The natural remnant magnetism in rock bodies. The permanent magnetization acquired by rock that can be used to determine the location of the magnetic poles and the latitude of the rock at the time it became magnetized.
Tarbouk, E.J. & F.K. Lutgens, (2006), EARTH, 8th edition, Pearson Education International.
The study of ancient magnetic fields, which are preserved in the magnetic properties of rocks. ie. studying the changes in position of the magnetic poles, as well as reversals of poles in the geological past.