CLAYS OF CRETACEOUS FORMATION. 161 



where the contrast is, if anything, more definite than in Mon- 

 mouth county. 



The thickness of Clay Marl I increases slightly from north- 

 east to southwest. In Monmouth county its thickness is about 

 35 feet, at Bordentown it is 60 feet, and in Salem county about 

 the same. Its outcrop across the State is shown on Plate X, and 

 more in detail for the Matawan region on Plate XII. 



Localities. — Ait the present time Clay Marl I is used wholly or 

 in part at the following places : Edward Farry, Matawan (228) ; 

 Pennsylvania Clay Company, Matawan (226) ; Dunlap & Lisk, 

 Matawan (230) ; Reed Brothers, Hightstown (193) ; The Bor- 

 dentown Brick Company, Bordentown (109) ; Murrill Dobbins, 

 Kinkora (113); Augustus Reeve, Maple Shade (149), and 

 Budd Brothers, Camden (143). The results of tests upon sam- 

 ples of this bed and those from other localities are given in Chap- 

 ters XVIII and XIX. 



THE RARITAN CLAY SERIES. 



Character. — The Raritan or Plastic Clay series, as it was called 

 by Dr. Cook, is the lowest and oldest of the three divisions of 

 the Cretaceous in New Jersey. It consists of a number of beds 

 of clay, sand, and locally, of gravel. The clays are of various 

 kinds, from nearly white or steel-blue fire clay of the highest 

 grade to black, sandy clay, containing varying amounts of pyrite 

 and sulphur, and used only for common brick. Some of the 

 sands are nearly pure quartz, sharp and angular in grain, suitable 

 for a high grade of fire sand; others are highly micaceous, or lig- 

 nitic, or arkose. Some of the latter, composed of coarse grains, 

 or even pebbles of quartz and decomposed feldspar crystals, form 

 the beds of so-called "feldspar" used in the manufacture of fire 

 brick. Along the Delaware river, beds of gravel and cobble 

 stones are known to occur locally, but in Middlesex county noth- 

 ing larger than very coarse (pea) sand has been seen. 



The Raritan series is characterized by the rapid alternation 

 of strata, the abrupt transition both vertically and horizontally 

 from one to another of these beds, and by the absence of any 

 11 a g 



