Surficial geophysical data for two cross-valley lines in the middle Eagle River valley, Alaska

In 1979, six electrical resistivity and four seismic refraction soundings were made in the middle reach of the Eagle River valley northeast of Anchorage, Alaska. Interpretation of the geophysical data collected indicated that depth to bedrock below the valley floor varies between about 350 and 450 feet. Two, and perhaps three, major unconsolidated sedimentary layers are inferred to overlie bedrock, although other significant layers may not have been recognizable. No prior subsurface data were available in this area. A resistivity sounding was made also at a site about 7 miles downstream to explore for a buried bedrock channel. The data here indicated that the bedrock surface is about 50 feet above sea level. Hence, the hypothesis of a buried ancient outlet valley of Eagle River at this location gained more credence. (USGS)