Pensauken Formation — Local Details. ioi 



of arkose sand. The stony matter of the upper member is 

 coarse, up to I foot in diameter, and pebbles are not wanting 

 in the lower, which is glauconitic. At other places in the 

 vicinity much of the material is cemented by iron, or its 

 grains and pebbles are coated with it. Near Mantua Creek, the 

 arkose Pensauken occurs up to 76 feet near Tatems. This, 

 with its position to the southwest, suggests the building up of 

 the Swedesboro Plain by the Pensauken deposits to 70 or 80 

 feet. 



To the east of these principal areas of arkose Pensauken, 

 there are numerous areas of the non-arkose phase of the forma- 

 tion, the areas being poorly defined, and their correlation more 

 or less uncertain. In general, this phase of the formation is 

 higher than the arkose phase, and it is found neither in the 

 valleys nor on the highest lands, but over areas of intermediate 

 height. Not rarely it caps low divides and broad flatfish areas 

 above valley bottoms and valley terraces. In some places it 

 occurs in elongate belts more or less parallel to the stream, as 

 above Wenonah, above Blackwood, and above Chews Landing. 

 The elongate patches in these positions suggest that the ma- 

 terials concerned are stream deposits, subsequently left as low 

 ridges by the migration of the streams. 



Proof that the arkose Pensauken to the west and the local 

 Pensauken to the east were absolutely contemporaneous, is 

 wanting. The two do not grade into each other, but their posi- 

 tions suggest their contemporaneity, especially if both are pri- 

 marily the work of streams. Up the valley of Mantua Creek, 

 just south of Wenonah, a considerable bed of gravel caps the 

 low divide between Chestnut Creek and the main valley. The 

 base of this gravel has an elevation of 50 to 70 feet. The top 

 rises to 80 feet, and still higher toward Sewell. In position, 

 these gravels are in harmony with those near Mickelton and 

 Woodbury. 



It appears that when Pensauken deposition began, the Swedes- 

 boro lowland was uneven, and that it was built up by the Pen- 

 sauken arkose deposits to what is now the 80-foot level in the 

 vicinity of Woodstown,.and to 120 feet in the vicinity of Haddon- 



