MINERAL RESOURCES OF THE STATE OF NEW YORK 49 



Farmingdale, Port Jefferson, Southold, Greenport and on Center 



island and Fishers island. 



On Staten Island Cretaceous clays, some of which are light in color, 

 occur in the southern section around Tottenville. They are too 

 siliceous, however, to be used in pottery, and have been employed in 

 terra cotta, fire brick, ornamental brick, etc. Stony clays of Pleisto- 

 cene age are found at Green Ridge and on the shore of Arthur kill, 

 where brick yards have been operated. 



Hudson valley. The valley of the Hudson from Mechanicville 

 south to Westchester and Rockland counties constitutes the great 

 brick-making region of the State and in fact the most important 

 district in the entire country. The clays are water-sorted glacial 

 materials, laid down in the Pleistocene flood valley known as Lake 

 Albany. They are found on either side of the river in terraces that 

 reach to an extreme elevation on the north of about 400 feet above 

 tide water and extend for a few hundred feet to several miles back 

 from the present channel. They are covered by a mantle of sand, 

 or occasionally of gravel, which was the last of the deposits in Lake 

 Albany. At the base they rest upon a water-bearing sand, imsorted 

 morainal materials or directly upon rock which is generally the 

 Hudson River shale. 



The clays attain a maximum thickness of 100 feet or somewhat 

 more. They are divided into layers or seams, with partings of fine 

 sand that is very similar to the sands overlying the beds. The sand 

 parting is usually scarcely more than a film, while the clay layers 

 themselves are often only a fraction of an inch thick. In a fresh 

 opening, as is supplied by the many banks where the clays are dug 

 for brickmaking, the layered appearance of the clays is very notice- 

 able on close examination, although it becomes obscured quickly by 

 exposure of the clays to the weather. The significance of the bedded 

 structure has not been explained, but it invites inquiry from the 

 standpoint of the possible relation to fluctuations in the supply of 

 sediment that may have been governed by seasonal or diurnal 

 changes, as suggested by the remarkable regularity in the succession 

 of clay and sand. 



The upper beds, representing a section of a few feet usually but 

 in some places as much as 30 feet, consist of brown or yellow clay 

 which has been shown by R. W. Jones^ to be the weathered and 

 leached eqtiivalent of the blue clay below. In comparison with the 

 latter the yellow clay contains smaller amounts of the more soluble 

 constitutents — calciiun, magnesiiun, sodium and potassitmi. The 

 two grades react somewhat differently to physical tests. The ordi- 

 ■ i.N. Y. State Mus. Bui. 178, p. 27. 



