ASSESSING PACIFIC ABSOLUTE PLATE AND PLUME MOTIONS

Absolute plate motion models aim to place lithospheric motions in a geodynamic framework, and traditionally this has been accomplished by modeling hotspot chain age progressions. The discovery of significant paleolatitude anomalies along both the Emperor and Louisville hotspot-produced seamount trails has shifted modeling efforts from relying on the fixed hotspot reference frame to new frames of reference defined by moving hotspots derived from mantle circulation models. The Pacific plate has proven particularly difficult to model due to an absence of continental crust from which reliable paleolatitude observations could be made, necessitating oceanic drilling of seamount chains. Alternative approaches involve projecting Indo-Atlantic absolute plate motions into the Pacific via plate circuits and deriving global absolute plate motions for a set of moving plumes spread across many ocean basins. We examine how well these disparate absolute plate motion models fit the available geometry and age observations. We also derive the implied plume motions required to fit the observed age progressions. Our analysis includes assessments of eight published absolute plate motion models, two of which depend on modelled plume motions and one derived simply from the history of forces applied the Pacific plate, thus bypassing seamount trail data altogether. We find most inferred plume motions are plausible given rheological constraints on mantle flow, but some imply excessive plume drift rates, and not all models fit the available data equally well. Consistent with an earlier examination of absolute plate motions using ridge-spotting, we find that a geodynamic model based on slab pull forces best satisfies both age progressions and paleolatitude observations and implies a smooth and consistent history of plume motions.