14 Quaternary Formations of Southern New Jersey. 



common in a layer of coarse material a few inches thick at its 

 very bottom (Fig. 9). The crystalline rock fragments, the shale, 

 and other distinctly recognized northern materials decrease in 

 abundance southward. 



Much of the sand of this phase of the formation is arkose, 

 and the feldspathic material is, as a rule, completely decayed. 

 The only notable exception is the cores of the larger cobbles and 

 bowlders. The clayey element in the sand is not confined to bits 

 of decayed feldspar; films of clay coat the sand grains in many 

 places, increasing the arkose appearance of the whole. 



The quartz of the gravel is mostly vein quartz, and might 

 have come from the Paleozoic and older formations north of 

 the Coastal Plain. Some of the bits of chert contain fossils 

 which have been identified as Devonian. Much of the quartz 

 and chert of the formation appear to have come directly from 

 the Beacon Hill gravel which onece overlay the older formations 

 of the Coastal Plain, but which was largely removed from the 

 northern part of that plain before the Bridgeton epoch. Some 

 of the sandstone and quartzite also came from the Beacon Hill 

 gravel. 



Another constituent of the gravel is ironstone; that is, bits 

 of sandstone or conglomerate, with iron-oxide cement. These 

 came from the Coastal Plain formations. Most of them are 

 from the Beacon. Hill gravel and the underlying Cohansey sand. 

 Pellets of clay are also found in some places, and these, too, are 

 from the older formations of the Coastal Plain. Locally, the 

 gravel and sand of the Bridgeton beds are cemented by iron 

 oxide. 



Structure. — The sand and gravel are, as a rule, cross-bedded 

 (Fig. 7), but in some cases the exposed face in a pit has an 

 almost massive appearance (Fig. 8). In others there is distinct 

 stratification, emphasized to the eye by long lines of pebbles as 

 seen in the vertical face. In other cases, pebbles are scattered 

 through the sand, while in still others, gravel and sand beds 

 alternate. 



Thickness. — The remnants of the formation, as now found, 

 vary in thickness from those too thin to be identified definitely, 



