Geology

Ozark Aquifer Geology: The St. Francois Mountains of southeastern Missouri are the remnants of an igneous regional continent building process (Imes and Emmet, 1993). They crop out above the surface in south east Missouri and descend underneath the surface into neighboring states as a confining basement layer to the entire aquifer system (Denison et al., 1984). Those parts that are deeply buried with sediments and also have a partly metamorphized composition that is also part of the confining. These layers include rhyolites, granite, and associated weathered sediments of Precambrian origin. Volcanic materials are dated at 1.2 to 1.3 billion years before present. Emplaced plutonic rocks have been dated between 1.4 to 1.5 billion years before present (Denison et al., 1984) . A view of this Precambrian layer is presented in Figure 3. A conceptual model of the Aquifer that lies in the basement rock is presented in Figure 4.