Pensauken Formation — Local Details. 157 



regarded as probably Pensauken. It is recognized that other 

 correlations might be made, and that in some of its details the one 

 suggested may be erroneous. Variations in elevation are to be 

 expected in deposits of the same ag!e laid down in adjoining 

 drainage basins, even at equal distances from the sea. 



South of Manasquan River. — From the preceding pages, it is 

 clear that the correlation of any gravels and sands on the Atlantic 

 slope with the Pensauken of the Raritan Bay-Trenton-Salem belt, 

 becomes increasingly difficult as distance from that belt increases. 

 The correlations of the Quaternary deposits in the upper basins 

 of the streams flowing northward and westward to the Raritan 

 and the Delaware, are somewhat uncertain at many points. 

 Those in the basin of Swimming River are made with large 

 reservations, and in the basin of Manasquan River there is still 

 more doubt ; so much, indeed, as to make the attempt at detailed 

 correlation futile. Gravels and sands of Pensauken age doubt- 

 less exist south of the Manasquan River, as north of it, but their 

 differentiation from the Bridgeton and other post-Miocene for- 

 mations becomes less and less satisfactory toward the southeast. 



The general fact, as now understood, seems to be that the 

 surface of the Beacon Hill formation, in post-Beacon Hill time, 

 declined steadily to the southeast, at ^an angle which corresponded 

 roughly with the dip of the older Coastal Plain beds. During 

 the period of .erosion which followed, the valleys cut in the surface 

 of the Beacon Hill formation were not very deep, and probably 

 not very wide, as the porous nature of the Beacon Hill and 

 Cohansey formations did not favor great surface run-off. South- 

 east of a line drawn from Bridgeton to Red Bank, it is doubtful 

 if the Beacon Hill and Cohansey formations were ever cut 

 through more than locally, by the streams. 



Later, in the period of Bridgeton deposition, the valleys in 

 the Beacon Hill and Cohansey formations were probably ag- 

 graded, but with material derived from these formations, and at 

 the northwest, from older formations as well. The Bridgeton 

 deposits therefore which are believed to be on the southeastern 

 slope are not very distinct, lithologically or topographically, from 

 the older beds on which they rest. The principal difference in 



