206 J. V. LEWIS NEWARK TRAP ROCKS OF NEW JERSEY 



Feet 



Clay, saud, aud gravel 75 



Red shale 3 



Trap rock 70 



Red sandstone 2 



Trap rock 7 



Total 157 



Evidentl)' a sandstone inclusion in the trap was here encountered. Two 

 wells bored at Maurer, 2 miles north of Perth Amboy, found trap under 

 64 and 78 feet respectively of sand and clay. In a well a mile and a 

 quarter south of Woodbridge hard rock was found at a depth of 63 

 feet. At first this was supposed to be trap, but afterward it proved to be 

 indurated shale and sandstone, and is doubtless the metamorphic sedi- 

 ment overlying the trap. 



At Keasby, on the Earitan river 2 miles west of Perth Amboy, hard 

 rock, probably trap, was encoxintered under 72 feet of sand and clay. In 

 dredging and blasting operations in the Earitan river a mile below Mar- 

 tin's dock a reef of indurated shale 500 feet wide was found crossing the 

 river in a northeast-southwest course, 5 to 12 feet below low water. No 

 trap rock was found, but it cannot be doubted that this corresponds to the 

 belt of "baked" shales everywhere skirting the intrusive sills. 



Again, 2 miles southeast of Deans, near Fresh Ponds, a bored well en- 

 countered trap rock under 60 feet of clay, unquestionably the buried 

 margin of the Eocky Hill mass which outcrops abundantly about Deans.* 



The several dikes east, south, and west of New Brunswick bear the 

 same relation to this covered extension of the sill as do those of Arling- 

 ton, Snake hills, Granton, and Bogota to its prominent outcrop in the 

 Palisades. The Eocky Hill tr-ap lies at a much higher horizon than the 

 Palisades, but it descends rapidly eastward, and a continuation of this 

 under the Cretaceous cover would readily unite it with the Palisades sill. 

 Furthermore, the Eocky Hill sill increases in thickness eastward from 

 its narrow outcrop near Hopewell, and a similar thickening is continued 

 in the Palisades sill northward from Staten island and Bergen point. 



The intrusive traps of Pennington and Baldpate mountains (P and B, 

 plate 1) are doubtless continuous with the Eocky Hill sill, as also sug- 

 gested by Darton, and are to be considered as lobe-like protrusions which 

 probably merge into the same mass at no great depth. The irregular 

 forms of these mountains and the northeastward apophysis of Eocky hill 

 indicate subterranean branching of the lavas in this region. 



* In the order given, the above data are recorded in the Annual Reports of the State 

 Geologist of New Jersey for the following years : 1896, p. 199; 1904, pp. 265, 268; 

 1895, p. 93 ; 1898, pp. 131, 132 ; 1882, p. 59 ; 1895, p. 93 ; 1900, p. 159. The well near 

 Woodbridge, however, was erroneously reported as southwest of the town. 



