8 ICE RECESSION IN NEW ENGLAND 



Long Island Sound a Lake 



The absence of a barrier off the clay marshes at New Haven 

 seems to show that Long Island Sound in late glacial time was 

 separated from the sea and held a lake. The ponding of a lake 

 with a level of about 40 feet (Dana, 1870, p. 66) above present 

 sea level at New Haven evidently signifies that the threshold 

 separating the basin from the sea stood at the same altitude. 

 The sill at the present time between Long Island and Fisher's 

 Island, just southwest of Fisher's Island, rises to within 210 feet 

 of the surface of the sea. To what extent the original, late 

 glacial threshold has been cut deeper cannot be said, but 50 to 

 60 feet seem likely, judging from the chart. The original sill, 

 then, should now lie at a depth of about 150 feet, and the level 

 of the glacial lake should incline from 40 feet above sea level 

 at New Haven to about 150 feet below it on the threshold. 

 The distance from New Haven straight south to the shore 

 of Long Island, which lies in about the same relation to New 

 Haven as does the threshold, is twenty-three miles. The in- 

 clination under these conditions should be about 8 feet to the 

 mile. 



Rising of Peripheral Land Following on Recession 

 of Ice, and Subsequent Sinking 



At New Haven the writer measured 200 varves and at Hacken- 

 sack 400, the measured horizons only representing parts of the 

 clay beds. At Hackensack there are surely more than 1,000 

 varves, probably many more. The existence of the barrier of 

 the lakes for so long a time indicates that the region, at the 

 release of the ice, did not stand in its highest position but took 

 it when the ice front was farther away. As the land rose the 

 barriers were cut down. Since little erosion may have occurred 

 below the level of the sea, eastern Long Island may have reached 

 a level about 185 feet higher than the present. The conditions 

 in southern New England were much the same as in the Baltic 

 region in late glacial time (Antevs, 1922). At the release of the 



