Evidence for a rising sea level in the region is provided by: 



(1) The existence of peat at depths up to 28 feet below MHW. 



(2) A cliff cut by the sea in the moraine anchoring the base of the sand 

 spit which descends 19 feet below the high marsh level. 



(3) An island, rising from the marsh, formed by a sand hill submerged 

 to a depth of 15 feet in marsh peat. 



(4) Deposits of fresh water peat and cedar stumps overlain by as much 

 as 6 feet of salt peat. 



(5) Recent tide gauge records (Marmer 1948). 



The marsh appears to have formed first along the southern margin border - 

 ing the high land, where a band of peat more than 20 feet in thickness is found. 

 A similar band extends along the northern margin close to the sand spit. This 

 band decreases in thickness from 19 feet at the base of the sand spit to 7 feet at 

 the eastern terminus of the high marsh. At increasing distances from these 

 marginal bands the thickness of peat decreases and is least bordering the larger 

 creeks. See Figure 10. 



These observations suggest that, after the development of bands of marsh 

 fringing the shore at a lower stage of sea level, the marsh grew outward over 

 the sand as it accumulated in the open water. The existing creeks represent the 

 last areas to remain open. During the same period the sand spit grew eastward, 

 followed by the development of the fringe of marsh along its shore. 



Estimates based on the rate of growth of the sand spit during the last 100 

 years, and on the decreasing depth of the peat along its margin (assuming a rise 

 of sea level of 0. 5 foot per century based on carbon dating) agree in indicating 

 that about 3,000 years was required for the growth of the sand spit and for the 

 development of the high marsh which it encloses. 



The initial stages of development of marsh on recently formed sand spit 

 are found at its eastern extremity, where lenticular patches of S. alter niflora 

 occur. Further westward the coverage becomes continuous, the plants growing 

 on gravel and sand without having produced a turf. Salic or nia , and later S. 

 patens occur at high tide level in this region without contacting the S. alterniflora 

 cover. Still further west the foreshore is covered by a broad band of S^. alterni - 

 flora growing in 18-30 inches of peat. At the high water level narrow bands of 

 Salicornia and S. patens fringe the sand hills. This condition terminates abrupt- 

 ly at a small creek, beyond which typical high marsh of apparently much greater 

 age is found. The surface is flat, contains many pond holes, and terminates sea- 

 ward in an eroded bank. The peat exposed is brown and fibrous to a depth of two 

 feet, below which it is gray due to a higher clay content. See Figure 11. 



The development of new marsh on the intertidal sand flats follows a dif- 

 ferent course. Wherever the elevation of the sand becomes sufficient, small 

 islets of S. alterniflora appear, first as scattered plants, later continuous 

 patches some yards in diameter. The latter catch drifting sand and build up a 

 sheet of sandy turf rising above the surrounding sand flat. As the islands grow, 



38 



