1 6 Quaternary Formations of Southern New Jersey. 



and its differentiation from other formations is difficult, and, in 

 some places, has not been accomplished. 



THE BASE OE THE FORMATION. 



Pre-Bridgeton topography. — Both phases of the Bridgeton 

 formation seem to have been deposited on a surface which had 

 some relief, apparently a relief developed by stream erosion. At 

 any rate, the base of the formation is somewhat irregular, and 

 at some points the irregularities are conspicuous within short 

 distances, as if old valley's had been filled by the deposits (Fig. 

 10). Minor irregularities of other sorts are not rare. 



The present valleys do not follow in detail the courses of the 

 valleys which existed before the Bridgeton epoch. Yet the pre- 

 Bridgeton surface developed by stream erosion is thought to 

 have had some similarity to the present surface. Knapp thinks 

 that a master stream had the general course of the Delaware 

 below Trenton, following roughly the line of contact of the 

 older rocks with the Coastal Plain (Cretaceous and later) for- 

 mations, and that tributaries from the east flowed to this master 

 stream somewhat as now. He believes that these tributary 

 streams headed in a divide which extended roughly from Berlin 

 southwestward to Daretown, a little farther northwest than the 

 present divide between the Delaware and the ocean. Southeast 

 of this divide, the course of the streams is thought to have been 

 southeastward, somewhat as now. 



The divide referred to above is thought to have been continued 

 northeastward, with increasing height, through the Clarksburg- 

 Perrineville region, to Crawfords Corner, a few miles south of 

 Matawan and Keyport, and thence to the Navesink Highlands. 

 It was continued thence, perhaps without interruption, across 

 Staten Island to Long Island. 



If this divide was uninterrupted throughout this distance, the 

 drainage of the Bridgeton epoch was notably different from that 

 of the present time. It may be noted, however, that the above 

 view held by Knapp, is hardly susceptible of demonstration, and 

 that something may be said for the view that the lower Delaware 

 had a more easterly course than now. This view is favored by 



