My Projects

Glaciers

Lakes

Rivers

Sediment cores from Swiftcurrent Lake and Lake Josephine

As part of my interest in constraining rates of subglacial erosion below Grinnell Glacier, we collected lake cores in two glacial lakes downvalley (and downstream) of the glacier. Sediment deposited in Swiftcurrent, Josephine, Lower Grinnell, and Upper Grinnell Lakes captures environmental change over the Quaternary, and can be used to deduce glacial erosion rates since the Last Glacial Maximum (~18 ka). We collected four cores from Swiftcurrent Lake (two exceeded 5 m in length) and one core ~5 m long from Lake Josephine. Ash from the Mt. Mazama eruption was found near the base of one core; the well-known age of this eruption (7500 BP) combined with radiocarbon dating of charcoal found in the sediment demonstrates our longest record spans ~10,000 years. We are continuing to analyze the sediment cores both at Macalester and at the Limnological Research Center at the University of Minnesota. Analyses include: magnetic susceptibility, grain size, xray diffraction, total organic and inorganic carbon (coulometry), charcoal dating and pollen/macrofossil analysis. These data can provide a high-resolution record of climate change in the vicinity of Grinnell Glacier over the last 10,000 years, and may illuminate the erosion history of the glacier itself. The lake coring project is a collaborative effort between myself, Catherine Riihimaki (Bryn Mawr College), and the LRC (University of Minnesota).