284 H. L. FAlRCHiLb POST-GtAClAL SUfeMEItGENCE OF LOIs^G ISLANt) 



and by M. L. Fuller, in 1914, on the geology of the island (27), both 

 papers being Professional Papers of the United States Geological Survey. 

 Both of these writings held the view of subaerial glacial outwash for the 

 genesis of the plain, but without any adequate evidence or argument. It 

 was simply assumed without discussion as an element in their pliilosophy 

 of the complex history. It is somewhat surprising that the mass of facts 

 presented by such able men as Merrill, Eies, Davis, Darton, Salisbury, 

 and Woodworth should be entirely ignored, even though the evidence was 

 mainly at the west end of the island. P^dler admitted a depression of 20 

 feet on the New Jersey coast, but says it was not recorded on Long Island. 

 Since 1913 the writer has maintained the marine origin of the high 

 level terraces in the Hudson and Champlain valleys, and has shown in 

 maps the probable glacial depression of New York and New England. 

 The New England geologists have long recognized, but quite certainly 

 underestimated in amount, the Post-Glacial submergence of the Massa- 

 chusetts coast and the maritime provinces of Canada. The larger treat- 

 ment of this subject will have to include all the glaciated territory, for it 

 becomes more and more evident that the ice-cap weighted down the area 

 which it occupied. 



DESCRIPTJOisT OF THE PlAIN 



For a brief general description of the Long Island plain in its geologic 

 characters we can not do better than to quote from Salisbury (22, page 

 14), preceding his description of the plain by one of the Staten Island 

 lowland, similar in features and identical in origin to that of Long 

 Island. But it should be said that these descriptions do not apply to 

 the smooth plains with numerous kettles at the east end of the island. 



"Staten Island. — The considerable plain of stratified drift which skirts the 

 moraine of Staten Island on the south, between Fort Tompkins and Great 

 Kills, has a gentle slope seaward, and ends in a marsh which is shut in at the 

 south b3^ the beach ridge of recent origin. The greatest width of the plain, 

 near New Dorp, is about IV2 miles. The plain was contemporaneous in origin 

 with the terminal moraine, the materials of which it is composed having been 

 washed out from the edge of the ice when the moraine was being deposited. 

 At its moraine edge the plain is made up of coarse gravel, but with increas- 

 ing distance from the moraine the material becomes finer, grading off into 

 sand. The sand and gravel of the plain are often covered with chiy loam, so 

 that the coarser materials below are shown only in excavations. The depth of 

 the stratified drift is rmknown, but it is known to exceed 30 and 40 feet at 

 many points, and its base is therefore often below sealevel. 



"The plain is one which might give rise to various interpretations. It has 

 not the even slope away from the moraine which is characteristic of over- 

 wash plains. It is not unnsual for such plains to have some undulations near 

 their moraine edges ; but in this case the undulations are often conspicuous 



