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Geophysical investigation of antique iron furnaces: insights from modelling magnetic and VLF data
- Source: Near Surface Geophysics, Volume 2, Issue 2, Mar 2004, p. 95 - 101
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- 01 Dec 2002
- 01 Mar 2004
- 01 Mar 2004
Abstract
Magnetic and very low frequency electromagnetics (VLF) surveys at an Antique iron mine near Saales (France) revealed several large magnetic anomalies (of the order of a few hundred nT), strong electrical conductivity contrasts (10–1000 Ωm) and out‐of‐quadrant VLF phases (φ >90°).To define both the location and the vertical extent of the underground artefacts, we interpret our magnetic data with Euler deconvolution and a 2D wavelet transform that combines maps of the total field and its gradient. We also explain out‐of‐quadrant VLF phases using simple 3D EM forward modelling. A joint interpretation of magnetic, VLF and topography data enables us to locate iron‐ore exploitation trenches, Antique iron furnaces and their surrounding slags at depths between 1 and 3 m, in good agreement with results obtained during a recent road construction.