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

André Revil (1, 2) , L. Cary (3) , Q. Fan (1) , Anthony Finizola (4, 5) , F. Trolard (3)

1 CEREGE - Centre européen de recherche et d'enseignement des géosciences de l'environnement
2 ISTerre - Institut des Sciences de la Terre
3 URGSE - Unité de recherche Géochimie des Sols et des Eaux
4 Instituto Nazionale di Geofisica e Vulcanologie Sezione di Palermo
5 LGSR - Laboratoire GéoSciences Réunion

The flow of ground water in a buried permeable paleochannel can be observed at the ground surface through its self-potential signature. We apply this method to delineate the Saint-Ferre´ol paleo-channel of the Rhone River located in Camargue, in the South East of France. Negative potentials, ~-30 mV (reference taken outside the paleochannel), 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.

Mots clés: TENEUR EN EAU DU SOL; CANAL A EAU

Domaines: Géophysique [physics.geo-ph]

André Revil, L. Cary, Q. Fan, Anthony Finizola, F. Trolard. Self-potential signals associated with preferential ground water flow pathways in a buried paleo-channel.. Geophysical Research Letters, 2005, 32 (7), pp.L07401. ⟨10.1029/2004GL022124⟩. ⟨hal-01452536⟩