LATEST PLEISTOCENE MARINE MOLLUSCS OF CENTRAL MAINE: EVIDENCE FOR PALEOSALINITY AND PALEOBATHYMETRY IN THE WANING PHASES OF THE PRESUMPSCOT FORMATION AND SUBSEQUENT MARINE EMERGENCE

In central and coastal Maine, the immediately postglacial record is predominantly one of marine submergence and subsequent re-emergence of the land. The timing of this re-emergence and character of the initial landscape are of particular importance and interest. Three samples were taken from each of four diffusely fossiliferous pockets of shelly marine silts in an abandoned gravel pit in Norridgewock, Maine, at approximately 44^o43.1'N, 69^o48.9'W; samples were all collected from within the upper 6.5 m of the massive marine silts of the Presumpscot Formation. Separate small samples were taken for ostracode and foraminiferal analyses, and large bulk samples were collected for molluscan faunal study and radiocarbon age determination. Though results from ¹⁴C samples are pending, past experience has been that comparable samples in this region yield ages of 12,300-12,500 ¹⁴C years b.p. This presents initial results of the study of the molluscs found in the unit. All samples were dominated by broken fragments of Mytilus edulis and Balanus sp. Portlandia artica and Hiatella arctica were also common, with (in order of decreasing abundance) Macoma balthica, Mya arenaria, Buccinum sp., and Serripes groenlandicus completing the faunas. Modern habitats for these species suggest a polyhaline (18-34 ppt), moderately shallow or intertidal habitat ranging from muddy shallows (≤ 5 m) to moderately deep water (20 m ?); water temperatures could have been as low as 0^oC, and the diversity of the fauna suggests moderate turbidity. Taken together, the observed macrofauna suggest that the depositional environment was affected by both intertidal interactions as well as a significant amount of outwash from rapidly melting proximal ice.