PLEISTOCENE GEOLOGY OF NASSAU CO. AND BOROUGH OF QUEENS 645 



Yellow and yellowish gravels occur in some of the railway cuts, but 

 it has not been possible in the present survey satisfactorily to delimit 

 such older deposits, except in one case, that of the Far Rockaway 

 ridge. This peculiar deposit is described on p. 651. 



The materials exhibit at surface a gradual diminution in coarse- 

 ness from coarse gravel near the inner moraine to fine sands at the 

 outer limits of the plain. A shallow excavation in the county 

 building site at Mineola exhibited alternating layers of coarse, nut- 

 sized gravel and fine sandy gravel with feebly developed crossbeds 

 at intervals. The pebbles were mostly white quartz and gneiss, 

 this latter often decayed. More rarely were seen small pebbles of 

 ironstone and a ferruginous conglomerate of white cpiartz pebbles. 

 Pebbles as large as 3 inches in diameter were extremely rare. 



A rather anomalous element for the npper part of the section of 

 the plain is the brick clay found at East Williston. While clays 

 would normally develop about the margin of a plain of this char- 

 acter in the sea, to be subsequently overlain by the outward growth 

 of the thickening plain, such clays would hardly be formed with a 

 surface so nearly that of the completed gravel plain ; and it is prob- 

 able that these are either an older degraded deposit or owe their 

 position to the deformation and uplift of the basement on which the 

 deposits and topography of the last extraglacial streams have been 

 imposed. The section, which is exposed in a somewhat depressed, 

 troughlike area, is as follows : 



SECTION OF CLAYS AT EAST WILLISTON 



Feet 



Soils... , 1.5 



Sand, gravelly, with quartz and granitic pebbles, locally red- 1 

 dened L 



Clays, sandy, with quartz pebbles 



Clay, sandy in yellow band 



Clay, blue, finely laminate, rarely with quartz pebbles, 



exposed ^ 



The section is apparently conformable throughout. Crosby, if I 



understand him rightly, would refer these clays to the Tertiary. 

 The manner in which the water percolating through the sand 



plain north of and above the 60 foot contour in the Hempstead 



8 



