Quantification of Pacific Plate Hotspot Tracks Since 80 Ma and the
Relative Timing of Eocene Plate Tectonic Events
Abstract
The motion of the Pacific plate relative to Pacific hotspots produces
age-progressive chains of volcanoes. New methods of analysis of volcano
locations and age dates using a small number of adjustable parameters
(10 per chain) are presented. Simple fits to age progressions along
Pacific hotspot chains indicate $1\sigma$ age
uncertainties of $\approx\pm$1.0 to
$\pm$3.0 Ma. Motion between the Hawaii and Louisville
hotspots differs insignificantly from zero with rates of
2$\pm$4 mm/a
(=$\pm$2$\sigma$) for 0–48 Ma and
26$\pm$34 mm/a
(=$\pm$2$\sigma$) for 48–80 Ma.
Relative to a mean Pacific hotspot reference frame, motions of the
Hawaii, Louisville, and Rurutu hotspots are also insignificant.
Therefore plumes underlying these Pacific hotspots may be more stable in
a convecting mantle than previously inferred. We find no significant
difference in age between the Eocene bends of the Pacific hotspot
chains. The best-fitting assumed-coeval age for the bends is
47.4$\pm$1.0 Ma
(=$\pm$2$\sigma$), coincident with the
initiation of the doubling of the spreading rate of the Pacific plate
relative to the Farallon and Vancouver plates. The initiation of the
Eocene slowdown of India preceded the bends and was completed after the
bends. Any causal relation of this slowdown to the Hawaiian-Emperor bend
remains obscure. On the other hand, initiation of subduction of the
Pacific plate in the west and southwest Pacific Ocean Basin likely
preceded the formation of the bends, consistent with subduction
initiation changing the torque on the Pacific plate such that it started
moving in a more westward direction thus creating the Hawaiian-Emperor
Bend.