Effects of moderate stresses on directions of thermoremanent magnetization

Experiments designed to test the effects of directed stress on the thermoremanent magnetization (TRM) of igneous and metamorphic rocks are described. Basalt and andesite specimens exhibited no anomalous directions of TRM when cooled from 600°C under uniaxial stresses of up to 350 bars. Metamorphic rocks with preferred crystallographic orientations were found to exhibit anomalous directions of induced TRM after such treatment. These anomalous TRM directions were apparently related to the lineation of the specimens rather than applied stress. Residual magnetizations of the metamorphic specimens were found to approach the direction of the magnetizing field upon progressive alternating-field demagnetization.