Pensauken Formation — Local Details. « 129 



of the deepest sections of the Pensauken known. The well was 

 an open one, and the section was seen from top to bottom. It 

 showed conclusively that the foreign (northern) materials of 

 the Pensauken came in first, and that they were followed by 

 the local, southeastern phase, a conclusion confirmed by hun- 

 dreds of roadside and hillside sections. 



The base of the Pensauken rises from 90 feet at Jamesburg 

 to 120 feet just south of Lower Jamesburg, and to 140 feet at 

 Gravel Hill, 4 miles to the southwest. If, therefore, the Pen- 

 sauken were removed, we should find the Cretaceous surface 

 rising promptly from 90 feet at Jamesburg, to 120 feet just south 

 of Lower Jamesburg, and 20 feet more, four miles farther south. 

 Available data seem to point to the continuation of the 90-foot 

 plain beneath the Pensauken northwest to Princeton and Mon- 

 mouth Junction, although the Cretaceous surface rises to 

 ioo± feet at some points, as 2*4 miles southwest of Dayton, 

 along the electric railway. 



Southwest of Jamesburg in the vicinity of Prospect Plains and 

 Cranbury, exposures show r the same sort of material as about 

 Jamesburg-. Toward Cranbury, bowlders are rather common 

 on the surface. Three to four miles west of Jamesburg the 

 undulating, undrained surface already noted elsewhere reap- 

 pears. The same topography recurs, 1 to 2 miles east of Dayton, 

 and it is still more pronounced west of Rhode Hall, and be- 

 tween Rhode Hall and Fresh Ponds. The relief of the surface 

 here is as much as 20 feet in some places, and is so uneven as 

 to recall morainic topography. Near Fresh Ponds, as the name 

 implies, small ponds are common in the depressions, which are 

 3 to 8 feet deep and the ponds 2 to 10 rods across. The de- 

 pressions at Fresh Ponds are, however, not so deep as toward 

 Rhode Hall ; but the Cretaceous clay is apparently nearer the 

 surface about Fresh Ponds,' and so the depressions hold water 

 better. Many of the original marshes and ponds have been 

 drained, and cuts through the rims of the basins have been seen 

 during the process. They are composed of loose gravel and 

 sand, and the same materials lie below the basins themselves 

 where cuts have been seen. The water in the basins is doubt- 



9 QUAT 



