Bridgeton Formation' — Local Details. 33 



here gravelly, rests on characteristic fine Miocene sand, and the 

 distinction between the two is therefore clear. In general, the 

 base declines toward Edwards Run on the west, and towards 

 Chestnut Branch on the east. 



The base is much more regular about Cross Keys, Downer 

 (about 150 feet), and Glassboro (about 140 feet) than about 

 Barnsboro and Jefferson. In the vicinity o<f Barnsboro, indeed, 

 it is evident from the base of the formation that there were 

 pre-Bridgeton valleys leading westward toward the Delaware. 

 The irregularities of base here are similar to those about Aldine 

 (p. 27). There are also some irregularities in the base of the 

 Bridgeton in the vicinity of Pitman Grove and Dilkesborough. 



Exposures. — A mile or more northwest of Barnsboro, there 

 are gravel pits, showing the nature of the Bridgeton at this 

 locality. Some of the material is coarse, ranging up to bowlder- 

 size, and the gravel is compact. In some exposures, the gravel 

 is confined mainly to the base, and in some places there is a con- 

 spicuous cobble bed in this position. 



There is another exposure a third of a mile or so southeast 

 of Barnsboro, on the Pitman Grove road, where 15 feet of 

 Bridgeton gravel overlies the Miocene. There is rather less 

 sand, loam, etc., associated with the gravel here than in most 

 places, and the gravel itself is finer than is its wont. At Pitman 

 Grove there are extensive exposures along the railway showing 

 the base of the formation at an altitude of about 120 feet. Its 

 base has the abundance of foreign material characteristic of the 

 gravelly layer at the bottom. Bowlders even 3 feet or more in 

 diameter are to be found, though they are rare. 



BETWEEN MANTUA CREEK AND BIG TIMBER CREEK. 



Distribution. — Between the headwaters of these creeks, and 

 between the upper parts of the south and north branches of 

 Timber Creek, south of Point Pleasant, the Bridgeton formation 

 is found in considerable areas at elevations of 150 to 170 feet; 

 but northwest of Cross Keys it is found only on the divides 

 (Fig. 20). Its most northwesterly remnant is on Irish Hill, 

 3 QUAT 



