Detailed knowledge of local lithology and geological structures is essential when siting mine workings or oil wells. Although seismic reflection, especially high-resolution seismic, is the preferred method for this kind of survey, gravity and electromagnetic techniques are also vital for defining the seismic program and identifying main structural features.
Gravity
Gravity stations are easily set up in desert regions (as shown here in Tunisia). Once the data have been processed, Bouguer anomaly and residual anomaly maps can be drawn up to calculate the thickness of the sediments above the dense basement.
Electromagnetics
A copper ore body in Spain was surveyed using the EM 37 electromagnetic method, leading to the discovery of ore-rich conductive zones concealed by a hundred meters of sandstone-shale cap rock.
High-Resolution Seismic Reflection
The accuracy of images obtained with the high-resolution seismic method provides the geologist with a cross-section of local geology, directly highlighting the different layers of the salt-bearing strata.
