Extended Data Fig. 9: Backtracked original eruptive locations for Samoa and Cook-Austral-related volcanoes (Cook-Austral, Samoa, Tuvalu, Gilbert, Wake, Magellan, Tokelau), using various absolute plate motion models.

A) this study; B) Koppers01¹⁸; C) Wessel08⁴¹; D) Doubrovine12⁶. Backtracked seamounts color-coded (lower left panel) for their isotopic compositions show that at present-day hotspots (purple text) are the focus of clusters of consistent geochemical compositions, defined by grey (2) and purple (1) contours for Gaussian-kernel probability density estimates for the backtracked locations. Insets show these density contours and the running mean of backtracked location and age to estimate plume motion from model mismatch from fixed hotspots (a-d). Backtracked (grey symbols⁶) locations for Hawai‘i (E) and Louisville (F) and their smoothed age-track (wide yellow or orange) highlight a deviation from predicted plume motion (S04/red¹⁰⁰ and D12/purple⁶) beyond 50 Ma, indicating a mismatch for plate motion models into the Cretaceous. Outlines show Ontong-Java Plateau (OJP) backtracked with the new model overlap with Louisville, where stars show approximate center of Ontong-Manihiki-Hikurangi. Red arrows show smoothed tracks match derived latitudinal plume motion from paleomagnetic latitudes^13,96. Backtracking of OJP assumes fixed relationship to the Pacific plate, with no rotation of the plateau¹¹.