ORIGINAL ICE STRUCTURES PRESERVED IN UNCON- 

 SOLIDATED SANDS 



CHARLES P. BERKEY and JESSE E. HYDE 



The purpose of this paper is to describe and illustrate certain 

 structures occurring in unconsolidated sands of glacial origin. 

 These structures are so inconsistent with the usual behavior of 

 sands during accumulation that it is believed they point to special 

 conditions that could have prevailed only during the glacial epoch. 

 It may be that they give a clue to marginal structures within the 

 moving ice sheet itself. 



The deposit is located in New York City between 134th and 

 135th streets, west of Broadway. It may be seen from the River- 

 side viaduct which crosses the Manhattanville depression. It 

 appears as an irregular sand and gravel hill, probably only the 

 remnant of a once much more extensive deposit. While it has 

 been opened at several points to obtain building sand and abnor- 

 mal features are to be seen in several of them, recent excavation 

 for a building at the corner of 135th Street and Broadway has 

 revealed the most interesting exposures. 



With the exception to be noted, assortment of material is 

 excellent. Sands of a wide range in size are extensively repre- 

 sented, usually well assorted and plainly stratified. Rarely the 

 finer silts and clays occur in interstratified streaks. On the other 

 hand, some of the beds are made up of pebbles whose diameters 

 are measured in inches. On the whole the materials are coarse, 

 i.e., sands and gravels rather than silts and clays. The individual 

 layers are usually thin, a few inches only, but some of the finer- 

 grained beds may reach a foot or two in thickness. 



The exception to this rather thorough assortment of materials 

 is found in masses of bowlder clay which are intimately associated 

 with the other types. The bowlder-clay structure is very coarse. 

 Bowlders two or three feet through are not unusual and one over 

 six feet in diameter is closely associated with sand and gravel. 



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