HOLOCENE STRATIGRAPHY AND CLIMATE HISTORY OF SLUICE POND, MA

Recent work, including pollen and lake level studies in New England, demonstrates the dynamic nature of climate variability during the Holocene Epoch. Here, we investigate the seismic- and litho-stratigraphy of Sluice Pond, MA and reconstruct local climatic conditions. We collected sub-bottom profile data and two dated sediment cores (deep basin and margin locations) between 2007-10. Sediment proxy data include pollen and thecamoebian abundances, organic matter deposition (LOI), density, magnetic susceptibility, δ¹³C, δ¹⁵N, and C/N ratios.

The lower portion of the basin core reveals a time of cold/dry climate from ca. 11,500 - 8,000 cal BP. Evidence includes Picea and Pinus pollen zones, geophysical reflectors that pinch out at depths <18m, generally low organic matter preservation, and a lack of sedimentation in the margin core. An increase in regional temperature/moisture is apparent in sediments younger than 8,000 cal BP. Pollen data indicate the establishment of a mixed forest ecosystem. Organic matter deposition reaches a maximum in the basin core, and the initiation of gyttja deposition in the margin sediment core at 7,800 cal BP confirms a lake level increase.

A warm/dry climate is suggested from ca. 5,000 – 3,500 cal BP. This interval has been identified as the Tsuga minimum zone. During this time interval, the marginal core contains an abundance of macrophyte remains, suggesting a decrease in lake level to account for the macrophyte’s affinity for the photic zone. The warm/dry period had a delayed trigger on productivity as organic matter deposition first decreased and then increased along with an increase in thecamoebian abundance at ca. 4,000 cal BP. Younger sediments suggest unstressed, organic-rich conditions until the most recent sediments. The upper-most sediments record anthropogenic disturbance with increases in non-arboreal and Betula pollen, the stress-tolerant thecamoebian Difflugia protaeiformis, and a large increase in δ¹⁵N. Additionally, increases in magnetic susceptibility, trace metals, and dry bulk density, along with a relative decrease in organic matter, argue for land-use change. The climate variability interpreted from the sediments of Sluice Pond is consistent with other studies from New England, suggesting regional climatic forcings.