| Summary: | U-Pb isotopic ages were determined for zircons extracted from granitic and related rocks in the Tiskilwa till to determine their origin. Crystalline cobbles (n = 750) were collected at localities from each of the four of the sub-lobes of the terminal Wisconsin moraines. Two sites were chosen from the Decatur, Peoria, and Princeton sub-lobes with one sample taken from the Harvard sub-lobe. Each sample was then individually processed, the zircons handpicked (n = 301), and geochronology conducted using LA-MC-ICPMS at the University of Arizona Laserchron Center. A Kolmogorov-Smirnov (K-S) statistical analysis show that all samples have identical zircon age spectra with the populations being dominated by Archean age (>2.5 Ga) grains and peak age being 2.7 Ga. The dominance of Archean grains indicate a source located in the Superior Province, with the Hudson Bay Terrane (3.36–2.69 Ga) being the most likely source area for the granite clasts. In successfully utilizing granite clasts to determine provenance, this study could provide further insight into glacial transport systems.
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