376 HENRY B. KUMMEL 
although the latter did not cease. Consequently there are, in addition 
to the deposits referred to these formations, others accumulated dur- 
ing intervals of erosion, whose lithologic, topographic, and age relations 
are not so clear. Changes of elevation are believed to have accom- 
panied and to some extent to have caused the alternate periods of 
erosion and deposition, but it is not believed that subsidence was so 
great as to have depressed all the region in which these beds are now 
found below sea-level. 
Bridgeton jormation—The Bridgeton formation is essentially 
gravel and sand, the material having been derived from the Beacon 
Hill, Cohansey, Miocene, Cretaceous, Triassic, Paleozoic, and 
crystalline formations. Material from the crystallines and Triassic 
is almost uniformly friable and crumbles readily. Some bowlders 
are so large and of such a character as to have hardly reached their 
present position without the aid of floating ice. It occurs as outliers 
capping high hills, and on divides, and is manifestly now only a 
remnant of an ancient deposit in large part fluviatile and referable in 
time of origin to a very early glacial epoch. 
The Bridgeton is comparable in a general way to the Sunderland 
of Maryland, although their limits may not be the same and some- 
what diverse views of origin are held by workers in the respective 
fields. After the deposition of the Bridgeton, there was a long period 
of erosion during which much of the Bridgeton was removed, par- 
ticularly in Delaware Valley and along the broad belt of low land 
stretching across the state from Bordentown and Trenton to Raritan 
Bay. 
Pensauken jormation—The Pensauken formation is chiefly 
gravel and sand, although locally it contains beds of clay. It fre- 
quently much resembles the Bridgeton and cannot always be dis- 
tinguished from it on lithologic grounds. Where both are present, 
however, it uniformly occurs at lower levels and has suffered less 
erosion. It obliterated the smaller and partially filled the larger 
valleys eroded in post-Bridgeton time, forming broad flood-plain 
deposits along the drainage lines. The coastal portion of the state 
was more or less submerged during this period of deposition but the 
Pensauken formation is conceived to be one due primarily to fluviatile 
rather than marine or littoral conditions. Since glaciated material 
