43 



Geology of Hudson County, New Jersey. 



The open fissure at Arlington, which is without doubt filled 

 below with trap, and other thin sheets of the same rock pene- 

 trating the sandstone in the Schuyler mine, also nid us in un- 

 derstanding the genesis of the Triassic trap-rocks. 



Grouping all these phenomena together, we are enabled to 

 construct an ideal trap-sheet, as it would appear while yet in- 

 closed in the stratified rocks among which it was intruded, or 

 before it was exposed by denudation. A cross-section of such an 

 ideal trap-sheet is shown in the following diagram, Avhich repre- 

 sents a main intrusion of trap like that forming the Palisades 

 or the First Newark Mountain, with its branching or secondary 

 sheets and dikes. 



Fig. 3. — Ideal Section of Trap-Sheet. 



c w 



% 



]S.W. 



S. E. 



If denudation should have removed the material to the 

 right of the line C, D, — an exposure would be made similar to 

 that now seen in the cliffs at Weehawken. Were the rocks 

 above the dotted line E, F, G, removed, the trap-sheet at 

 i^ would protrude and form a hill, like Snake Hill and Little 

 Snake Hill, while the sheet E, when denuded and rounded 

 off, Avould correspond with the Ioav ridge of trap along the west- 

 ern border of Bergen Hill. In the same manner, if the acci- 

 dents of erosion should expose the rocks along the line A, B, 

 the conditions now shown at Plainfield and Bound Brook would 

 result. The Arlino-ton fissure is indicated at G. 



