John J. Quinn Environmental Science Division, Argonne National Laboratory
Room 101, Natural Resources Building 615 E. Peabody Drive, Champaign
Illinois State Geological Survey
Geostatistical methods provide a means for exploring that correlation structure, allowing comparisons of results from different geomorphological settings and approaches. In this study, indicator geostatistics and transition probability geostatistics are applied to nearly 300 km of drilling data derived from over 11,000 private well drilling logs and over 200 high-quality well logs from monitoring well installation. Analyses are focused on a 12,000-km2 region in central Minnesota in a setting dominated by the late-Wisconsinan Rainy, Superior, and Wadena lobes.
Results for the numerous geomorphological settings indicate overlapping geostatistical ranges, sills, and vertical lens thicknesses. A lack of stationarity was observed, consistent with a fundamental complexity of glacial depositional and erosional processes. Correlation generally varied as much between geographically distinct zones of like geomorphology as it did between zones of different geomorphology. High-resolution data associated with monitoring well installation typically deviated from the private well data; this is attributed to site-specific geology and detailed logging of thin units. Overall results underscore the difficulty in correlative assumptions in glaciated regions.