Distinguishing Pleistocene Proglacial Lakes in Western New York Through Mineralogy and XRF

Proglacial lake extent related to the deglaciation of the Laurentide Ice Sheet (LIS) is based on field relationships and strandline elevation. However, there are gaps in well-defined shorelines, especially in western New York. Pink and gray clays in the Great Lakes and Finger Lakes regions of western New York are characteristic of proglacial lakes making Mendon Ponds Park (MP), Zurich Bog (ZB) and Seneca Lake (SL) good candidates for constraining sediment source regions and proglacial lake extent. Cores from these sites were collected and analyzed using loss-on-ignition, magnetic susceptibility, and X-ray florescence (XRF). Two XRF proxies were used to determine if sediment derived from local limestone (Ca+Sr/Ti) or sandstone (Si+Fe/Ca+Sr) units.

The proglacial interval of the MP core (635-707 cm) contains two units, pink (680-707 cm) and gray (635-680 cm) clays. Minerals in both units include carbonates and clays, with larger grains of quartz, iron oxides, and mafics, including epidote. Proglacial SL sediment (290-330 cm) has a similar composition to MP pink clay, including coarser silt, very fine sand, and mafic grains. Proglacial ZB sediment (1180-1224 cm) is similar to MP gray clay, including algal matter and fine silt. Similarities between MP and SL pink clay and MP and ZB gray clay are also reflected in XRF data. Several source regions for the pink and gray clays were identified. Epidote, found in all core sediments, indicates a source region from the Adirondack Mountains, where sediment was likely transported by the Ontario-Erie Ice Stream. Higher Si+Fe/Ca+Sr values in the pink clay of ZB and MP reflect sources from hematite-rich Silurian sandstones and glacial till. Higher Ca+Sr/Ti in the gray clay of SL and MP reflect a Devonian limestone source. Shifts in local source regions indicate a retreat followed by a readvance of the LIS. Basal post-glacial sediments of MP are dated to 13.120 cal ka BP (Clark et al., 1996), making Proglacial Lakes Warren (15.0 ka BP) and Iroquois (13.0 ka BP) (Lewis et al. 2021) likely candidates for the deposition of pink and gray clays, respectively. XRF ratios coupled with regional bedrock chemistry and mineralogy provide an additional method of distinguishing proglacial lakes.