3-D GEOSTATISTICAL CHARACTERIZATION OF FLUVIAL-DELTAIC SEDIMENTARY GEOLOGY IN THE CENTRAL OKLAHOMA AQUIFER

The Garber Sandstone, which is an upper unit of the Central Oklahoma Aquifer, is characterized by a complex network of sands interbedded with shales and mudstones typical of fluvial-deltaic sedimentary structures. Wells associated with an active site remediation program at Tinker Air Force Base in Oklahoma City have produced an extensive dataset of borehole geophysical data, groundwater elevations, and analytical chemistry data useful for evaluating groundwater flow regimes in the Garber Sandstone. 3-D geostatistical modeling, including the use of transition probabilities, provides a toolset for evaluating the lithology of individual hydrostratigraphic units and the lateral continuity of key aquitards. 3-D realizations of the lithology based on geostatistical analysis supplement an existing deterministic 3-D geological model developed from geologists' interpretations. The realizations, when coupled with direct observations from a dense network of monitoring wells, highlight regions in the 3-D hydrostratigraphy where lithology is the dominant control and conversely suggests areas where faults and fractures may influence groundwater movement. This analysis has direct consequences for evaluation of contaminant flow and transport beneath Tinker Air Force Base and characterization of the Central Oklahoma Aquifer in general.