Bedrock detection beneath river terrace deposits using three-dimensional electrical resistivity tomography
Chambers, J.E.; Wilkinson, P.B.; Wardrop, D.; Hameed, A.; Hill, I.; Jeffrey, C.; Loke, M.H.; Meldrum, P.I.; Kuras, O.; Cave, M.; Gunn, D.A.. 2012 Bedrock detection beneath river terrace deposits using three-dimensional electrical resistivity tomography. Geomorphology, 177-8. 17-25. 10.1016/j.geomorph.2012.03.034Before downloading, please read NORA policies.
We describe the use of a fully volumetric geophysical imaging approach, three-dimensional electrical resistivity (3D ERT), for bedrock detection below mixed sand and gravel deposits typical of fluvial valley-fill terraces. We illustrate the method through an analysis of terrace deposits of the Great Ouse River (UK), where up to 4 m of sand and gravel have filled the valley bottom during the latest Pleistocene. We use an edge detector to identify the steepest gradient in first-derivative resistivity profiles, which yields an estimate of bedrock depth (verified by drilling) to a precision better than 0.2 m (average) and 0.4 m (standard deviation). The 3D ERT method provides a high spatial resolution, which enabled a previously unknown erosional bedrock structure, associated with the change from deeper first terrace to second terrace deposits, to be identified in the Great Ouse valley. The method provides a relatively quick method to quantify terrace fill volume to a greater degree of precision than currently available.
|Programmes:||BGS Programmes 2010 > Geoscience Technologies|
|Additional Keywords:||electrical resistivity tomography|
|NORA Subject Terms:||Earth Sciences|
|Date made live:||14 Sep 2012 14:55|
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