CLAYS OF CRETACEOUS FORMATION. 173 



(80), and at several of the abandoned workings near the head of 

 Crossway brook. At other points the Amboy stoneware clay 

 rests upon clean, light-colored, quartz sand. So, also, the basal 

 portion is variable. At some banks a clean, quartz sand rests 

 upon the undulatory surface of the fire clay beneath. In other 

 banks or even in other parts of the same bank, a black sand or 

 sandy clay, or alternating layers of black sand and clay with a 

 maximum thickness of 1 5 feet occur between the fire clay and the 

 quartz sand. These beds are more or less lignitic, and Cook and 

 Smock 1 report finding numerous well-preserved leaf impressions 

 in some layers. Locally also, small masses, of amber are found 

 in these dark clays immediately above the fire clay. These dark, 

 sandy clays are best exposed at the J. R. Crossinan banks (65 and 

 66), J. R. Such's bank (67), and in several banks on the old E. F. 

 & J. M. Roberts property, north of Burt Creek, now owned by 

 Sayre & Fisher. 



Judging from the width of outcrop of this sand bed, where its 

 boundaries can be well determined, and assuming that its dip is 

 the same as that of the adjoining beds, 35 to 40 feet per mile, it 

 has a thickness of 45 to 50 feet. Exposures of 30 or even 40 feet 

 are not uncommon in some of the fire-clay banks near Sayreville 

 and Burt Creek. At Whitehead's clay pit (69) the base of the 

 sand has an elevation of about 38 feet above tide. Thence the 

 sand is apparently continuous to* a height of 90 feet near the crest 

 of the hill just east of the pit. This thickness (52 feet) agrees 

 fairly well with that estimated from the dip, when the irregular 

 character both of the upper and lower beds of clay are considered. 

 Fifty feet seems a fair measure of the thickness of this member 

 where both the adjoining clay beds are moderately well developed. 



SOUTH AMBOY FIRE CLAY. 



The South Amboy fire-clay bed lies beneath the quartz sand 

 bed just described. Its main outcrop is on the northern and west- 

 ern slope of the high hills, which lie south of the Raritan river 



1 Clay Report of 1878, p. 69. 



