IS BOLLING WARMING RECORDED BY THE SOUTHEASTERN MARGIN OF THE LAURENTIDE ICE SHEET?

The effect of prominent climate events, such as the Bölling warming (13,000 14C yr B.P.), on the dynamics of the Laurentide Ice Sheet (LIS) remains unknown, and yet had important implications 1) for understanding the impact of climate changes on the largest temperate ice sheet, and 2) for assessing the possible contributions the LIS could have made to global meltwater pulse 1A and sea-level changes in general.

Keeping in mind the current chronological limitations, the detailed emerged glacial and glacial-marine record in coastal Maine is interpreted at present as resulting from a slow, fluctuating recession of a low-profile ice sheet, followed by steepening of the profile and readvance, which terminated with deposition of the very prominent Pineo Ridge Moraine Complex (PRC), a record that now can probably be extended across Maine and into New Hampshire. Emplacement of the PRC was followed by “abrupt” melt down of the ice to the north, accompanied by lack of clear evidence of internally dynamic ice. Based upon the few relevant 14C dates, the rate of ice-margin recession south of the PRC was approximately 10m/yr, where as that to the north increased from 30-40 to 150 m/yr.

Ongoing chronological and ecological research indicates that the Maine deglacial stratigraphy, developed for the time between approximately 14,000 and 12,500 14C yr B.P., essentially parallels the temperature reconstructions for the Oldest Dryas and the subsequent interhemispheric abrupt onset of Bölling warming. This, in turn, indicates that the deglaciation was driven primarily by atmospheric rather then marine events.