52 Quaternary Formations of Southern New Jersey. 



posures show, and the abundance of the soft chert' at Apple Pie 

 Hill, together with its topographic position, seem to place the 

 gravel of that place with the Beacon Hill formation, though the 

 correlation is less decisive than could be desired. 



In the Beacon Hill formation the cherts are weathered char- 

 acteristically. The chert pebbles seem to be made up of an irregu- 

 lar network of harder and more insoluble material, filled in with 

 less durable material. On weathering, the less resistant parts 

 become whitish powder, while the skeleton remains hard. At 

 the surface, the decayed part is carried away and the skeleton 

 remains. In secondary gravels derived from the Beacon Hill, 

 the old networks are more or less broken and worn. Occasional 

 fossils in the chert point to its origin from Devonian formations. 



The quartz in the gravel is vein quartz largely. On weathering, 

 the pebbles develop a columnar structure. This may go so far 

 that the little columns separate from one another. Some of the 

 pebbles may be crushed in the hand, even when their outer 

 forms are still perfect. In gravels derived from the Beacon Hill 

 gravel, there are splinters from these pebbles of columnar struc- 

 ture, but decayed pieces of quartz are much less common than 

 in the original Beacon Hill formation. 



In the vicinit}^ of Tuckerton, the section shows gravel and 

 sand interpreted, though not without reservation, as Pensauken. 

 No facts concerning these sands and gravels are known which 

 would preclude their deposition by streams or by the ocean. 

 Since they were deposited, the ocean has doubtless encroached on 

 the shore, carrying away the shoreward part of the formation 

 as originally laid down within the limits of the State. 



Correlation.— From the foregoing it is apparent that the basis 

 for correlating any gravel and sand along the line of this section 

 with the Bridgeton formation, is rather insecure. Such correla- 

 tion must be based on topography more than on anything else. 

 It is to be noted that the possible Bridgeton beds at 160 feet at 

 Bear Swamp Hill, and at 126 feet at Munion Field, are con- 

 siderably nearer the ocean than the areas of Bridgeton at cor- 

 responding levels in other sections. So far forth, this would 

 suggest the greater (pre-Bridgeton) age of these gravels. 



