CHARACTERIZATION OF HIERARCHICAL HETEROGENEITY USING INDICATOR GEOSTATISTICS IN THE CONFLUENCE AREA OF THE MAHOMET AND MACKINAW BURIED-VALLEY AQUIFER SYSTEMS

In the Mahomet and Mackinaw aquifer systems in central Illinois, heterogeneity was characterized at two scales for the purpose of developing ground water models. At the larger scale are regionally correlatable stratigraphic units. These units are composed of heterogeneous mixtures of mud and diamicton facies (m) and sand and gravel facies (s). At the smaller scale the indicator geostatistics formalism was used to both characterize and model the proportions, geometry, and distribution of facies within each unit and to define the boundaries of the units themselves. We defined the units by delineating assemblages of facies m and s with relatively distinct and stationary statistical attributes. In results thus far, vertical transition probability models were developed for each facies assemblage, which represent the proportions, geometry, and pattern of the facies. Lateral correlation is currently being evaluated. Future work will use a conditional sequential indicator simulation algorithm to produce three-dimensional realizations of the facies assemblages. The interconnectedness of facies s throughout the complex of sediments will then be studied because this represents preferential pathways of flow.