280 H. L. FAIRCHILD POST-GLACIAL SUBMERGENCE OF LONG ISLANL) 



rent ice-sheets, and much remains to be determined with reference to 

 correlation of strata, the origin of the island, the amount of Pleistocene 

 movement, and the genesis of the topography. 



The most conspicnons topographic features of the island, Avhich have 

 naturally received most attention, are the belts of morainic hills. But 

 quite as interesting anrl of equal significance are the extensive sand- 

 plains, equivocal in their origin. The present paper will present the 

 facts which prove that the southern and the eastern plains were formed 

 as a submerged marine plain. The bearing of some of the phenomena 

 on the genesis of the plain has not been recognized and the many evi- 

 dences of submergence have never been assembled. 



The writer's interest in Long Island is not simply because the area 

 has had a salt-water bath, but because the submergence was part of the 

 fery recent diastrophic movement of northeastern America, which has 

 not been recognized in its full value. 



This paper is not an argument against any apparently contradictory 

 facts nor against any preponderance of opinion or weight of authority, 

 because no facts to disprove Post-Glacial submergence have been pre- 

 sented, and the weight of geologic opinion favors at least some lower 

 attitude than the present. It is true that a fcM^ recent writers have as- 

 sumed or asserted an elevated attitude of the island when the latest 

 deposits were made, but without meeting the positive evidence presented 

 ;^y earlier writers of the lower attitude of at least the west end of the 

 island and without making any allowance for the depressing effect of the 

 weight of the latest ice-body. It is unnecessary to enter into any discus- 

 gion of the very complex history and involved glacial deposits as postu- 

 lated by Veatch (25) and Fuller (27), for the evidence of Post- Wiscon- 

 sin submergence can stand alone. 



Although it is here claimed that the combination of characters in the 

 plains can be fully explained only by the theory of immersion, the proofs 

 of Post-Glacial submergence of Long Island, to the extent indicated in 

 the map (plate 10), which are relied on in this writing, are quite inde- 

 pendent of the characters of the plains in the central and western parts 

 of the island. The convincing evidence of the submergence is found in 

 the combination of elements and features which have been overlooked or 

 their significance not recognized in this connection. Tbese are (1) the fact 

 that the island lies well within the area of Post-Glacial depression; (2) 

 the positive evidence of deep submergence of the near-by Hudson Valley 

 and the Connecticut Valley (28) : (3) the subdued, wave-washed surface 

 of the moraines below the theoretic plane, and tlie very rough, harsh, 

 Uiisubdued aspect of the mgraines above that plane; (4) the presence of 



