138 A 7 ". H. Darton — Trap of New Jersey. 



for in one instance over 150 feet, and trap offshoots are sent 

 down or out into the underlying beds. In the vicinity of 

 Haverstraw the crescentic course of the dike causes a corres- 

 ponding deflection in the line of outcrop, and although this is 

 greatly aided by the structure of the outlying beds, the base 

 of the sheet crosses the strata for several hundred feet in 

 preserving its position above the surface. At its terminal out- 

 crop, an occurrence of vesicular rock, suggests that the sheet 

 was finally extruded. At its contacts with enclosing strata the 

 Palisade trap becomes fine-grained, very dense and bedded in 

 structure, and the sedimentary rocks are darkened and hard- 

 ened often to a considerable distance. 



A short distance west of the Palisade trap near the latitude 

 of the city of New York, are the posterior trap masses of 

 Granton and Snake Hills, similar structurally to the Palisade 

 trap in consisting of a dike and a sheet extending up the dip. 



While it seems probable that the Palisade trap continues 

 southward to reappear in the series of outcrops which extend 

 from Lawrence Brook through Rocky Hill and Pennington 

 Mountain to Bald Pate and Jericho Hill on the Delaware, it 

 is possible that it is due to an entirely separate intrusion. 

 The trap of the series of outcrop from Lawrence Brook to 

 Jericho Hill is similar to the Palisade sheet structurally and 

 petrographically, and is apparently a continuous mass not reach- 

 ing the surface in the gaps that isolate Pennington Mountain. 

 It is heavily flanked with indurated shales and crosses the strike 

 of the enclosing strata, both at intervals in its westerly course 

 and in the hooked outcrop of Ten Mile Run Mountain. 



Sourland Mountain consists of a thick sheet of coarse- 

 grained diabase, heavily flanked by highly indurated shales, 

 and follows the strike of the enclosing strata excepting in a 

 local bowing near the center of its course where it crosses and 

 recrosses the strata for a short distance. Cushetunk and Round 

 Mountains are the remnants of a wide, thick, intrusive sheet 

 considerabty flexed, and eroded through at the anticlinals so as 

 to give the singular horse-shoe shaped course to Cushetunk 

 Mountain and isolation to Round Mountain. The indurated 

 strata associated with this trap are crossed by it at some points, 

 and along the western border for a short distance the edge of 

 the sheet overlaps the Lower Paleozoic limestones and presents 

 some evidence of having been extrusive. 



The smaller trap masses along the Delaware, at Belle Moun- 

 tain, Brookville, and Point Pleasant, are all local intrusive 

 sheets intercalated between highly altered strata, and near 

 Neshanic, Martin's Dock, and Arlington are other intrusive 

 sheets, finely exposed in cross-section. The other trap masses 

 in the New Jersey region are some small sheets and dikes near 



