Pensauken Formation — Description. 69 



deposits made in them during the Pensauken epoch have not been 

 clearly differentiated in most parts of the southeastern slope. 



Pensauken deposition. — After the development of these broad 

 valley-plains of erosion, conditions became such as to cause 

 deposition upon them, and these deposits constitute the Pensauken 

 formation. The principal part of the formation, and the part 

 which is most distinctive, was deposited on the valley lowland 

 between Raritan Bay and Salem. Contemporaneous deposits 

 elsewhere were less extensive, less distinctive, and difficult of 

 differentiation. 



The conditions and the agents of deposition have been much 

 discussed, and there is still difference of opinion concerning them. 

 The chief opposing views are (1) that the plains of erosion 

 referred to above were submerged, and that the deposition which 

 followed was marine; (2) that the plains were not submerged, 

 and that the deposits were fluvial; and (3) that submergence 

 was partial, and that the deposits are partly marine and partly 

 fluvial. 



According to the interpretation of the formation which 

 assigns to it a fluvial origin, its material was brought to the 

 Raritan Bay-Trenton-Salem plain by drainage from the north. 

 The principal contributing streams were the Hudson, the Raritan 

 and the Delaware, or their predecessors. This view carries with 

 it the hypothesis that Raritan River then flowed southward 

 from the mouth of the present Millstone, up the valley of that 

 stream, to the master stream in the Raritan Bay-Trenton valley. 



On the hypothesis that the Pensauken deposits are terrestrial, 

 they are thought to have been made at a time when the streams 

 from the north bore the gravel, sand, etc., of the melting ice of 

 one of the early glacial epochs. This view is based on the 

 physical and lithological characteristics of the deposits. If this 

 interpretation of the origin of the formation is correct, that part 

 of it in the Raritan Bay-Bordentown-Salem valley is a sort of 

 broad valley train. One of the difficulties of this interpretation 

 is that the materials do not decrease regularly in coarseness down 

 the valley as in a normal valley train. 



