Plate kinematics of the South Pacific since the Late Cretaceous: resolution 
of the fast-slow hotspot controversy

Rupert Sutherland
Institute of Geological and Nuclear Science, New Zealand


Abstract:
Available data suggest that Indo-Atlantic hotspots have moved slowly (<2 cm/yr), 
relative to each other, since the Late Cretaceous. Pacific hotspots have also moved 
slowly, relative to each other, since the Late Cretaceous. Global plate-motion 
circuits show that Indo-Atlantic hotspots have moved slowly relative to Pacific 
hotspots since the mid-Eocene. All the motions described above can be predicted 
with reasonable models of mantle convection that include plume advection.

However, existing plate kinematic models predict very rapid movement of Pacific 
hotspots (8 cm/yr), relative to Indo-Atlantic hotspots, during the interval 83-43 
Ma. Why was this period of time so different, or why are the inferences of hotspot 
motion so inaccurate?

I will show that a reconciliation of the South Pacific plate-motion circuit may 
resolve this controversy. Feasible kinematic models that include plate motions at 
boundaries that are now hard to quantify (e.g. within continental Antarctica and 
New Zealand) reduce predicted hotspot velocities to within the range output from 
mantle convection models. Motions at the "missing" boundaries allow closure of the 
South Pacific plate-motion circuit and provide a reasonable explanation for 
observed crustal structure in the region.