Gary drift border passes into the sea at Boston and probably lies in the Gulf of Maine. 

 Pollen profiles from Aroostook County, in northern Maine, seem to indicate that the 

 Gary Ice Sheet was the last to occupy Maine and that the Late Wisconsin Mankato 

 Ice Sheet probably did not extend farther south than the northern part of the state 

 (Deevey, 1951; Flint and Deevey, 1951). Its proximity is reflected by a return of 

 a tundra type climate to northern Maine. 



Following, or possibly concurrent with, the retreat of the last ice sheet from 

 southern Maine, the sea advanced over the isostatically depressed coastal area. 

 Leavitt and Perkins (1935) believe that the sea reached a maximum of 300 feet above 

 present sea level at Searsport . Other evidence by Deevey (1951) and by Bloom (1959), 

 working in southwestern Maine, indicates that this figure is of the right order of mag- 

 nitude. Radiocarbon dating of marine shells at Waterville, Maine, gave a date of 

 11,800 ±240 years B.P. for the time of maximum submergence (Bloom, 1959, p. 80). 

 This date is probably applicable to the Penobscot Bay region, and it closely corre- 

 sponds to the Two Greeks Interval; the Gary-Mankato Interval . 



Isostatic recovery of the depressed land areas following deglaciation resulted in 

 a retreat of the sea. Bloom (1959, p. 85), interpreting a pollen profile (Deevey, 

 1951) from Muddy Pond in Kennebec Gounty, believes that emergence was in prog- 

 ress 7,000 to 8,000 years ago. Emergence may have continued until sea level was at 

 least 35 feet below present level (Bloom, 1960). Bloom (1960) states that sea level in 

 Maine has been at -10 feet for the past 6,000 years. Flint and Deevey (1951) cite 

 a former emergence of 15 to 30 feet at the Boylston Street fishwier site in Boston. 

 Radiocarbon dates place this emergence at about 5, 700 years B.P. and submergence 

 about 3, 850 years ago. The dates and extent of postglacial emergence in coastal 

 Maine are still not known precisely. The coast of Maine is currently undergoing 

 gradual submergence (Marmer, 1949). 



The glacial and postglacial sediments in the Penobscot Bay area have been de- 

 scribed by Bastin (1908) and Smith, Bastin, and Brown (1907). The till in the region 

 is thin and irregular, reaching a maximum of 40 to 50 feet In valleys and depressions. 

 Outwash sands and gravels are rare In the southern part of the area, but they become 

 more abundant to the north. These deposits lie on fresh bedrock. 



The transgression of the sea resulted in the deposition of the marine clays so prev- 

 alent in southern Maine. The clays are described by Bastin (1908) to be yellow-ish 

 gray to blue gray, very fine grained, and free of pebbles and sand. The clays are com- 

 monly 15 to 35 feet thick, but 50- to 75-foot thicknesses are known from wells. The 

 clays are found in river valleys as far as Bangor, 25 miles north of Searsport. Accord- 

 ing to Bastin (1908), the clays represent "old clam flats." This view is supported by 

 Goldthwait (1949) inasmuch as the clays are found only m the lower portions of valleys 

 and have a well defined topographic upper limit in any given area. These clays are 



