Pensauken Formation — Local Details. 95 



concealing its lower edge. The bottom of the pre- Pensauken 

 valley here was as low as the present 40-foot level. 



Between Woodstown and Auburn, there are a few patches of 

 non-arkose gravel on divides and crests, doubtfully correlated 

 with the Pensauken. The patches in question occur at altitudes 

 ranging from 70 to 114 feet, and some of the gravels may be 

 deposits left during the time of general degradation which fol- 

 lowed the deposition of the Bridgeton formation, and preceded 

 the deposition of the Pensauken. 



Below Auburn, the Pensauken is somewhat arkose, a char- 

 acteristic which persists to the northward and northeastward. 

 Even the Bridgeton formation of higher levels did not furnish 

 arkose material, shale, etc., to the Pensauken of the upper part 

 of the valley of Old Mans Creek. If these materials were 

 acquired by this stream in the Pensauken epoch, as seems prob- 

 able, the soft shale and decayed crystalline rock were worn out 

 during their transportation, and do not appear in the gravelly 

 parts of the deposit. The arkose element at Auburn is the con- 

 tribution of the Delaware. Auburn is about the place where 

 the arkose, Delaware phase of the formation meets the non- 

 arkose phase, lying farther from the main stream.. The general 

 relations of the formation in this latitude are shown in Fig. 43. 



A mile and a half northwest of Auburn, there is at least 15 

 feet of arkose sand, with occasional pebbles of red shale. In this 

 vicinity, too, a few bits of trap rock are found, and even an 

 occasional bowlder. Trap rock has not been seen in the Bridge- 

 ton of this general region, and it is believed to have come down 

 the Delaware during this epoch. Here, too, the Pensauken con- 

 tains granite pebbles not seen in the Bridgeton in this vicinity, 

 though bits of gneiss occur in that formation. To the west, the 

 base of the Pensauken descends to 30 feet, or even lower, beneath 

 the Cape May formation. 



At Auburn the non-arkose phase of the formation runs up to 

 the altitude of 100 feet more or less. It is an open question 

 whether the arkose phase reached the same level, being degraded 

 later. 



