Fig. 2

a Sketch of thermal remanence acquisition in an igneous rock. Magnetite spin axes are randomly distributed in a crystallizing magma at 1,000 °C. b As the rock cools below the Curie temperature of magnetite, the spin moments align with the ambient Earth's field and become locked into the rock. c Idealized sketch of detrital remanence acquisition. As the magnetic particles fall through the water column, they show no preferential alignment due to small currents and eddies within the water column (point (1)), at point (2), the particles reach the sediment water interface and begin to align with the ambient field though some minor disturbance is possible due to bioturbation or other small currents/eddies within the slurry, and at point (3) the mineral grains become permanently aligned and “locked-in” with the ambient field