184 CLAYS AND CLAY INDUSTRY. 



inated clay at the top is overlain by a white, micaceous sand, that 

 is by the next higher Cretaceous bed, there has been no erosion of 

 the Woodbridge clay (Plate XX, Fig. 2). This is the case in 

 most of the banks about Maurer and Keasbey, and at Sayreville. 

 Here, however, the base of the clay lies so deep that it is below 

 sea level and is reached only by borings. The thicknesses given 

 above make due allowance for the upper layers where they have 

 been eroded, or are based on the data furnished by borings where 

 the base of the clay is not exposed. 



The Woodbridge clays do> not form, a homogeneous bed, but are 

 made up of many layers of varying quality. At the top there is a 

 black, lignitic clay with alternating seams and layers of sand. 

 These were called by Dr. Cook the "laminated clays and sands." 

 At the base there is a bed of fire clay, — Cook's Woodbridge fire- 

 clay bed. In some areas certain beds just above the fire clay have 

 a marked individuality, and can be recognized in adjoining banks. 

 Elsewhere the corresponding layers are not sharply separable from 

 the laminated clays and are included with them. 



The black laminated clays. — As above noted, the upper portion 

 of the Woodbridge -clay bed consists of a succession of beds of 

 black clay carrying some lignite and pyrite, and alternating with 

 thin seams of white quartz sand, which is often darkened by dis- 

 seminated bits of lignite. There is no order or regularity in this 

 alternation. Both the clay and the san4 layers vary in every con- 

 ceivable manner in thickness and position. Locally the clay beds 

 are thick and the sand is reduced to leaf-like partings ; elsewhere 

 the reverse may be true, and the greater part of the section may 

 be sand, although the clay predominates on the whole. Layers of 

 clay from one-eighth to one-fourth of an inch in thickness, sepa- 

 rated by seams of sand scarcely thicker than a sheet of stiff paper, 

 are of common occurrence. It is utterly impossible to trace in- 

 dividual layers any distance, or to< identify any particular portion 

 of this member in a small exposure, except locally in the case of 

 some beds just above the fire clay, as noted in the preceding para- 

 graph. Lignite and pyrite are irregularly disseminated through 

 the entire mass, occurring in nearly every layer in at least small 

 quantities and forming a large part of some beds. Concretions 



