1 8 Quaternary Formations of Southern New Jersey. 



toward the supposed pre-Bridgeton Amboy-Bordentown-Salem 

 valley. This decline points to a tract along the present Dela- 

 ware Valley at least 40-50 feet below the low divide to the 

 southeast, at the time the Bridgeton formation was deposited. 



Similar relations hold northeast of Berlin. The erosion sur- 

 face on which the Bridgeton was deposited, or the plain which 

 appears to be the continuation of it, has now an elevation of 

 about 200 feet at Berlin, and thence to Freehold. Above it rose 

 the unreduced hills of the Clarksburg and Crawfords Corner 

 regions. This old plain appears to have sloped southeastward 

 from the divide, declining to 140 feet at Lakewood, 130 feet 

 at Barnegat, 60 feet at Absecon, and 40 feet at Tuckahoe. North 

 of the Amboy-Bordentown Valley, areas at about 200 feet, as 

 in the vicinity of Pennington, may go with this old level. There 

 are tracts of similar elevation in Pennsylvania, as at Norristown, 

 Conshohocken, King of Prussia, Gordon Heights, and along the 

 line of the Pennsylvania Railroad known as the "Cut Off/' 

 running southwest from Trenton. 



ORIGIN. 



According to the interpretation here favored, the accessible 

 parts of both phases of the Bridgeton formation are primarily of 

 terrestrial origin. A part of what now remains may be marine 

 or estuarine, and part of what has been removed may have 

 been. 



The Glassboro Phase. — The material of the Glassboro phase 

 of the formation is believed to have been brought in largely 

 from the north by rivers, and deposited in the wide valley be- 

 tween Amboy and Salem. The antecedent of Hudson River was 

 one of the chief contributors, if it had the course suggested above. 

 Another principal stream from the north was the ancestor of the 

 Raritan, which, at that time, is believed to have flowed up the 

 present Millstone valley to the Amboy-Trenton valley. In the 

 western part of the State, some of the gravel and sand of the 

 formation were probably brought in by the Delaware, and at 

 Philadelphia, the Schuykill made it contribution. Streams lead- 



