This preserves a record of the Earth's magnetic field at the time the mineral was laid down as sediment or crystallized in magma and also the tectonic movement of the rock over millions of years from its original position.
The main difficulty that arises is if the rocks has significant weathering or are overlayed with thick layers of sediments.
This created the baked contact test that was able to find relative ages in the areas of igneous rocks.
(Neil Opdyke, 1996) There are several kinds of natural remnant magnetism that can occur in a sample.
A commonly cited mechanism of isothermal remanent magnetization acquisition is through lightning strikes.
[2] Marine oil-bearing sandstones are physically unstable mineralogies whose low-field susceptibility and isothermal remanent magnetization increase irreversibly, even after weak mechanical shocks and an AF demagnetization in 100 mT peak alternating fields.
(Pick, 1991) A study was also conducted exploring when magnetite went under low-temperature oxidation to a maghemite.