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Detailed geologic mapping is being conducted by the USGS in and adjacent to the Buffalo National River, a park administered by the National Park Service, to better understand and characterize the natural resources and associated ecosystems of this area within the Ozark Plateau region. General-purpose geologic maps are created to provide a framework for a host of natural resource, natural history, and public education uses. The mapping activities focus on understanding development of karst features and ground water flow paths through extensive karst aquifers within Ordovician through Pennsylvanian rock strata that underlie the Buffalo River watershed.
The geologic maps provide background to understand major cave resources in the park, geologic controls on major spring locations, and recharge areas for springs, including recharge basins that extend beyond the surface watershed boundaries of the Buffalo River.
(Research funded by Geologic Framework of the Southern Ozark Plateaus Project, USGS National Cooperative Geologic Mapping Program and National Park Service Water Resources and Geologic Divisions)
The geologic mapping helps place inventories of springs and caves within the park in proper stratigraphic context. Caves and springs are present in a variety of geologic formations ranging in age from Ordovician to Pennsylvanian, but they are concentrated within the 120-m-thick, Mississippian-aged limestone of the Boone Formation. Springs (fig. 5) in the western part of the park are most frequent near the unconformable contact between the basal St. Joe Member of the Boone Formation and underlying sandstone-rich Ordovician Everton Formation. These features indicate that the Boone Formation, comprising the karstic Springfield aquifer, is the principal path for ground-water flow into the western Buffalo River watershed. New mapping documents that major springs and cave systems are localized in structural lows (fig. 6) of the Boone Formation where ground water discharges at lowest elevations within the perched Springfield aquifer. Dye-tracer studies indicated that some springs localized in structural lows have captured recharge from beyond topographic watershed boundaries (fig. 7). This interbasin flow of ground water becomes a land management concern if agricultural land use of adjacent watersheds results in transfer of nutrient-enriched ground water in the Buffalo River.
New geologic mapping in the middle part of the Buffalo River documents a transition from the Springfield Plateau aquifer to lower karstic Ordovician formations of the Ozark aquifer. The largest spring in the park, Mitch Hill Spring (fig. 8), discharges from a stratigraphic level in the lowest part of the Ordovician Everton Formation above impervious argillaceous dolostone of the Powell Dolomite that is brought to the surface along the Buffalo River in a structural high. Dye tracer studies integrated with the geologic mapping are investigating probable pathways for ground water between the two aquifers.
New geologic mapping has recognized many new faults and folds in the region and has added information on the age and character of new and previously recognized faults. These data are revealing new insights into the ancient history of deformation in the area that was probably related to past interactions among tectonic plates in late Paleozoic time.
Results of these mapping efforts were presented to fieldtrip participants at the Geological Society of America North Central/South Central section combined meeting in April 2010. Mark Hudson and Kenzie Turner of the USGS and Chuck Bitting of the National Park Service led the field trip to emphasize geologic controls on karst development in the Buffalo National River area (fig. 9).
Below are publications associated with this project.
Below are partners associated with this project.