136 Quaternary Formations of Southern New Jersey. 



decayed to the very center; while others have a 2- or 3-inch 

 core which is firm. A large part of the thick deposit is of large 

 cobbles, yet there is matrix enough so that the material stands 

 with vertical faces year after year. The gravel fills a river 

 gorge from an elevation of 50 or 55 feet up tor 100 feet, and 

 then spreads out on the higher land to the east of the gorge. 

 The gravel came from the north, and apparently it must have 

 been brought in by a stream which flowed south. Down to this 

 point the river must have been swift to have brought in the 

 coarse material, which becomes finer and finer with increasing 

 distance from the gorge. The southward connection of the 

 valley of the stream which deposited the Kingston gravel is 

 not known. 



Pensauken gravel and sand cover much of the area between 

 Monmouth Junction and Kingston northwest of the Pennsyl- 

 vania Railroad. The base of the formation here has an eleva- 

 tion of 80 to 100 feet, being highest at the west. 



North of the Raritan. — The Pensauken is well developed in a 

 triangular area roughly outlined by lines drawn between Me- 

 tuchen, Bonhamtown and Piscataway. It covers the contact of 

 the Newark and Raritan, overlapping it in both directions. 

 Mill Brook and the lower end of Piscataway Creek have cut 

 through the Pensauken and have their channels in the Newark 

 shale. When Pensauken deposition took place here, remnants only 

 of the Raritan formation remained, and the Pensauken buried 

 Newark and Raritan alike. The general disposition and rela- 

 tions of the formation between Metuchen and South Amboy are 

 shown in Fig. 54. 



The surface of the Pensauken now slopes from a maximum 

 elevation of 134 feet near Metuchen, to 100 feet or less at Bon- 

 hamtown ; in other words, it has a gentle slope to the southeast. 

 The base of the formation is lowest along a line southwest from 

 Bonhamtown, and higher to the southeast and northwest of this 

 line. The belt where the base is lowest doubtless marks the site 

 of a pre-Pensauken valley. Mill Brook follows this old valley 

 more than a mile southwest of Bonhamtown, and there it turns 

 south and follows a post-Pensauken valley to the Raritan. 



