386 p. S. MARTIN 



B.P., represented a period of stagnation and retreat, with several 

 climatic reversals and readvances of ice. Pollen records are still 

 scattered, and dated diagrams are not as abundant as we might 

 wish. However, they begin to approach in detail those available for 

 Postglacial time. The stratigraphic break between the Postglacial 

 and Late-glacial, which generally marks a rise in organic sedimenta- 

 tion, is a convenient level for a radiocarbon date. Partly for this 

 reason, I have found it possible to assemble sufficient dated pollen 

 horizons to attempt a vegetation map for the end of the Late-glacial 

 during the Valders readvance. Even though ice returned to central 

 Michigan, considerable climatic improvement is indicated over the 

 Full-glacial conditions. In northern New England Deevey's dis- 

 covery of Valders tundra is confirmed by Livingstone (see Table I). 

 C^^ dating of pollen zone A-4 in Connecticut indicates the presence 

 of boreal forest rather than taiga or tundra. The Valders readvance 

 did not affect radically the forests of southern New England. 



Mixed hardwoods and conifers, including spruce, occupied Glade 

 Bog (2,700 feet) in Tennessee (Johnson, personal correspondence). 

 Pine-spruce-birch-hemlock dominated the Cranberry Glades of West 

 Virginia (3,400 feet). Alpine tundra had retreated or perhaps en- 

 tirely disappeared from the southern Appalachians. Small ice fields, 

 almost certainly surrounded by tundra, excavated circs in the 

 Catskills, Adirondacks, and other high mountains of New England 

 (Manley, 1955). Perhaps of greatest interest is the evidence from 

 pollen studies that mixed deciduous forest had replaced the pine- 

 spruce forest of the Carolina Coastal Plain (Frey, 1953). The Valders 

 forests of that area supported mesophytes such as beech and hem- 

 lock, temperate species no longer part of the regional pollen rain. 



West of the Appalachians the situation is less clear. Andersen 

 (1954) considered a typical Late-glacial profile from the George 

 Reserve in southern Michigan to be of Younger Dryas age (Valders 

 as currently understood in North America). However, if the C^^ dates 

 from the George Reserve (M-223, M-224, each 11,450±600 B.P.) 

 are from the same core as was used in Andersen's study, his NAP 

 zone is older. Possibly it represents the Older Dryas (Port Huron) 

 period. Andersen presented a thoughtful and skilled analysis of the 

 problem of "rebedded" and "redeposited" pollen in Late-glacial 

 sediments and made a strong case for allochthonous origin of such 

 temperate genera as oak, sweet gum, and ash. The regional pollen 



