Mapping depth to bedrock on a glaciated landscape with ground-penetrating radar

Collins, M.E.; Doolittle, J.A.; Rourke, R.V.

Mapping depth to bedrock on a glaciated landscape with ground-penetrating radar

1989

Collins, M.E. | Doolittle, J.A. | Rourke, R.V.

In many upland areas on glaciated landscapes, it is difficult to examine soil profiles and determine the depth to bedrock. Glacial rock fragments and irregular or weathered bedrock surfaces limit the effectiveness of auger techniques. While general trends can be inferred from the landscape, depth to bedrock or thickness of till cannot be accurately predicted from landscape position alone. Therefore, ground-penetrating radar (GPR) was used to map the depth to bedrock for two study sites in Maine. Data were used to (i) determine the variability of the depth to bedrock in similar delineated areas of a map unit, (ii) compare the accuracy of GPR with auger methods, and (iii) evaluate the performance of GPR on a glaciated landscape in Maine. Results were confirmed by studying a trench excavated to bedrock. These results indicated that GPR techniques were more reliable and effective than conventional auger techniques for determining the depth to bedrock, and thus for determining the composition of map units that are based on soil-depth criteria. Additionally, the screw auger was shown to be an unreliable tool for determining soil depths in moderately coarse-textured tills having large amounts of coarse fragments.

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