Outcrop of the Inglefield Sandstone and the West Franklin Limestone

Local bedrock on USI campus is of the Patoka Formation.   These sedimentary rocks are a southward-thickening unit of shale, sandstone, clay, limestone, and coal. The formation consists of all rocks above the West Franklin Limestone Member of the Shelburn Formation and below the Carthage Limestone Member of the Bond Formation (Shaver et al., 1986).  Piezometers used for this study  penetrate the Inglefield Sandstone Member of the Patoka Formation, and the Patoka Aquifer is the source of the water in the wells (Fenelon et al, 1994).  The Inglefield Sandstone Member is dominantly medium-grained quartz arenite sandstone with low angle cross beds.  This sandstone displays a fining upward sequence, and a basal paraconglomerate.  Thicknesses if the Inglefield in the study area range from 50 to 60 feet.  Archived drill logs near the study piezometer location interpret the Inglefield beginning at a depth of about 50 feet below surface elevation.    

   

Cores of the Inglefield Sandstone and the West Franklin Limestone

 The core recovered during construction of the groundwater monitoring wells shows the Inglefield extending from 52 feet to 103 feet (Elpers et al., 2002).  Horizontally oriented mica grains distributed throughout the upper portion of the Inglefield member lower the vertical hydraulic conductivity as much as two magnitudes compared to the horizontal hydraulic conductivity (Clark et al., 2002).  This anisotropy in the Inglefield Sandstone may act as the upper confining layer of the Patoka Aquifer.  At the base of the Inglefield Sandstone lies the West Franklin Limestone Member of the Shelburn formation.  The dense limestone acts as the lower confining layer to the Patoka aquifer and separates it from the underlying Shelburn aquifer (Fenelon et al, 1994).  The West Franklin Limestone Member is a Pennsylvanian biomicritic limestone noted as occurring as three distinct beds.  The limestone recovered in the core extends from 103 to 118 feet and matches the description of the lowest prominent bed.  Gravel size rounded clasts of West Franklin limestone are present in this lower section of the core.  The gravel was interpreted as being lag gravel in a paleo-erosional environment.  This interpretation also supports the identification as the lowest bed of the West Franklin Limestone as erosion has removed the upper beds prior to deposition of the Inglefield sandstone (Elpers et al., 2002).  Above the Inglefield Sandstone lies non-aquifer Quaternary age loess and unconsolidated sediment.  Localized lenses of an unnamed shale unit of the Patoka formation also exist in the study area.