Pensauken Formation — Description. 85 



these formations could have been carried across the sound to 

 the opposite side, if waves and currents only were the-agents of 

 transportation. 



The line A-B of Fig. 42, referred to repeatedly in the pre- 

 ceding paragraphs, is not to be understood to be an absolute 

 line which materials from opposite directions did not cross. It 

 is rather the line along which materials of northwesterly origin, 

 abundant at the northwestern margin of the belt, become so 

 unimportant quantitatively as to be negligible. If a line were 

 to be drawn representing the northwestern limit of southeastern 

 material plentiful enough to be recognized readily, it would be 

 essentially parallel to A-B, but a little northwest of it. 



Differences in sand go with differences in the coarser materials. 

 Thus where the glauconite is wanting, the sand is, as a rule, 

 more or less arkose. Along the southeastern part of the belt 

 (southeast of A-B, Fig. 42), where glauconite is common, the 

 sand is rarely arkose. Northeast of Crosswicks Creek, there is 

 a rise of 20—40 feet in the base of the Pensauken, going south- 

 east, about where its arkose character disappears. 



Local variations in constitution. — There are some areas where 

 bowlders are much more abundant than in others, irrespective 

 of distance from the northwest border of the formation. Thus 

 in the area southeast of Trenton (near Bordentown), bowlders 

 are relatively abundant, and of larger size than in most other 

 places. This area, it will be noted, is below the point where 

 the Delaware leaves the harder formations north of the Coastal 

 Plain, and takes its course across the Cretaceous system. The 

 bowlders here were probably brought down by the Delaware, 

 and left where its gradient became low on the weaker forma- 

 tions. Another area of abundant bowlders is south of New 

 Brunswick, an area which stands in a somewhat similar relation 

 to the Hudson. 



At Kingston, just south of the Rocky Hill gorge, is the 

 coarsest bed of gravel known in the Pensauken. The material 

 is entirely of northern origin, and was apparently left by a 

 stream which, at the time of deposition, flowed south to this 

 point from the Highlands. The gravel at Kingston is but a 



