CLAYS OF CRETACEOUS FORMATION. 155 



towards the top of the shell layer. Immediately above the latter 

 lie the workable gTeensand marl beds. The shells occur some- 

 what sparingly in the sand for some distance below the fossil 

 bed and more rarely individuals occur in the marl above. Inas- 

 much as this layer is a very persistent feature and can be readily 

 recognized at many localities across the State, and since the beds 

 above and below are so> different in character, the top of the Clay 

 Marl series is a definite and easily recognizable horizon. 



The Wenonah sand (Clay Marl V) outcrops along the south- 

 eastern side of the Clay Marl belt from Atlantic Highlands to 

 Salem county. It is in part covered by areas of Pensauken 

 gravel, but it forms the surface deposit over considerable tracts 

 in the vicinity of Sharptown, Salem county; over a broad belt 

 between Mullica Hill and Swedesboro, near Chew's Landing; 

 Wenonah. east of Haddonfield, and near Evesboro, in Burlington 

 county. In Monmouth county it forms the sandy belt on the 

 northwest of the Lower Marl from Tennants, Robertsville, and 

 Morganville to Atlantic Highlands. Its thickness is about 50 

 to 55 feet in Monmouth county, increasing to something over 

 60 feet in Salem county. , 



Although locally it contains thin seams of clay, yet these are 

 nowhere of economic value. 



CLAY MARL IV ( MARSH ALLTOWN BED). 



This member of the Clay Marl series is more variable in its 

 make up than either of the other four, but the variations are grad- 

 ual, and there is no difficulty in tracing them from one phase to 

 another. It ranges from a sandy clay to a clayey marl, which at 

 one time was mistaken by all geological workers in the State for 

 the Lower Marl. 1 In Monmouth county it is chiefly a laminated, 

 micaceous clay with thin seams of sand, which locally may be 

 of some commercial importance. In this region greensand grains 

 are wanting in all save the upper portion, in which they are only 



1 Mr. Knapp was the first to differentiate it from the Lower Marl and 

 make out its true position, although he did not receive proper credit for it in 

 the Annual Report for 1897. — H. B. K. 



