in the Pleistocene and Post- Pleistocene. 15 



the results of certain hypotheses ? Such independent evidence 

 will now be considered. 



Woodworth has called attention to evidence that at some 

 time since the retreat of the ice the land has stood higher than 

 at present. South of Albany many of the tributaries appear 

 to be now filling up excavations below sea level which at 

 some previous time they had cut into post-glacial deposits.* 

 In the gorge of the lower Hudson River silt extends to 

 variable depths, 280 to 320 feet at New York City. At the 

 Storm King Crossing of the Hudson River, borings for the new 

 aqueduct encountered the highest stratum of bowlder beds at 

 a little over 200 feet in depth. These appear to be deposits 

 not excavated by river action since the ice retreated. The 

 evidence shows, therefore, that a stage of emergence has 

 occurred since the retreat of the ice but that this emergence 

 above present level was not over 200 feet as a maximum. It 

 may have been less. 



Evidence that a minor cycle of emergence and submergence 

 has occurred since the retreat of the ice is also found along the 

 shores of southern New England and the south. The submer- 

 gence to present level appears not to date back more than a few 

 thousand years at the most, as is shown by the extreme youth of 

 the shore line. Headlands have barely begun to be cut into, 

 embayments have only begun to be filled. Sediment carried 

 in by the tides forms salt marshes which are still flooded at 

 spring tides. Deltas at drowned river mouths have barely 

 begun to form. 



It happens, however, that near the margins of glaciation the 

 latest submergence has brought the present sea level only 

 slightly above that which existed at the beginning of the 

 retreat of the ice. The physical evidence for a rapid cycle of 

 post-glacial emergence of considerable amount, involving a 

 tract beyond the limits of glaciation, is therefore drowned and 

 the amount and importance of the emergence is perhaps best 

 given by the distribution of plants along the Atlantic shore 

 from New Jersey to Newfoundland. Britton, Hollick, and 

 others have discussed the significance of plant distribution, 

 especially of southern types of the Coastal Plain, but the most 

 important contribution on this subject has come from Fernald 

 in his analysis of the flora of Newfoundland. f He points out 

 that 118 species of plants belonging to the Pine Barren and 

 Coastal Plain floras of New Jersey and the south are known 

 from remote outlying stations along the coastal strip of New 

 England and the Maritime Provinces. Most striking, how- 

 ever, is the evidence from Newfoundland. He shows that 60 



* J. B. Woodworth, loc. cit., pp. 229-234, 1905. 



\ M. L. Fernald, A Botanical Expedition to Newfoundland and Southern 

 Labrador, Ehodora, vol. xiii, pp. 109-162, 1911. 



