In 1972, Archaeomagnetic studies were carried out on the prehistoric aboriginal fireplaces found along the ancient shoreline of Lake Mungo. Magnetization preserved in oven-stones and baked hearths show that the axial dipole field moved up to 120 degrees from its normal position around 30,000 years ago. This is called a geomagnetic excursion. Because most of the excursions found before Lake Mungo were in sedimentary material, it had been thought that the magnetic field directional anomalies were detrital or diagenetic in origin. The Lake Mungo results were due to thermoremanent magnetization, ruling out a sedimentological phenomena.