UTILIZING MULTIPLE GEOPHYSICAL TECHNIQUES TO ANALYZE BEDROCK GEOMETRY AND SEDIMENTOLOGICAL CONTROLS ON RIPARIAN MEADOW COMPLEXES IN THE CENTRAL GREAT BASIN, NV

Riparian meadow systems in the Central Great Basin are of interest because they support the majority of ecosystem diversity in the region. These systems are actively degrading due to incision of the through-going streams, which results in a lowering of the water table and resultant modification of the flora. Bedrock geometry and sediment variability in the meadow complexes are important because of their control on the overall hydrology of the system. We hypothesize that the sediments associated with side-valley alluvial fans and fault-related bedrock steps interact to constrict ground water flow and have a dominant influence on the hydrology. Testing this hypothesis (or alternatives that result from examining the data) is critical in the development of a management plan for protecting and restoring existing meadow complexes.

Three geophysical techniques are used in conjunction to analyze the bedrock/sediment interaction involved in the formation of these riparian complexes. Seismic reflection data and seismic refraction tomography data were collected to analyze bedrock structure and topography, while ground penetrating radar (GPR) data were collected to determine the stratigraphic variability. Over 8 kilometers of seismic profiles and over 70 GPR profiles in 6 different riparian meadow complexes were collected over three summers of field work (2003-2005). These data are combined with existing borehole data to ground-truth the geophysical data. These three techniques together are useful because they provide more hydrogeologic information than could be obtained with only one technique. This “data fusion” methodology may also be applied to other geologic and hydrologic settings, such as fluvial or glacial environments.