Extended Data Fig. 8: Example demagnetization results from this study that show a reversed, transitional and normal polarity for samples RB45, 47 & 49 from Rainbow Beach.

Left-hand column: plots of NRM intensity with respect to demagnetization step with data points after alternating field demagnetization (AFD) in blue squares and thermal demagnetization (ThD) in yellow circles; green lines indicate data portions used for PCA fitting of ChRM directions. Right-hand column: vector demagnetization diagrams from which declinations (blue circles) and inclinations (yellow squares) are determined by fitting a ChRM using PCA through multiple demagnetization points. Linear PCA fits are shown with orange lines for the inclination and green lines for the declination. Results shown above highlight example results for reversed, transitional and normal polarities for samples (a, b) RB45-5 (transitional polarity with southward declinations and downward inclinations); (c, d) RB47-10 (reversed polarity); (e, f) RB47-11 (reversed polarity); and (g, h) RB49-11 (a normal polarity sample from a site with generally unclear results). For remaining demagnetization results the reader is referred to the Supplementary Figs. 1–2.