126 Quaternary Formations of Southern New Jersey. 



covered with Pensauken gravel to the depth of 20 to 30 feet. A 

 mile or so south of Hightstown, the Pensauken is some 30 feet 

 thick where the surface has an elevation of about 130 feet. These 

 facts show how abruptly the thick body of the formation ter- 

 minates at the southeast. The pre-Pensauken surface seems to 

 have risen 40 feet at least in half a mile along 1 the east edge of 

 the Pensauken formation. The relations are similar to those at 

 Swedesboro, where the high-level Pensauken drops off from 115 

 feet, to the low-level phase of the formation, at 70 ox 80 feet. 



East of Hightstown, a considerable area of Pensauken covers 

 the divide between Millstone River and Rocky Brook. Arkose 

 sand in its various phases is exposed at several points here. 

 The general disposition of the formation between Swedesboro 

 and Hightstown is shown in Fig. 52 (p. 136). 



Between the Millstone River and Cranbury Brc-ok. — The 

 broad low divide between these streams is covered continuously 

 with Pensauken from Old Church and Red Tavern on the south- 

 east, nearly to the junction of the streams. The elevation of its 

 base is about 120 feet at Red Tavern, but declines rapidly to 90 

 feet to the northwest, and then gradually to 70 feet. The sur- 

 face is characterized by some cobbles and bowlders, among them 

 trap, and in places by the undulatory topography already .noted 

 near Edinburgh. Such an area occurs 3^2 miles west of Cran- 

 bury Station, at the 100-foot level. A trap bowlder 4 to 5 feet 

 in diameter occurs southwest of Cranbury Station, in the valley. 

 This is some 9 miles from the nearest outcrop of trap. These 

 trap bowlders, as well as the others of the region, are doubtless 

 from the Pensauken, and appear most commonly where that 

 formation has been mostly eroded away. 



Outlying areas of Pensauken. — Northwest of the Pennsyl- 

 vania Railroad there are a few outliers of the Pensauken forma- 

 tion. The largest is at Penns Neck, capping the higher part of 

 the tract between Millstone River, Stony Brook, Duck Pond 

 Run, and the railroad. This Penns Neck area appears to have 

 been surrounded by the drainage of the last glacial epoch, mak- 

 ing it an island. 



