Identification of the plant remains recovered from the basal peat and the 

 overlying human occupational zones, dated respectively at 5700 ± 700 yrs B.P. 

 and 4500- 130 yrs B.P., indicates that climatic conditions were essentially 

 comparable with those of the present. There is some cogent evidence, based 

 on statistical representation of certain species, that the climate at the time of 

 human occupation and construction of the Fish Weir was warmer than the present. 



An interesting and significant corollary to the sedimentary history and 

 chronological interpretation of the Boston Back Bay sediments has recently 

 been secured from studies in the Barnstable Marsh, a large salt marsh on the 

 northern coast of central Cape Cod, Massachusetts. Extensive unpublished 

 palynological studies by Patrick Butler, formerly a graduate student in Harvard 

 University now deceased, showed that the plant remains of the marsh consisted 

 almost exclusively of Spartina alterniflora and S. patens . A depth of Z9 feet of 

 salt marsh peat was encountered in the deepest boring. Detailed pollen diagrams 

 were constructed from several cores. The entire marsh deposition was directly 

 controlled by the advancing tidal plane. Recently Dr. Meyer Rubin of the U. S. 

 Geological Survey secured four carbon- 14 dates from Barnstable Marsh sannples 

 submitted by Dr. A. C. Redfield. There are as follows, respectively with 

 depth and age, 21 t 6 inches - 400 ± 100 yrs B.P.; 33 inches I 770 ± 100 yrs 

 B.P. ; Z07 inches z 1880 ± 100 yrs B.P, ; 327 inches z 548O ± 120 yrs B.P. 

 Since the present surface of the marsh is close to the mean high water tide 

 range it is apparent that the salt marsh accumulation represents an average 

 rate of submergence of approximately 6 inches per century, a value remarkably 

 close to that for the Boston Basin area sixty miles away, as recorded in the 

 Boylston St. Fish Weir site. The data, although regrettably limited, would 

 also show that the rate of submergence has not been uniform during the period 

 of marsh development. From neither the Boston deposits, nor the Barnstable 

 Marsh deposits is it possible to conclude that submergence has resulted from 

 crustal downwarping or from eustatic sea level rise. 



DISCUSSION 



R dfi Id' ^ would like to make just one comment with regard to the sort 



of evidence that you get if you plot the ages against the depth 

 of the peat. We have a core from the marsh at Barnstable 

 from a depth of 325 inches with an age of about 5, 500 years. 

 It indicates a rise in sea level at a mean rate of 6 inches per 

 century. A second core from a depth of 200 inches from the 

 same boring has an age of about 1,900 years; giving a rise in 

 sea level at a mean rate of more than 10 inches per century. 

 One might conclude that this marsh had grown upward slowly 

 from 325 to the 200 inch horizon, and then more rapidly to the 

 present level. However, we also have a sample from Center- 

 ville, on the opposite side of Cape Cod, with an age of about 

 2,000 years from a depth of only 70 inches, corresponding to 

 a mean rate of 3. 5 inches per century. 



I think the deeper sample from Barnstable gives reliable in- 

 formation because the peat was from right above the clay 



110 



