CKOSSWICKS CLAYS AND HAZLET SANDS. 329 



typically occur, the first obtaining its name from the village of Cross- 

 wicks, upon Crosswicks creek, Burlington county, where the clays are well 

 developed and extensively worked, and the second from the town of 

 Hazlet, in Monmouth county, situated in the center of the sands, which 

 are well developed in the surrounding territory. 



Crosswicks clays. — These clays constitute the lower portion of the 

 Matawan formation in Monmouth, Middlesex, Mercer, Burlington, and 

 Camden counties. This lower division consists primarily of very dark 

 colored or black clays, which become at times slate or drab colored 

 toward the top, or, as in the vicinity of Matawan creek, interstratified 

 with layers of white sand. The dark clays are frequently quite glau- 

 conitic, but the glauconite is confined generally to thin seams and 

 pockets. This marly feature becomes less pronounced toward the upper 

 portion of the series and often entirely disappears. \These clays, partic- 

 ularly in the lower part, are quite unctuous when wet, but become more 

 and more brittle toward the top, while there is also a marked decrease 

 in the amount of iron sulphide. The Crosswicks clays are well exposed 

 upon the shores of Raritan bay and in the valle} r s of Matchaponix creek, 

 Crosswicks creek, Black creek, and other streams entering the Delaware 

 river. Toward the south the Crosswicks clays gradually become more 

 arenaceous and more micaceous and cannot be readily separated from 

 the overlying. deposits. 



Hazlet sands. — These sands comprise the upper portion of the Matawan 

 formation throughout the same area as the Crosswicks clays. This upper 

 division consists primarily of sands, highly ferruginous and brown in 

 color. in the lower portions and often affording indurated crusts. Above 

 this brown sand there is frequently found a well developed dark colored 

 clay, which is very much like the lower Crosswicks clays in many of its 

 characteristics, although oftentimes partaking to a considerable extent of 

 the micaceous features of the overlying sands. These upper sands, gen- 

 erally very micaceous and at times quite dark in color, are very persistent 

 at the top of the Matawan formation throughout the northern portion of 

 the district. They become more argillaceous and darker in color to the 

 southward and lose to a considerable extent their characteristic features. 



Toward the south the division of the Matawan into Crosswicks clays 

 and Hazlet sands becomes gradually obscured as the lower member be- 

 comes more and more arenaceous and micaceous, while the upper mem- 

 ber becomes more and more argillaceous, until finally in Gloucester and 

 Salem counties, New Jersey, the materials are practically identical and 

 consist of dark colored arenaceous clays, generally glauconitic and mica- 

 ceous. These features continue upon the south bank of the Delaware 

 river in the state of Delaware and throughout Maryland, but the glauco- 



