USING LOSS-ON-IGNITION TO DELINEATE ZONES OF HIGH ORGANIC CONTENT IN LAKE SEDIMENT FROM ICE-PROXIMAL LAKES, SOUTHWESTERN WISCONSIN
Sediment from an initial location of interest, Marsh Valley in northwest Dane County, WI, was sampled at fixed 8-cm intervals and processed for charcoal and pollen. Initial analyses indicated low counts for both charcoal and pollen. We recognized that the lake sediment consists of interbedded zones of silty sandy layers, unfavorable for proxy preservation, and more productive organic-rich layers, which required a refined processing plan. A more intensive 1-cm sampling resolution was used to constrain the organic-rich zones along the core that would result in higher pollen and charcoal counts. Subsequent pollen processing resulted in a significant increase in pollen grain counts.
The methods applied to Marsh Valley were extended to 6 other locations along the lower Wisconsin River valley between the glacial margin (to the east) and the confluence with the Mississippi River (to the west) to further refine focus areas for continuing study. Results from pollen counts and LOI analyses show a direct relationship between organic material and optimal proxy preservation. Preliminary LOI analyses provide a general indication of the amount of organic material throughout the core and determine which zones are more suitable for pollen processing.