(pÄ'lÄ-Å-mÄg'nÄ­-tÄ­z'Ém) 1  The fixed orientation of a rock's magnetic minerals as originally aligned at the time of the rock's formation. Paleomagnetism is usually the result of thermoremanent magnetization (magnetization that occurs in igneous rocks as they cool). 2  The scientific study of such magnetic remanence.