8 BULLETIN 159, TJ. S. DEPARTMENT OF AGRICULTURE. 



Even the streams considerably to the south of the region directly 

 affected by glaciation were considerably swollen and their courses 

 were blocked by river ice during portions of the year. This gave 

 rise to the transportation of considerable amounts of coarse gravel, 

 and even of stones of large size, which were carried in floating ice. 

 When the ice melted along the coast or in the estuarine waters this 

 coarser material was mingled with the finer grained sediments 

 brought under normal conditions of erosion and transportation. Thus 

 the Pleistocene sediments along the margin of the glaciated region, 

 and even to a considerable distance to the south, have been directly 

 or indirectly influenced by the glaciation of the more northern region. 



Long Island, X. Y., lies within that portion of the region which 

 was directly invaded by the ice during the glacial period. 1 As a 

 result all of the older formations were overridden by the sheet of 

 glacial ice, which advanced at one time as far south as the line of 

 hills that extends from the vicinity of Westbury to Montauk Point. 

 These hills represent the deposition of material as a terminal moraine 

 while the ice stood along this line. Later the glacial ice receded and 

 then readvanced to a position along the more northern belt of hilly 

 territory, which follows the northern shore of the island, where addi- 

 tional morainal material was deposited. At the time of this halting 

 there was spread out over all of the southern portion of the island the 

 thin sheet of gravelly, sandy, and loamy material which constitutes 

 the present surface of the land. The sloping plains which intervene 

 between the two lines of morainal hills and which sink below the 

 water level along the southern shore of the island were formed at 

 that time by the deposition of material partly transported by the ice 

 from mainland to the north and partly derived from the older for- 

 mations, which formed the surface upon which the ice rested. 



A large part of this deposition took the form of cross-bedded sands 

 and gravels and of rather coarse sand, washed out by water from the 

 melting ice. Where these coarser materials form the present land 

 surface they give rise to the areas of Sassafras sand as mapped upon 

 the western end of Long Island. The higher, interior plain and a 

 large part of the marginal plain which intervenes between the north- 

 ern hills and the south shore west of Farmingdale are occupied by 

 a gravelly silty loam formed at a late stage of the deposition of this 

 material. This gives rise to the extensive areas of the Sassafras 

 gravelly loam mapped there. Small areas of loamy material were 

 deposited immediately to the West of Jamaica Bay. This forms the 

 Sassafras loam. A large part of the material built into these deposits 

 is undoubtedly of direct glacial origin. 



1 Professional Paper No. 82, U. S. Geol. Survey. The Geology of Long Island, N. T., 

 by M. L. Fuller. 



