A STUDY CORRELATING STRATIGRAPHY AND GEOPHYSICAL TECHNIQUES ON A MISSISSIPPI RIVER BLUFF-LINE ALLUVIAL FAN IN PANOLA COUNTY, MISSISSIPPI

The portion of the Mississippi River alluvial aquifer underlying the Delta region of Mississippi is a threatened natural resource with groundwater withdrawals exceeding local recharge rates. The largest groundwater withdrawals in the Delta region are used to support agricultural and aquacultural activities. Bluff-line deposits, in the form of alluvial fans, may be crucial recharge areas and may provide valuable clues to stratigraphic and hydraulic connectivity between the Mississippi River alluvial aquifer and older deposits of the bluff. The goal of this project was to correlate near surface geophysical data with the shallow stratigraphy (upper 3 meters) of an alluvial fan in Panola County, Mississippi. Geophysical techniques included ground penetrating radar (GPR) and ultra-shallow shear-wave seismic reflection. GPR data were collected using a pulseEKKO PRO with a 100 Mhz antenna. Reflection data were collected using a 24-channel seismograph and a 0.5 kg claw hammer and a small triangular block of wood as an energy source. Sediment samples were collected by hand augering at the two locations of the seismic lines. Samples were air-dried, sifted to determine grainsize distribution, and described texturally under a microscope. The sampling location nearest the apex of the fan showed a greater variation in grainsize than the distal location. Preliminary interpretation of the seismic reflection and GPR data set from the apex of the fan indicates that a strong reflection correlates with a shallow gravel layer; however no strong shallow reflections were identified in the data set from the distal location.