Outwash plain 



Terminal moraine 



Figure 5. Origins of glacial kettle and outwash wet- 

 lands. Conditions close to the margin of an almost 

 stagnant ice sheet are shown diagrammatically in the 

 upper block diagram. The lower diagram shows the 

 same area after the ice is entirely gone. Cedar forests 

 develop in kettles and along outwash channels 

 (adapted from Strahler 1966). 



1.4.2 Establishment and Survival 



Since the beginning of the current in- 

 terglacial period, the long-term overall rise in sea 

 level, averaging about one mm per year due to glacial 

 melting and land subsidence, has played an impor- 

 tant role in the development of many cedar wetlands. 

 A. Redfield, (1 965) in the context of a rising sea level, 

 proposed a model for the development of coastal salt 

 marshes, which he extended to the development of 

 coastal freshwater swamps (A. Redfield, pers. 

 comm.). Redfield noted that near the seacoast, the 

 rising sea level more or less keeps pace with peat ac- 

 cumulation lifting the lens of freshwater above it. 

 The effect of the rise in ground-water levels is that ex- 

 isting wetlands remain wet, promoting the contin- 

 uous presence of some cedar swamps for as much 

 as 6,800 years (Belling 1977). 



Along the coast, seawater inundated fresh- 

 water wetlands, giving rise to the accumulation of 

 layers of saltmarsh peat superimposed on freshwater 

 peat. Ample macrofossil evidence of the killing of 

 cedar forests by saline incursion is found all along the 



I Block diagrams, very large vertical exaggeration I 



Uplands 

 N.- 



NET DEPOSITION 



/ 

 ''Alluvial tan 

 o( tributary 



Figure 6. Origins of backswamp cedar wetlands, (a) 

 When sea level was below the present position, the 

 river trenched its valley (b) As sea level rose, glacial 

 meltwater poured down the river, creating a braided 

 stream choked with sand and gravel, (c) Deposits of 

 today's meandering river, established at a yet higher 

 sea-level position, have buried the older braided 

 stream deposits. Cedar wetlands develop in back- 

 swamps and along small streambanks (adapted 

 from Long 1974). 



Atlantic seaboard (Figure 7). Atlantic white cedar 

 trunks, sometimes in the same position as in life or 

 as they fell hundreds of years earlier, may be seen at 

 low tides below saltmarsh turf on the coasts of New 

 Hampshire, Massachusetts, New Jersey, Virginia, 

 and elsewhere (Bartlett 1909; Heusser 1949, 1963; 

 Belling 1977), and buried deep in off-shore marine 

 sediments (Redfield and Rubin 1962). 



