ii2 Quaternary Formations of Southern New Jersey. 



On the whole, the material of the area is chiefly coarse arkose 

 sand, with coarse gravel, cobbles and even bowlders at the base. 



In the vicinity of Cross wicks there is a considerable area of 

 aikose Pensauken south of the creek. The character of the 

 material is like that at Bordentown. Its base is at such eleva- 

 tions as to indicate that a valley occupied approximately the site 

 of the present Crosswicks Creek in pre-Pensauken time. 



In general the Pensauken is coarser, and contains more north- 

 ern and arkose material near the Delaware, and is finer, with 

 less arkose material, farther back from the river. At the east, 

 there is local material only; at the west, northern material, 

 chiefly; and in a belt between, the two are somewhat mingled 

 and interbedded. The interbedding and intermingling are 

 chiefly along the southeast border of the Swedesboro Plain, 

 near the base of the old scarp which marked its southeastern 

 limit. The Swedesboro Plain here has an altitude of 50 to 80 

 feet, and is 20 to 40 feet below the scarp to the southeast. The 

 structure of the arkose phase is not unlike the structure of the 

 valley train of the last glacial epoch, above Trenton. The Dela- 

 ware phase of the formation spread 2 to 4 miles from the 

 present stream. A similar condition of things existed on the 

 west side of the Delaware. 



Between Rancocas and Crosszvicks creeks; non-arkose phase. 

 — East of the arkose phase of the Pensauken between these 

 creeks, there are many patches of gravel and glauconitic sand, 

 representing the non-arkose phase of the formation. They occur 

 at elevations similar to those of the arkose phase, and slightly 

 higher. Some of the larger areas are at Columbus, on the divides 

 between Jobstown, Juliustown, and Arneys Mount, and on those 

 about Georgetown. The gravel is thin, 4 feet being an unusual 

 thickness, and the material is mostly quartz and ironstone. 

 Glauconitic sand and loam are more abundant than gravel. The 

 altitude of the bases of these patches ranges from 50 feet up to> 

 130 feet. Their correlation with one another, and all with the 

 Pensauken, is open to question, but manv of them are at the level 

 of 80 to 90 feet, which makes their reference to the Pensauken 

 reasonable. 



