,'^06 H. t. FAiRCHlLD 1>0ST-GLACTAL SUfeMEfeGENCE OF tONG ISLANt) 



line between the subaerial ontwash and the suboceanic plain is located 

 somewhat arbitrarily in accord with the theoretic altitude of the marine 

 plain. But where the sand-plain abuts against the rough moraines, with 

 no intervening outwash, the shore is clear and surprisingly accords with 

 the theoretic level. These sliores are indicated by solid lines, as seen at 

 Farmingdale and north of Bridgehampton. Future study will probably 

 find a general accordance everywhere. 



The southward limit of the kettle areas is shown by a hachured line. 

 The ice-front certainly reached to this line and perhaps farther. 



Summary 



The partial submergence of Long Island under the weight of the ice- 

 sheet was predicated from the position of the isobases connecting points 

 of equal submergence in New York and Connecticut. Examination of 

 the surficial features of the island confirms the prediction. 



The earlier writers recognized the marine origin of the plain, and 

 Messrs. Darton, Davis, Merrill, Eies, and Salisbury published super- 

 abundant evidence of deep submergence of the New York City district 

 and the Hudson Valley. 



It is found that direct proofs on the island of submergence equal in 

 amount to that indicated by the isobasal lines are abundant and even 

 conspicuous. These are: (1) Conspicuous shores where the sand-plain 

 abuts against the high and rough moraines; (2) the smooth surfaces of 

 the plain; (3) the composition of the lower plain and its loamy super- 

 ficial soil; (4) the subdued character of the moraines which lie beneath 

 the theoretic plain; (5) wave-leveled morainic tracts, indicated by the 

 many and large kettles; (6) stratified sands in open valleys, with in- 

 cluded boulders; (7) terraces and delta plains north of the moraines at 

 the theoretic height; (8) the submergence of neighboring territory, the 

 Hudson and Connecticut valleys, and (9) the accumulating evidence 

 that the Labra dorian ice-body weighted down all its buried territory, 

 and that Long Island was well within that area. 



The greater plain of the west half of the island is found to have dual 

 character, some limited and higher portions being subaerial glacial out- 

 wash, with no clear line of demarkation from the subaqueous plain. 



The altitudes of the shorelines and the uniform slant of the water- 

 produced features is in good agreement with the theoretic marine plain. 

 This rises from about 60 feet at Brookl3^n to about 160 feet on the mo- 

 raine north of Bridgehampton. 



The lack of beaches (bars, spits, etcetera) is shown, by many examples 

 of such deficiency on strong shorelines, to have no negative value. The 



