COULOMETRIC ANALYSIS OF A SEDIMENT CORE FROM SWIFTCURRENT LAKE, GLACIER NATIONAL PARK, MONTANA

Sediment records of organic and inorganic carbon in lakes can serve as a proxy for recent anthropogenic and Holocene environmental change. Two >5-m lake cores were collected using a push piston corer in Swiftcurrent Lake, Glacier National Park, in July 2005. Swiftcurrent Lake is the most accessible, shallowest, and farthest downstream lake of a series of four glacially carved lakes that receive meltwater from Grinnell Glacier. In this study, we present coulometry measurements at 1-cm intervals of total carbon (TC), total inorganic carbon (TIC) and total organic carbon (TOC) of the core collected closest to the Grinnell Stream inlet. Organic carbon content reflects bioproductivity in the lake and surrounding area while inorganic carbon indicates presence of carbonate minerals. Preliminary samples contain 3% TC, which likely represents a mix of carbonate sediment and organic material. Age control for the core is constrained by C-14 ages of two charcoal layers and a Mt. Mazama ash deposit (6730 ka). Average early Holocene sedimentation is 0.46 mm/yr, middle Holocene is 0.58 mm/yr, and late Holocene is 0.77 mm/year. Given a total core length of 650 cm, the core represents approximately 10,000 years. Anthropogenic activity may be detectable in the first five centimeters of the core after the 1915 completion of a lakeside hotel Swiftcurrent Lake. We expect to find evidence of Holocene climatic fluctuations and anthropogenic activity in the carbon content data.