THE POST-PLEISTOCENE CLAYS. 121 



At Hand & Son's yard (236), North Plainfield, a sticky clay 

 7 feet thick is used. The clay grades downward into fine sand 

 of glacial derivation. Beneath the sand (7 ft.) is the red shale 

 of the Newark formation. The clay occurs in a slight depres- 

 sion, adjoining a tributary to Green brook, and is perhaps a 

 flood plain and wash deposit of post-Glacial ag-e. It may, how- 

 ever, be connected in origin with the closing stage of the Glacial 

 period, and so more properly belong" under the head of glacial 

 clays. Near its borders, where it adjoins a much older gravel 

 formation at a slightly higher level, pebbles from the latter are 

 mixed with it 



At Benward's brickyard. Brass Castle, Warren county (279), 

 a sandy, gritty clay containing numerous partially disintegrated 

 bowlders of gneiss, and derived by wash from the steep hillside 

 adjoining, is used in a small way for the manufacture of com- 

 mon brick. A clay formed in a similar manner, but of better' 

 quality, is found at Flemington (276), at Pedrick's yard. It is 

 from 3 to 7 feet thick, and rests upon the red Triassic shale. 

 The lower portion of the clay is simply the weathered part of 

 the shale and contains minute shale bits. The upper 4 feet is 

 yellowish in color, contains minute bits of partially decomposed 

 trap rock, as well as some larger fragments of the same rock, and 

 is evidently the result of wash from a steep hill of trap* a few 

 rods west of the yard. 



Clay loams. 1 — At many points in the State there are clay 

 loams, which are used by themselves or in combination with 

 other clays. They occur at all elevations up to 200 feet and 

 more. They are by no means continuous, even within the areas 

 in which they occur, and not infrequently they are so poorly 

 defined as to be indistinguishable from the weathered products of 

 the formations on which they rest. They sometimes occur, how- 

 ever, in such relations, and have such a composition that they 

 cannot be regarded as a part of the underlying formation, nor 

 as the product of local wash, nor as a wind deposit. Their 

 average thickness is 4 or 5 feet ; they rarely exceed 8 feet, 

 although thicknesses of 20 feet are not unknown. They are com- 



1 Geol. Surv. of N. J., Vol. V, Report on Glacial Geology, pp. 206-210. 



