the New Jersey Central railroad, 

 the red shales and sandstones are well shown for a short dis- 

 tance, and exhibit a striking constancy both in the dip and in 

 the uniform thickness of the strata. 



Farther south, at N"ew Brunswick, the red shales are beauti- 

 fully displayed on the south bank of the Raritan river, about 

 a mile westward of the town. They show their parallel 

 planes of deposition, dipping with extreme regularity at an 

 angle of 15 degrees toward the northwest. These layers are 

 often but an inch or two thick, and very uniform in bedding. 

 On the Delaware, the Triassic area attains a width of thirty 

 miles — the longest section in any portion of this belt. 

 Throughout this whole distance the rocks present the well- 

 known alternation of sandstones and shales, with the usual 

 northwestward inclination. There are local exceptions, how- - 

 ever, along this Delaware section, to the entire uniformity of 

 dip which characterizes these beds in ISTew Jersey,— due to the 

 disturbance which some of the injected trap-sheets have 

 effected in the arrangement of the sedimentary beds. 



These few examples have been selected from a great num- 

 ber of exposures examined by the writer, and may be taken 

 as representing the general geological characters of the red 



The bedding of the sandstone and shale seems undisturbed where they ap- 

 proach the cleft. The metamorphic action is not confined to the imme- 

 diate walls of the fracture, but extends at least 75 or 100 feet on either side. 

 These facts seem strongly to indicate that the fissure, not far below, is filled 

 with igneous rock, which reached near enough to the present surface to make 

 its influence felt. 



