ARCHAEOLOGY AND SALT MARSH PROBLEMS IN 

 THE TAUNTON RIVER VALLEY, MASSACHUSETTS 



by 



Hugh M. Raup 

 Harvard University Forest 



This paper reports the botanical phases of a collaborative study made by 

 Frederick Johnson and the present author at an archaeological site on Grassy 

 Island. The essential features were published in 1947 , and are only sum- 

 marized here, with some revisions in the calculations of the age of the site. 



Grassy Island is situated in Smith's Cove, a small abayment of the 

 Taunton River estuary in southeastern Massachusetts. It is entirely covered 

 with brackish water marsh, which grows on the surface of the mass of salt 

 marsh peat of which the island is composed. This peat rests in turn upon the 

 shallow, level to very gently rolling, bottom of the cove. The bottom is made 

 up of glacial till and outwash deposits. The tidal range at the Island is approx- 

 imately 2.8 feet, and ordinary high tide bathes the surface. Spring tides somie- 

 times cover it entirely. Mean low tide is approximately at the base of the peat. 

 The main channel of the Taunton River is close to the western shore of the cove. 



Interest in Grassy Island stems from the presence at the base of the peat 

 of an archaeological site containing an abundance of stone tools and the remains 

 of hearths. A basic purpose of our studies of the island peat and its present 

 vegetation has been to date, if possible, the time at which the site became un- 

 inhabitable to Indians due to the advance of the tide which now covers it. 



Certain assumptions are made at the outset because they appear to be re- 

 liable and well documented. One is that there has been a continuous rise of sea 

 level with respect to the land for some thousands of years, and that this rise 

 continues. Second, it is assumed that the rate of rise has been relatively slow 

 and steady, being at no time in the last 2000 years or so greater or less than 

 the rate of accumulation of the peat, which is made up primarily of high-tide 

 grasses. Third, the identification of the peat as being composed primarily of 

 these high-tide grasses (chiefly Spartina patens at Grassy Island) rather than of 

 mid-tide grasses (Spartina alterniflora) is held to be reliable because of readily 

 observed differences in the preserved rhizomes of these grasses. Many borings 

 of salt marsh peat in southeastern New England have shown that the accumula- 

 tions are composed primarily of the high-tide species, and there appears to be 

 no other explanation for this except one which involves a steadily advancing 

 strand line. Furthermore, many of these marshes are underlain by some fresh 

 water peat, indicating that at the beginning they were invaded by advancing sea 

 water. 



1) Johnson, Frederick and Hugh M. Raup. Grassy Island: Archaeological and 

 Botanical Investigations of an Indian Site in the Taunton River, Massachusetts. 

 Papers of the R.S. Peabody Foundation for Archaeology, Vol. 1, No. 2, 68pp. (1947). 



116 



