Self-potential signals associated with preferential ground water flow pathways in a buried paleo-channel

The flow of ground water in a buried permeable paleo-channel can be observed at the ground surface through its self-potential signature. We apply this method to delineate the Saint-Ferreol paleo-channel of the Rhone River located in Camargue, in the South East of France. Negative potentials, similar to-30 mV (reference taken outside the paleo-channel), are associated with ground water flow in this major sand-filled channel (500 m wide). Electrical resistivity is primarily controls by the salinity of the pore water. Electrical resistivity tomography and in situ sampling show the salinity of the water inside the paleo-channel is ten times smaller by comparison with the pore water of the surrounding sediments. Combining electrical resistivity surveys, self-potential data, and a minimum of drilling information, a 3-D reconstruction of the architecture of the paleo-channel is obtained showing the usefulness of this methodology for geomorphological reconstructions in this type of coastal environment.