24-3 Late-Glacial and Holocene Threshold Behavior in a Western New York Kettle Pond

Session: Lake Sedimentary Records of Past Climate and Environment (Posters)

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Abstract:

Because small kettle ponds with limited watersheds respond rapidly to environmental forcing, they are well suited to capturing short-lived climate events and threshold responses- abrupt, nonlinear shifts in lake state- that may be muted or absent in larger lakes. We investigated the late-glacial and Holocene watershed and lake history of Round Pond in western New York (surface area: 0.024 km²; maximum depth: 9.14 m) to identify the processes governing basin evolution. A 6.5-m-long sediment core collected from the pond margin in 2023 preserves a continuous archive spanning the late deglaciation to the present. The core preserves five lithofacies reflecting distinct depositional environments: proglacial clay, laminated silty sand with mollusks, sapropel, bedded to laminated carbonate-rich mud with abundant mollusks and charophytes, and peat. We used a multi-proxy approach including smear-slide analysis, loss-on-ignition (LOI; organic matter, carbonates, and incombustible material), magnetic susceptibility (MS), and elemental composition from micro-XRF core scanning.  

Low organic matter (<10%), absence of diatoms and mollusks, and dominance of clastic minerals (~60–80%) in the basal clay indicate cold, deepwater conditions associated with Glacial Lake Warren, with high clastic inputs reflected by elevated MS and Ti, K, and Zr values. Drainage of Glacial Lake Warren represents a hydrologic threshold marked by an abrupt transition to the laminated silty sand unit. Declining MS and elemental values in the sand unit indicate progressively reduced clastic input typical of a newly deglaciated landscape. Subrounded granules and small bivalves suggest nearshore deposition within a newly formed lake by ~12 ka, with total Holocene sediment thickness indicating basin water depths of at least ~7 m. A subsequent reduction in clastic delivery produced the sapropel unit dominated by algal material (~75% organic matter) including diatoms and no carbonate, reflecting a stable profundal lake state. A rapid transition to banded carbonate mud marks a geochemical and ecological threshold, with increased carbonate (~40%) and the appearance of charophytes, bivalves, and gastropods, indicative of shallow (0.5- 7 m), alkaline, productive conditions. Carbonate accumulation along the western basin margin reflects macrophyte colonization and marginal infilling, leading to basin-wide stabilization driven primarily by autogenic succession, potentially initiated by climate-driven water-level change. Additional radiocarbon ages will further constrain the timing of these thresholds.

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