THE PRE-EUROPEAN SEDIMENTARY RECORD OF SLUICE POND, MASSACHUSETTS: A DETAILED ARCHIVE OF LONG-TERM TRENDS AND INSTANTANEOUS SEDIMENTATION EVENTS

The sedimentary record of lakes can indicate both long-term environmental trends in a region, such as land use dynamics or changes in climate, and instantaneous events like mass movements. A sediment core, SP13-KC1, was collected from Sluice Pond in Lynn, Massachusetts in 2013. Using a multi-proxy approach on the core, we focused on the deposits below the well-defined Ambrosia horizon at 1629 CE to reconstruct pre-European sedimentation processes in the lake. We measured dry density, grain sizes, and elemental compositions of the sediment. Organic particles were chemically digested in order to obtain the grain size distribution of the mineral component of the sediment using laser diffraction granulometry. We measured the elemental composition using X-Ray Fluorescence pED-XRF (Spectro XEPOS-He). A previously developed age model allows for robust age control for the last 1200 years, and is based on industrial contaminants, radiocarbon dates, pollen stratigraphy, and radioisotopes ²¹⁰Pb and ¹³⁷Cs. Sluice Pond sediment is primarily composed of dark-brown organic-rich mud. Sediments deposited since the mid-18th century are mostly fine to medium silt washed into the lake following deforestation of the area. Sediments deposited between 1450 and 1750 CE are predominantly coarse silt, whereas sediment deposited before 1450 CE is consistently finer and in the medium silt range. We are refining the grain size record to better understand environmental changes before European colonization and identify event layers related to prehistoric floods, earthquakes, or fires. Elements of interest that indicate detrital input include Ti, K, Mg, Fe, Ba, Ga, and Al, which tend to occur in elevated concentrations higher in the core, corresponding with the grain size pattern. Principal Component Analysis (PCA) will be used to identify characteristic elemental fingerprints linked to gradual and sudden sedimentation changes. Future work will include comparison to other lakes in the area, such as Walden Pond, to identify regional environmental trends and potential triggers for instantaneous sedimentation events.