Paleomagnetic Logging Tool
Geological High-Resolution Magnetic Tool (GHMT, Schlumberger).
The Geological High-Resolution Magnetic Tool (GHMT, Schlumberger) makes two measurements needed to determine the polarity of the remanent magnetism: The total magnetic field and the magnetic susceptibility.
Laboratory of Geoscience and Engineering, Faculty of Civil Engineering and Geosciences, Stevinweg 1, Delft, (building #23).
Polarity Determination, statistical approach.
The principle of paleomagnetic logging is based on detecting the polarity reversals of the remanent magnetization imparted onto the rocks by the Earth’s magnetic field. It is based on a statistical approach, since directly measuring such a very small vectorial quantity is not possible. If the measured susceptibility and the computed remanent component correlate over a vertical window, it is assumed that the polarity is normal while the opposite indicates a reverse polarity (for a given scenario, depending on the latitude, the layer dips etc.).
A susceptibility and a total magnetic field measurement are made with great precision, because a very small signal needs to be detected compared to the Earth’s total magnetic field.