6o Quaternary Formations of Southern New Jersey. 



able that these several formations here overlap one another ; that 

 is, that they are more or less imbricated. 



Bridget on base northwest of Clarksburg. — To the northwest of 

 the Clarksburg hills, there is difficulty in identifying the Bridge- 

 ton formation and in determining the level at which it should 

 occur. Between Disbrows Hill and Rocky Hill (Fig. 34) is the 

 broad lowland covered by the Pensauken formation. Northwest 

 of the Pensauken area there is a tract near Princeton, more than 

 200 feet in elevation. This elevation stands in about the same 

 relation to Rocky Hill that Disbrows Hill does to the Clarks- 

 burg hills. 



At at elevation of about 220 feet in the vicinity of Lawrence- 

 ville southwest of Princeton, patches of gravel are found. Yhey 

 are too low to be correlated with the Beacon Hill gravel, and too 

 high for Pensauken, and for these reasons are regarded as prob- 

 ably Bridgeton remnants. 



Near Pennington, 7 miles west of Princeton, there are bowl- 

 ders, gravel, etc., at elevations of 200 to 240 feet, and this level 

 seems to represent a rather definite former plain of degradation. 

 The bowlders are regarded as probable remnants of the Bridge- 

 ton cover which once overlay the region. 



Near Disbrows Hill, the section shows lesser hills at 160 to 

 180 feet. These hills are in reality a little south of Disbrows 

 Hill, but the section shows their proper relations stratigraphic- 

 ally and topographically. Their gravel caps may be Bridgeton 

 or post-Bridgeton, and their correlation is open to question. 



The pre-Bridgeton surface southeast of the Clarksburg hills 

 appears to have had an altitude of about 200 feet and to have 

 declined to the southeast. This plain of degradation was prob- 

 ably developed by streams 25 to 40 miles in length. Northwest 

 of the Clarksburg hills the pre-Bridgeton plain was probably 

 developed by the great river which flowed through the Amboy- 

 Bordentown valley, and by its tributaries. If this is so, the plain 

 developed by this master stream should have been lower than the 

 plains to the southeast developed by many small streams. The 

 Delaware now has its bed down to ti^e level up to Trenton, 100 

 miles or so from the ocean proper. The larger stream of earlier 



