Comparative Heavy Mineral Analysis of Wisconsin and Illinoisan Glacial Till from the Locations of Walden West and East Fork State Park: A Test for Provenance and Sediment Recycling

This study used heavy mineral assemblages extracted from glacial till to evaluate if deposits from the Wisconsin (25,000-13,500 ybp) and Illinoisan (300,000-125,000 ybp) ice sheets were related by either provenance (source) or... [ view full abstract ]

This study used heavy mineral assemblages extracted from glacial till to evaluate if deposits from the Wisconsin (25,000-13,500 ybp) and Illinoisan (300,000-125,000 ybp) ice sheets were related by either provenance (source) or recycling of older deposits. Wisconsin till was collected from Walden West in Tipton, Michigan and Illinoisan till was collected from East Fork State Park in Bethel, Ohio. This study hypothesized that the moraines were related and the heavy mineral samples from Wisconsin and Illinoisan till are compositionally indistinguishable. To test the hypothesis, two samples of glacial till were collected and the heavy mineral content was analyzed using a petrographic microscope to count the number of grains of each mineral (a point count analysis). A chi-square goodness-of-fit test was applied to the point-count data, where the Walden West sample was considered the observed value and the East Fork sample, after normalization, was considered the expected value. Results of the chi-square test show the sample populations are statistically distinct at the 95% confidence level and the study hypothesis is rejected. This study concludes the composition of till deposited during the past two glacial periods are distinct from one another, suggesting the till may have been sourced from different areas and that Wisconsin till is not exclusively composed of reworked Illinoisan till.