Sediments of Kaw Lake, a Glacier-Dammed Lake in Kansas

As described by Todd (1918, Ks Acad Sci Trans), at the maximum extent of the so-called Kansan glaciation, the continental ice sheet flowed into the northeastern corner of Kansas and dammed the valley of the Kansas River. Upstream from the ice dam Kaw Lake formed as the Kansas River and its tributaries were backed up. Kaw Lake sediments are preserved in a buried-valley fill on the campus of Kansas State University in Manhattan, KS, and we cored them in April, 2008. The goals of our work are to determine the paleoenvironment at the time of deposition and the age the lake sediments.

The total length of the core is 65 ft (18 m), including approximately 15 ft (4.6 m) of loess at the top that overlie 50 ft (15 m) of lake sediments. The lake sediments consist of silty clay, silt, and fine sand, and bedding is disrupted in soft-sediment deformation. In rare cases where undisturbed bedding is preserved, it consists of horizontal lamination and starved-ripple lamination. Below about 27 ft (8 m) the lake sediments are gray; above that depth they are oxidized pale brown.

Analyses include grain size, sand petrography (and provenance), environmental magnetism, carbonate content, organic-matter concentration, pollen, optically stimulated luminescence, and paleomagnetism. Preliminary results suggest that the lake sediments have normal magnetic polarity and are likely younger than 780 ka.