CLAYS OF CRETACEOUS FORMATION. 157 



beaches, yet not infrequently it contains thin laminae of firm 

 brittle clay, which stand in sharp contrast to> the adjoining- sands, 

 there .being- absolutely no gradation between the two: The clay 

 laminae contain no sand or grit, and the sand layers are entirely 

 free from clay. 



Towards the upper portion of the formation there is a horizon 

 at which a bed of clay occurs locally. The clay is apparently not 

 continuous, but has been seen at a number of widely separated 

 points. At a few points this clay lense has been utilized for the 

 manufacture of common brick, but nowhere extensively, and it 

 is not likely ever to be of more than local importance. At the 

 present time it is worked, in a small way, only at Thackara's pits, 

 near "Woodbury (155). 



This member of the Clay Marl series is thickest at the north- 

 east and decreases gradually towards the southwest. In Mon- 

 mouth county it has a thickness of over 100 feet, on Cross wick's 

 creek it has diminished to 30 or 35 feet, and at Swedesboro it 

 hardly exceeds 20 feet. Farther southwest it seems to pinch, out. 

 Its characteristics, however, are the same where it is thin as where 

 it is thick, and it retains its integrity as a distinct bed, so> that 

 it is readily recognizable everywhere from Atlantic Highlands to 

 Salem county. It does not become more clayey to< the southwest, 

 as has been sometimes asserted, 1 but retains its characteristics 

 unchanged. 



It passes upward by a somewhat rapid transition into' the 

 overlying glauconitic or sandy clay, so that its upward limit can 

 be well enough defined for purposes of mapping. It is underlain 

 by a well-defined clay bed, into which it passes more or less 

 sharply, so that as a formation it is distinct, It outcrops in ap- 

 proximately the middle of the Clay Marl belt, just to the south- 

 east of the clays indicated on Plate X. 



CLAY MARL II (WOODBURY). 



Character. — The sand member just described is underlain by 

 a thick bed of black clay, which we have designated as Clay Marl 



1 Clark, W. B. Ann. Rep. 1897, p. 179. 



