RECONSTRUCTING PALEOFLOOD FREQUENCY USING HOLOCENE SEDIMENT RECORDS FROM SENECA LAKE, NEW YORK

Existing studies of paleofloods in inland lakes in the northeastern United States rely on methods such as loss-on-ignition, magnetic susceptibility, and grain size; each of which requires manual sub-sampling on a coarse scale (> 1 cm thickness). Flood events, however, may produce thinner layers. These events can be identified using continuous, non-destructive X-ray fluorescence (µ-XRF) scanning along the core at an even higher resolution. This is the first study to use µ-XRF core scanning at a sub-mm resolution to distinguish background sedimentation from flood deposits in Seneca Lake, NY.

Multiple piston cores were collected from the profundal zone of the lake along a North-South transect. Magnetic susceptibility (MS) was measured on unsplit cores using a loop meter. Archived halves of split cores were analyzed using an ITRAX (COX Analytical Systems) µ-XRF core scanner to determine downcore elemental profiles. Log-centered correlation revealed two clusters of data that reflect the dominant sediment types in the lake: autochthonous sediment (Ca, Sr) and terrigenous sediment (Fe, K, Rb, Zr, Ti), consistent with the two laminae types identified during visual logging. Effective proxies for detrital sediment influx included MS, Ti, Zr/Rb (for coarse-grained sediment), and Fe/K (for fine-grained sediment). MS and Ti alone could not be used to pinpoint flood events, as these proxies show long-term changes in upcore concentrations. Spikes in Zr/Rb reveal coarse-grained sediment influx events at ~14-11 ka, ~6 ka, ~3.8-3.5 ka, ~2 ka, and 0 ka. These events may be regional based on the timing of Holocene floods in Fish Creek near Sylvan Beach, NY.