IRON CONCRETIONS OF REDBANK SANDS 245 



E. N. E., the dip being slight. In some exposures they are seen to 

 occur in parallel zones which are considerably inclined to the normal 

 dip of the strata in this region. As noted above, their distribution 

 through the sand is, in general, irregular. In some large areas they 

 appear to be totally absent, and occur but sparsely in others. In still 

 other areas they are found in crowded aggregations containing an 

 enormous number of individuals, all having the characteristic orienta- 

 tion. Where the concretions lie thickly crowded together, this common 

 orientation gives them an appearance suggestive of great piles of 

 cord-wood partially covered with sand. Such aggregations, which 



Fig. 2 



are often elongate in the same direction as the concretions themselves, 

 are locally so numerous and large as to impress a peculiar stamp upon 

 the topography, as they serve to protect the loose sand beneath from 

 erosion ; the resulting uniformly oriented hills of circumdenudation 

 have somewhat the shape of drumlins. Such hills are numerous on 

 the outcrop of the formation in the eastern part of Monmouth County.' 

 The most interesting specimens are not usually found in these situa- 

 tions, as the abundance of iron has led to a thickening of walls and a 

 running together of outlines. The best ones are to be obtained where 

 the glauconite was sparingly disseminated, as in the large cut on the 

 New York & Long Branch Railroad one mile west of Redbank. In 

 this and many other localities the concretions may be dug out of the 

 sand with no other implement than the bare hand ; the interior filhng 

 may be removed by shaking, or with the aid of a straight stick. 



iSee Sandy Hook Sheet, U. S. Geological Survey (topographic map) south of 

 Eatontown and thence east to Long Branch. 



