GLACIAL AND POST-GLACIAL HISTORY 619 



plains or plateaus, some of them heading in kames and others with 

 ice-molded but kameless sources, which is found from the latitude 

 of Hackensack and Englewood nearly to the northern border of the 

 state. The deposits of the ice-waters are also marked by the clay 

 which is found underneath the gravel and sand in the southern part 

 of these lowlands, or spread out with little overlying sand or gravel, 

 and which has thicknesses from 100 feet or less, to 215 feet.' 



That the water body in which these deposits accumulated may 

 have been separated from, and perhaps was slightly higher than 

 the Hudson water body wih be shown later (p. 645). It is to be noted 

 that the accumulations marking the successive positions of the ice- 

 edge on the higher land are not traceable across the lowlands occupied 

 by this water body, at least not to the same extent, either in number or 

 continuity, as on the higher land. 



In the Hudson Valley the deposits marking the successive positions 

 of the ice-edge do not have notable development south of Sing Sing, 

 but from a httle north of this place to north of Glens Falls, and beyond 

 into the Champlain Valley, there is a succession of deposits, described 

 above (pp. 430 S.), which, it is beheved, mark its successive positions. 

 As the ice retreated northward, the ice-front appears to have assumed 

 two distinct phases in different parts of the valley. 



Phase I. — In those parts of the valley (notably the narrower parts) 

 where the gravel plateaus are marked either by morainic phenomena 

 or by irregularities of similar import at the edge next to the Hudson, 

 or by higher elevation next to the Hudson and lower next to the 

 valley wall, and with layers dipping toward the valley wall and south- 

 ward, it is believed that the ice protruded down the valley, and that 

 the accumulations took place at the edge of this ice-tongue, or between 



I See Annual Report of the State Geologist of New Jersey for 1903, pp. 195-210, 

 and Final Report, Vol. V, pp. 506-13, 595-628, 632-42. At the time this report was 

 written three hypotheses were suggested to explain the form of these higher gravel 

 plains and plateaus; namely, (i) that they were accumulated in a water body, either 

 a lake or an arm of the sea; (2) that they had received their form from stagnant ice- 

 masses; (3) that both co-operated. In the absence of wave-wrought features, and 

 in the absence of exposures, the junior author preferred to leave open the question of 

 the origin of these features, where the structure was unknown, although at this time, 

 and for some time before, it had been recognized that a water body existed in the 

 Hudson Valley as the ice was retiring, and that both ice and water body had been 

 influential in producing the forms there found. 



