276 BULLETIN OF THE 



N. Martin's Dock, N. J. (fig. 51). — Two beds of trap appear in the 

 sluiles a little above Martin's Dock on the north (left) bank of the 

 Raritun River about two ruiles below New Brunswick ; they are there- 

 fore about three miles posterior to Palisades — Rocky Hill trap range, 

 which if continuous is here buried under the cretaceous formation. The 

 lower bed is about fifteen feet, the upper two feet thick, and they are 

 separated by some ten inches of slate ; the two are closely parallel to 

 each other and to the strata of shale and sandstone below and above, 

 and all dip ten to twelve degrees westerly ; there is no appearance 

 whatever of the traps cutting across the shaly layers that enclose them. 

 The section may be described as follows, beginning at the bottom. 



Soft, fragile shales, generally red in color, appear along the shore for 

 several hundred feet down stream : occasionally they vary to a fine, 

 sandy layer, six to twelve inches thick, with rather irregular layers, as 

 if disturbed, although the shale below and above is very evenly bedded. 

 Approaching the trap, three to five feet below it, the shale is grayish, 

 but still soft and fissile ; for six or eight inches below the trap, the shale 

 becomes slaty, dark, tending to bluish black, and hard ; but in places 

 two or three inches under the junction occur loose, soft, weathered 

 patches quite unlike the firm, dark shale enclosing them. The trap 

 and shale are not welded together ; all the junctions are separated by 

 open joints, so that no specimen showing the two rocks together could 

 be obtained. The lower heavy trap layer is firm, dense, dark through- 

 out with finer texture at both junctions, and no appearance of vesicular 

 structure ; it breaks into rough columnar blocks, and where these are 

 weathered on the shore, they often have the ragged look of a breccia, 

 but no such structure could be found in the rock in place. The inter- 

 mediate stratum is a hard black ringing slate : in places it shows a 

 slight breaking and disarrangement of its layers, not by cross-faulting or 

 any general disturbance, but more as if kneaded together. The upper 

 trap layer is dark and dense, like the lower. Above it the rock is very 

 rusty from weathering, and shows an open, loose texture for some six 

 inches; the rusty color continues for several feet, and about ten feet 

 from the trap there are normal soft red shales again. 



These trap-sheets must be intrusive, although they show less baking 

 than similar sheets on the Delaware. Cook says (J), 202), speaking of 

 the bedded appearance of the trap here and elsewhere, " So strongly 

 marked are these divisional planes, and so closely do they resemble 

 marks of stratification and even lamination, that good observers are 

 frequently unable to tell which is trap and which is only discolored 



