Bridgeton Formation— Local Details. 63 



ginning of Bridgeton time, so as to give a steep g'radient to the 

 southwest, such elevation should have affected the streams flow- 

 ing from Freehold to the ocean, unless the coast were cor- 

 respondingly farther out. If the streams flowing- to the south- 

 east were affected by such an elevation, they should have deepened 

 their alleys; but we find no evidence that the valleys were so 

 deepened at this time. If, on the other hand, the region about 

 Berlin subsided while the region at Freehold remained 100 to 150 

 feet above tide, there might have been sufficient grade to carry 

 material from Hightstown to Berlin. 



A possible explanation of the difficulties is found in the posi- 

 tion of the coast line in the Bridgeton period. The eastern 

 coast suggests that it has been encroached upon by the sea in 

 post-Bridgeton time. From Toms River north, it probably lay 

 much farther east in the Bridgeton epoch than now. If the 

 coast line were some 30 miles east of the present coast in the 

 vicinity of Asbury Park and Long Branch, some of the diffi- 

 culties would be met. 



If we assume that the old pre-Bridgeton lowland, in the vicin- 

 ity of Hightstown and Amboy, was below the present 150-foot 

 level, the Bridgeton base was below the top of the Pensauken, 

 and all hope of separating the two formations, on topographic 

 grounds, is gone. 



The difficulty, therefore, appears as follows : The material 

 between Amboy and Trenton regarded as Pensauken has a maxi- 

 mum altitude (surface) of nearly 190 feet at Amboy and a 

 minimum altitude (base) of 60 feet in the vicinity of Amboy 

 and Sayreville. It has a maximum (surface) altitude of 130 

 or 120 feet in the vicinity of Trenton and a minimum (base) 

 of 10 or 20 feet. The material, however, appears to be a unit 

 throughout this entire area, and throughout this vertical range. 

 If the gravels at elevations of 150 feet at Hightstown and those 

 still higher at Amboy are Bridgeton, we have no means of 

 demonstrating that all the gravels down to the 20-foot level at 

 Trenton are not Bridgeton. This assumption would lead us 

 into still greater difficulties south of Trenton. 



