Field works. Example 6.
Delineate the boundaries between limestone and dolomite
Electrical tomography survey was conducted to delineate the boundaries between limestone and dolomite. On geoelectric model the high-resistivity layer is clearly visible. This layer associates with dolomite (underlayment of limestone). Dolomite is reflected by lower porosity and higher resistivity values than limestone.
The low-resistivity marl underlies the dolomite. The upper layer thickness of the model is 1 m. This layer corresponds to the near-surface rocks of different composition. Deeper, there is a layer of clay, which has the resistivity values from 60 to 100 Ohm-m. The thickness of this layer varies from 2 to 4 m. Comparison of geoelectric model and borehole data shows that limestone layer (the thickness is 6 m) is reflected by high resistivity values. The depth to the top of the layer is around 4-6 m. Deeper, there is dolomite of a much higher resistivity. Resistivity values decrease with the depth 120-460 Ohm-m because of low-resistivity marl underlies the dolomite. Electrotomography data were processed with the use of ZondRes2D.