GROUND PENETRATING RADAR AS A METHOD FOR INVESTIGATING HETEROGENEITY IN LAKE STRATIGRAPHY

Ground penetrating radar (GPR) has become an invaluable, non-invasive tool for subsurface investigation; however, the extent to which GPR can be applied to lake basin analysis is still being explored. The purpose of this study is to assess the capacity of GPR to image heterogeneity in lake sediments caused by depositional layers (including tephra deposits) and erosional surfaces. GPR data collected at Bayhorse Lake, Custer County, Idaho reveals four prominent reflectors in the subsurface stratigraphy of the lake basin. Analysis of the data indicates the first reflector is likely produced by the interface between the lake water and sediment accumulation. Correlating sediment depth measurements from a sediment core sample collected in 2009, we speculate the second reflector may correspond with the Newberry Ash tephra dated at 1200 cal yr B.P. At the coring location, we calculate a sedimentation rate of 0.048 cm/yr based on the age of the tephra and the sediment depth calculated by the GPR data. Further research is needed to accurately identify the other two reflectors; however, older tephras have been identified in this lake basin, and may correspond with these GPR reflections. This preliminary study shows that GPR is an effective tool that can be used to assess stratigraphic heterogeneities in lake sediments.