THE PALISADES SILL 207 



The position of the Sour land Mountain trap, brought up by the Hopewell 

 fault in a great repeated series of strata all dipping northwest, strongly 

 suggests that it is also a part of the Palisades-Rocky Hill sill. If de- 

 pressed some 6,000 feet, the approximate throw of the fault, according 

 to Kiimmel's estimate, it would fall into line with the probable subter- 

 ranean continuation of the trap of Rocky hill and Pennington and Bald- 

 pate mountains. In a similar manner mount Gilboa, above Lambert- 

 ville, and the smaller isolated trap mass at Byram, each lying on the 

 upthrow side of a fault that repeats a large portion of the sedimentary 

 series, may reasonably be regarded as fragments of the same sill brought 

 up from near its thinner northwestern border (see cross-section along the 

 Delaware river, plate 1). 



Thus the correlation here advocated regards the intrusive trap masses 

 outcropping in the Palisades, in Rocky hill, in Pennington, Baldpate, 

 and Sourland mountains, in mount Gilboa, and the mass at Byram as 

 parts of one continuous intrusive sill. Their present disconnected condi- 

 tion is due to the Cretaceous overlap in the case of the Palisades and 

 Rocky hill, to lobe-like subterranean branching in Pennington and Bald- 

 pate mountains, and to repetition by faulting in Sourland mountain, 

 mount Gilboa, and the Byram mass. Hence there is but one great in- 

 trusive sheet in the Newark of Rew Jersey in contrast with three consid- 

 erable extrusives. 



Offshoots of the Palisades sill. — Snake hill and Little Snake hill are 

 two little knobs of trap that stand up prominently out of the Hacken- 

 sack meadows at distances of a mile and three-eighths and one mile re- 

 spectively from the western slope of the Palisades in Jersey City. If the 

 Palisades trap continues approximately conformable to the sedimentaries 

 under the meadows as it does along the Hudson river, it probably does 

 not lie more than 1,600 and 1,300 feet respectively below the outcrops 

 of the Snake hills, and it would be difficult to construct a section on this 

 basis without connecting them with the great underlying sill. 



The trap dike and intrusive sheet that form the small hill just north 

 of Granton are about 800 feet from the nearest outcrop of the Palisades 

 trap, but they are probably not more than 200 feet from the underlying 

 portions of it and seem to he undoubtedly connected with it. 



Similar dikes and sheets appear at the Arlington copper mines, 4 miles 

 from the Palisades at Jersey City and 6 miles from the trap of First 

 mountain at Montclair. It seems probable that these are also offshoots 

 of the Palisades sill, which, with an average westerly dip of 12 degrees, 

 would lie some 8,000 feet below; but even if the Palisades trap should 



