C.B. Griggs
N.G. Miller
R.E. Nelson
T.K. Weddle
T.M. Kilian
W.B. Thompson
2011
<p><span>Excavations in the late-glacial Presumpscot Formation at Portland, Maine, uncovered tree remains and other terrestrial organics associated with marine invertebrate shells in a landslide deposit. Buds of </span><span class="italic">Populus balsamifera</span><span> (balsam poplar) occurred with twigs of </span><span class="italic">Picea glauca</span><span> (white spruce) in the Presumpscot clay. Tree rings in </span><span class="italic">Picea</span><span> logs indicate that the trees all died during winter dormancy in the same year. Ring widths show patterns of variation indicating responses to environmental changes. Fossil mosses and insects represent a variety of species and wet to dry microsites. The late-glacial environment at the site was similar to that of today's Maine coast. Radiocarbon ages of 14 tree samples are 11,907 ± 31 to 11,650 ± 50 </span><span class="sup">14</span><span>C yr BP. Wiggle matching of dated tree-ring segments to radiocarbon calibration data sets dates the landslide occurrence at </span><span class="italic">ca.</span><span> 13,520 + 95/−20 cal yr BP. Ages of shells juxtaposed with the logs are 12,850 ± 65 </span><span class="sup">14</span><span>C yr BP (</span><span class="italic">Mytilus edulis</span><span>) and 12,800 ± 55 </span><span class="sup">14</span><span>C yr BP (</span><span class="italic">Balanus</span><span> sp.), indicating a marine reservoir age of about 1000 yr. Using this value to correct previously published radiocarbon ages reduces the discrepancy between the Maine deglaciation chronology and the varve-based chronology elsewhere in New England.</span></p>
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10.1016/j.yqres.2011.02.002
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Cambridge University Press
Associated terrestrial and marine fossils in the late-glacial Presumpscot Formation, southern Maine, USA, and the marine reservoir effect on radiocarbon ages
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