CLAYS OF CRETACEOUS FORMATION. 177 



clay varies from 9 to 17 feet in thickness, and is mostly red or 

 red-mottled, instead of white. The same bed has also been opened 

 at other places, as indicated on the map, Plate XL 



Owing- to the extreme variations in the thickness of this clay 

 bed and its entire absence locally, it is difficult to map it accurately. 

 Yet on the basis of its dip, which is about 40 feet per mile, its 

 probable position has been approximately determined. 



THE FELDSPAR KAOEIN SAND BED. 



Beneath the South Amboy fire-clay bed and above the Wood- 

 bridge clays, there is an assemblage of beds, mostly sand, of vary- 

 ing texture and order of stratification. Here are included the 

 so-called "feldspar" and "kaolin," as well as beds of loose quartz 

 sand, thin clay lenses and layers of fine, white, micaceous sand. 



The upper portion of this member has been explored by a num- 

 ber of borings in the bottom of the Amboy fire-clay pits, while 

 the middle and lower parts are shown at the top of some of the 

 excavations in the higher portions of the Woodbridge clays and 

 in the "feldspar" banks. That there is great variation in the 

 order of stratification, and that the so-called "feldspar" and 

 "kaolin" beds do not occupy definite stratigraphical horizons is 

 soon apparent upon examination in the field, and may be readily 

 seen from the following sections. 



At McHose Brothers' pit (45) a boring gave the following sec- 

 tion beneath the fire clay : 



A Boring at McHose Brothers' Clay Pit. 



a. Red sand, 6 ft. 



b. "Feldspar," 4 " 



c. Fine sand, some clay seams, 20 " 



30 ft. 



Another boring 1 made years ago* in J. H. Manning's banks (38) 

 showed below the fire clay : 



1 Report on the Clays of New Jersey, 1878, p. 132. 

 12 CE G 



