A LATE-GLACIAL RECORD OF ENVIRONMENTAL CHANGE FROM PECKS POND WETLAND, VERMONT

Understanding climate variability during the last deglaciation contributes to our understanding of the feedbacks associated with a warming planet. In central Vermont and other parts of northern New England, paleoenvironmental records from lake and glacial sediments point to an unstable late-glacial climate. This study examines the fingerprint of a lake environment preserved in a sediment core from the Pecks Pond wetland in Barre, VT that extends from 8,000 to >14,500 yr BP. Loss-on-Ignition (LOI), grain-size, and macrofossil analyses indicate a shallow carbonate-rich lake occupied the basin for much of this time period. At the base of the core, low LOI values (5% CaCO₃, 1% organic carbon), high percentages of sand-sized grains (20%), and limited macrofossils indicate high-erosion rates and low-productivity. At ca. 14,500 yr BP CaCO₃ increases to 20%, sand-sized grains decrease to 10% and calcite encrustations and oospores of the macroalgae, Chara sp. increase suggesting a warmer and more productive lake which continues until 13,750 yr BP with the exception of one brief interruption at 14,100 yr BP where there is a reversal in these trends and an increase in the cold-water ostracode, Candona Candida. Between 13,750 and 13,600 yr BP there is a more significant decline in CaCO₃, increased sand-sized grains and a peak in C. candida all of which suggest a colder lake environment. From 13,600 to 12, 750 yr BP CaCO₃ and organic carbon increase to ca. 35 and 5%, while sand-sized grains and concentrations of C. Candida both decline. This data, in addition to the return of Chara macrofossils and a peak in the ostracode, Cypridopsis vidua, suggests that the lake became warmer and more productive during this time. At 12,750 yr BP a drastic and short-lived change in core stratigraphy from lake sediment to peat is matched by changes in LOI values, grain-size, and macrofossils and points to the development of a wetland. Shallow lake conditions return within 100 years and CaCO₃ remain at ca. 35% until 11,250 yr BP which marks a transition to higher (45%) and more stable CaCO₃ percentages. This record shows abundant paleoenvironmental variability that with further radiocarbon dating and macrofossil analysis will provide a much-needed record of climatic variability in northern New England during the late-glacial period.