132 Quaternary Formations of Southern New Jersey. 



Dunhams Corners), but declines northward toward Lawrence 

 Brook. Along* the south bank of Beaver Dam Brook, its base 

 declines from about 100 feet west of Dunhams Corners to 60 

 or 65 feet at Lawrence Brook. In the valley north of Fresh 

 Ponds, its base declines from about ioo< feet south of Dunhams 

 Corners to 80 feet. 



In the area about Dunhams Corners there are many depres- 

 sions without outlets, similar to those at various points to the 

 southwest. Some of the depressions contain marshes and ponds, 

 while others are dry. The ponds and marshes are believed to 

 point to the proximity of Cretaceous clay below, the dry basins to 

 a greater thickness of Pensauken, or to underlying) Cretaceous 

 sands, as distinct from clay ; but these relations can hardly be 

 said to be demonstrated. The surface about Dunhams Corners 

 shows a good deal of coarse stony material. 



East of Lawrence Brook and northeast of Milltown, there are 

 some patches of Pensauken, mostly thin, which represent the 

 basal part of the formation. 



The Pensauken surface reaches an altitude of 163 feet at Old 

 Bridge, and its base is at 90 to 100 feet. The upland covered by 

 the Pensauken drops off suddenly to the valley of South River 

 by a scarp, facing southeast. 



Lawrence Brook and drainage changes. — Lawrence Brook 

 follows approximately the junction of the Newark shale and the 

 Cretaceous system from' Deans to Milltown, a position which sug- 

 gests its adjustment to structure. Its course most of the way is 

 actually a fraction of a mile off the contact, its channel being in 

 Newark shale (locally trap) most of the way. Judging by the 

 disposition of the Pensauken, there was a valley at the contact 

 of the Newark and the Cretaceous beds in pre-Pensauken time, 

 for remnants of the Pensauken formation occur along this line 

 at lower levels than to the northwest and southeast. This holds 

 down the valley to its junction with the Raritan. The pre- 

 Pensauken valley floor declines from an elevation which is now 70 

 feet at Deans, to 60 feet at Westons Mills ; but the valley was 

 narrower at the latter place than at the former. 



