LANDSCAPE CHANGES AND MASS WASTING EVENTS AS RECORDED IN THE SEDIMENTS OF SLUICE POND, MASSACHUSETTS

Long-term environmental trends such as land use dynamics, climatic changes, as well as instantaneous events such as mass movements can leave an imprint in the sedimentary record of lakes. Here, we investigate two short sediment cores of Sluice Pond in Lynn, Massachusetts using a multi-proxy approach. The sediment’s dry density, grain size, and elemental composition were analyzed. Organic particles were chemically removed to determine the grain size distribution of the mineral component of the sediment using laser diffraction granulometry. X-Ray Fluorescence (XRF) was used to measure elemental compositions and determine elements of interest (Ti, K, Mg, Fe, Ba, Ge, Al). An existing Bayesian age model based on industrial contaminants, pollen stratigraphy, and radioisotopes was refined using newly obtained radiocarbon dates. This allows for good age control for the upper 80 cm of the cores or the last 1,200 years. Sluice Pond sediment is composed of dark-brown organic-rich mud. The lower record deposited before ~1750 AD is coarser with an abundance of medium to coarse silt (30 - 40 microns). Above 29 cm core depth and deposited after ~1750 AD, grain size distributions decrease and show a dominance in the fine to medium silt range (5 -30 microns), likely a result of soil erosion caused by deforestation. At 73 cm, 53 cm, 48 cm, and 30 cm core depth, particle sizes increase, indicating a sudden influx of nearshore sediment possibly from mass wasting. Elemental compositions of the identified elements show a sharp shift towards higher values at 53 cm and 30 cm core depth, corresponding to ~1400 AD and ~1750 AD respectively, matching trends in grain size and marking a possible influx of feldspars and clay minerals and a long-term alteration in the lake’s environment. Future work will involve increasing the resolution of our proxy data from Sluice Pond and comparing it to the sediment record of nearby Walden Pond, to identify large-scale trends and regional events.