



r ♦■ 



40 



AGE.y 



80 120 



160 



200 



e 10 

 u 



o 

 « 



a. 

 a) 

 O 



20 - 



30 



Smoothed Tide Gage Record 



Salt Marstt Pb 



210 



Record — 





/ 



/ 



/ 



/ 



.-.•? 



YEAR 



Figure 2. Variation in apparent sea level at New York City as shown by a 

 smoothed tide gauge record and the elevation of a Spartina patens marsh in New 

 Haven, Connecticut, calculated from the distribution of Pb-^iU in the sediment 

 (McCaffrey 1977). 



regimes are very different in the two 

 areas. Harrison and Bloom (1977) 

 found a positive correlation between 

 tidal range and accretion rates in 

 Connecticut marshes; Baumann (1980) 

 found greatest sedimentation in 

 Louisiana marshes during winter, when 

 the wetlands were innundated for less 

 time than they were during summer. 



The second 

 marsh-building 

 recently by 

 (1980), who 

 development in 

 States has been episodic 

 last 10,000 years, taking 



explanation for past 



has been developed 



Rampino and Sanders 



suggested that marsh 



the Northeastern United 



during the 



place only 



when relative sea level remained 

 constant for a time or went through a 

 transient lowering in response to 

 shorter-term climatic events. Sea 

 level has risen over the past 15,000 

 years with different average rates of 



increase for different time increments 

 (Figure 1). These data and other 

 information have also been interpreted 

 as showing oscillations in sea level, 

 and the available information is 

 apparently not detailed enough now to 

 resolve the question. On the basis 

 of ^^C-dated peat samples from the 

 inner continental shelf, Rampino and 

 Sanders (1980) concluded that there 

 were six previous periods of marsh 

 growth about 1,000 years apart, the 

 most recent of which began some 4,700 

 years ago. 



Changes in relative sea level 

 (see Figure 1 and Table 1) are thought 

 to reflect two components: isostatic 

 processes that raise or lower the land 

 surface and eustatic processes due to 

 changes in the volume of the ocean 

 from glacier formation and melting. 

 The relative contribution of these 



