24-8 Controls on Holocene Lake-Fen–Bog Transitions in a Wetland Complex, Western New York

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

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Abstract:

The classic model of bog succession describes a gradual, climate-independent progression from open lake to fen and ultimately bog as sediment and organic matter slowly infill a basin. Recent studies, however, suggest that bog development can be episodic and sensitive to climate variability, with abrupt or reversible fen–bog transitions driven by changes in precipitation or drought. The Mud Pond–Zurich Bog wetland complex in western New York provides an opportunity to evaluate these competing models. Initial coring in 2014 revealed a stratigraphy broadly consistent with gradual basin infilling following drainage of Glacial Lake Iroquois at ~13.3 ka, but a single core cannot distinguish spatially controlled infilling from basin-wide, climate-driven change. This study uses multiple sediment cores collected along a basin-margin to basin-center transect to assess whether sedimentary transitions, including fen–bog transitions, are diachronous or synchronous across the basin. We applied a multi-proxy approach, including visual description, magnetic susceptibility, smear-slide analysis, loss-on-ignition (% organic matter, carbonate, lithogenous material, and biogenic silica), and high-resolution μ-XRF elemental analysis to document lithofacies. Lithofacies vary across the basin, consistent with a classic infill model. The basin-margin core bottoms in gray lacustrine clay overlain by alternating herbaceous and woody peat, whereas basin-interior cores contain lacustrine clay, silty sand, banded carbonate and organic-rich sediment, and both herbaceous and woody peat. Because stratigraphic sequences differ across the basin, we use high-resolution (0.5 mm) μ-XRF data to assess basin-wide shifts in water level through changes in elemental indicators of detrital influx (Ti, K), redox conditions (Mn/Fe), and authigenic carbonate precipitation (Ca/Ti). Synchronous shifts in μ-XRF elemental ratios across contrasting lithofacies provide a means to evaluate whether Holocene hydrologic change reflects basin geometry or regional climate forcing. Preliminary radiocarbon age control suggests that basin geometry likely played a dominant role in early postglacial hydrologic change and lake-to-fen development, whereas later Holocene fen–bog transitions may reflect increasing influence of regional climate variability. In the basin center, water-table fluctuations inferred using Mn/Fe and Ti appear to correspond with variations in the basin-margin core.

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