Fig. 4: Non-geocentric axial dipole field (Interval III).
From: Late Cambrian geomagnetic instability after the onset of inner core nucleation
Spherical density distribution and k-means cluster analysis of virtual geomagnetic poles (VGPs) following Bono et al.49, shown in orthographic projection centered on −30°, 280° E. Spherical contouring uses a uniform grid of nodes with a median distance of 4° and a counting radius of 10°. Color intensity corresponds with the density of directions within the counting radius (value shown in color scale). Circles: individual VGPs, color corresponds with cluster mode assignment. Red circles show directions identified as outliers. Stars: k-means cluster centers for each mode. Modes are as follows: Mode I (blue) 257.9° E, −62.3°; Mode II (gold/yellow) 224.9° E, −28.2°; Mode III (green) 337.1° E, −52.4°. Open diamond: Stable reversed polarity mean VGP from the Jiangshanian GSSP section (Interval II) with A95 circle of confidence. Solid triangle: Stable normal polarity VGP mean antipode (Interval IV), with A95 circle of confidence. Green arrows highlight the angular distance between the stable reversed polarity VGP and Mode II, and the angular distance between Mode II and the stable normal polarity (antipode) VGP.
