Lacustrine records of post-glacial environmental change from the Nulhegan Basin, Vermont, USA



The sedimentary records of Nulhegan Pond and Beecher Pond in the Nulhegan Basin of north-eastern Vermont were analyzed to yield a history of environmental change since the latest Pleistocene. Shoreline landforms indicate that part of the Nulhegan Basin was inundated by Glacial Lake Nulhegan (GLN), which was impounded behind a dam of glacial sediment. Outwash derived from stagnant ice forms the bottom 176 cm of the Nulhegan Pond core. Fine-grained inorganic sediment deposited between 13.4 and 12.2k cal a BP is interpreted as a deep-water facies representing GLN, while coarser sediment from 12.2 to 11.8k cal a BP records draining of the glacial lake. Rapid, simultaneous increases in organic matter and biogenic silica signal the onset of productivity following the Younger Dryas. Beecher Pond formed c. 11.3k cal a BP through surface collapse over a buried ice block; buried stagnant ice may have persisted in the vicinity of the pond into the early Holocene. From 8.9 to 5.5k cal a BP, sediment in both lakes became coarser and richer in aquatic organic matter, suggesting a low-water phase in which previously deposited lacustrine sediments were reworked and the littoral zone shifted basinward. Low water levels at this time are consistent with other records from Maine and southern Quebec, but contrary to records from ∼325 km to the south. Copyright © 2012 John Wiley & Sons, Ltd.