CLAYS OF CRETACEOUS FORMATION. 165 



marked contrast to the Clay Marl and Marl series, which, by 

 their constitution, indicate deeper water, uniform, conditions over 

 much wider areas, marine rather than brackish water, and a tend- 

 ency to uniform, rather than strongly varying rates of accumu- 

 lation. 



Location. — The area occupied by the Raritan series is shown 

 upon the accompanying" map, Plate X. It forms a broad belt, 

 extending from Raritan bay across the State to Trenton and 

 Bordentown, and a much narrower strip along- the Delaware river 

 to Salem county. Its greatest width is something - over 8 miles, 

 while for a few miles below Bordentown it is limited in outcrop 

 to the face of the bluff above the river, and the side slopes of the 

 neighboring ravines, the greater part of the outcrop! belt being 

 beneath the bed of the river. Over most of its outcrop across the 

 State its surface is more or less covered by later deposits of 

 sand and gravel, the Pensauken or later formations. These are 

 often so thick as to conceal effectually the beds beneath, and in 

 not a few localities to hinder or entirely prevent digging or even 

 prospecting for clay. This is particularly the case in the flat, 

 low-lying portion of the State from Fresh Ponds and Spots- 

 wood to Trenton. Within this area it is not only impossible 

 to make out any subdivisions in the Raritan, but it is a matter 

 of some difficulty even to determine accurately its boundaries. 

 Nevertheless, occasional well borings show that extensive beds 

 of clay occur within this area, although not at horizons which 

 render them economically valuable. 



Northeastern Middlesex County. 



Within the region lying between Woodbridge, South River 

 and Cliffwood, shown in detail on the maps, Plates XI and XII. 1 

 it has been possible to subdivide the Raritan formation into nine 

 members, which can be differentiated and mapped with reason- 

 able accuracy. These are as follows, beginning at the top : 



1 These maps are described in detail in Appendix E. 



