since the form and topography of this horizon does indicate a lower stand of the 

 sea . This horizon is relatively flat in the northern sector of the bay and appears 

 to be graded to some lower stand of the sea whereas to the south in deeper water this 

 appearance and this form are lost.lt is postulated that the subbottom surface in the 

 northern part of the bay owes its development to a postglacial retreat of the sea 

 and sediment reworking and deposition in mudflat, deltaic, or sub-deltaic environ- 

 ments . 



The stratified deposits noted on run I, between marks A and B, and at core 

 locations 138, 139, and 210 are all found immediately below the subbottom horizon 

 and appear to be channel deposits of the Penobscot River. The alignment of these 

 stations is suggestive of this origin. (Similar deposits were also noted at station 

 152.) To the west of this area but still in the northern sector, the depth of the 

 subbottom horizon increases abruptly and is cut by numerous channels. This area 

 was probably in the direction of the major drainage from the Penobscot River. The 

 channeling of the subbottom layer in the vicinity of stations 202 to 208 is probably 

 an erosional feature developed in fairly shallow water. 



The topography on the late-glacial clays may be an original depositional fea- 

 ture, but the coarse material found above, marking the subbottom horizon, requires 

 a lower level of the sea at the time of deposition of the coarser sediments. The ex- 

 tent of the drop In sea level is not known for this area and cannot be precisely 

 determined from the evidence on hand, but it is probably on the order of 50 to 60 

 feet. The date when this event took place, however, can be defined more close- 

 ly. The wood obtained In core 211 at a depth of 94 inches below the bottom was 

 dated by the radiocarbon laboratory of the U.S. Geological Survey (sample number 

 W 1306) . The sample dated 7, 390 ± 500 years B .P . The Sonoprobe record at this 

 location shows the subbottom horizon at a depth of 7 1/2 to 8 feet below the bottom . 

 The sample of wood was obtained slightly above or at the depth of this horizon. 



In the earlier discussion of the glacial and postglacial history of Maine, the 

 following was stated: the maximum submergence was about 11,800 years B.P., emer- 

 gence was in progress 7,000 to 8,000 years ago in southwestern Maine, with the 

 maximum emergence, on the order of only about 35 feet, occurring prior to 6,000 

 years ago. In Boston emergence was 15 to 30 feet and occured 5,700 years B.P. The 

 date for Penobscot Bay places the emergence farther back in time and was of a great- 

 er extent than for any of the places mentioned above. Redfield and Rubin, (1962) 

 have plotted a number of peat and wood sample dates for southern New England, New 

 Hampshire, Maine, and Nova Scotia. Although the majority of the dates are for less 

 than 4,000 years, the few older samples and the trends of the southern New England 

 and Nova Scotia samples Indicate that the Penobscot Bay date Is compatible with a 

 lower sea level of 50 to 60 feet . It should be noted, however, that the Maine and 

 New Hampsire dates do not provide good agreement with the Penobscot Bay date. 



48 



