294 H. L. FAIRCHILD POST-GLACIAL SUBMERGENCE OF LONG ISLAND 



noted, with more or less clearness, at many points where the moraines 

 stood in water and were exposed to wave-work. Where the moraines were 

 faced by heavy outwash deposits the beach phenomena are less evident. 

 Good localities are northwest of Eastport, north of East Quogne, and 

 particularly northwest of Bridgeliampton. These localities are all on the 

 south face of the earlier (southern) moraine. The writer has not exam- 

 ined the northern moraine, but the topographic maps suggest many places 

 \vhere the shoreline ma}' be seen distinctl}'. In the eastern half of the 

 island the moraines were laid down largely beneath the sea, and the ma- 

 rine shore is usually distinct against the rough, forest-covered hills which 

 stood above the waters and exposed to the waves. 



The uniform, smooth, horizontal contact of the sand-plain against the 

 steep, rough faces of the moraines can not be explained except as the 

 work of waves. It is as good evidence of a shoreline as are bars or cliffs. 



An important fact in this connection is that these shores, from Staten 

 Island to Bridgeliampton, rise steadily eastward at about 1.25 feet per 

 mile, and that they agree very closely with the theoretic marine plane 

 indicated in the map. It should be emphasized that the isobasal lines 

 were projected across Long Island without any reference to its geology 

 and before any study was made of the submergence phenomena. 



SMOOTHNESS OF THE PLAIN 



The very smooth and even surface of the whole southern plain and the 

 extreme flatness of large areas, specially the south and east portions, 

 would seem to be very strong suggestion, if not actual proof, of sub- 

 aqueous origin; but the two more recent and exhaustive papers refer 

 the plain, with scant discussion, to subaerial outA\'ash. The work of 

 Veatch and others (25) dismisses the subject of the genesis of the plain 

 with a single sentence (page 45), and says that after the removal of the 

 latest ice-sheet the land stood somewhat above its present level (page 48). 

 Fuller (27) also assumes subaerial origm, and endeavors to explain how 

 the "outwash fans'^ could unite to produce the flat plains (-pages 36-37). 



Quoting again from. AYatson (2, page 443) : 



"The surface of this immense plain (Farmingdale to Riverheacl) is so nearly 

 level, with onlj^ trifling undulations, that the eye can detect no declension. 

 From the ridge to the ocean thei-e is a gradual hut imperceptible descent." 



The south border of the plain, within a few miles of tide water, car- 

 ries numerous living streams in poorly defined valleys, the lower stretches 

 apparently drowned as if by recent sinking in small amount. The soils 

 of this belt are more clayey than the ground fartlier north and more 

 subject to present erosion. 



