Reevaluation of plate motion models based on hotspot tracks in the Atlantic and Indian oceans

Plate motion models based on hotspot tracks in the Atlantic and Indian Oceans predict minimal movement (less than a few millimeters per year) between these hotspots and their counterparts in the Pacific Ocean for the past approximately 100 m.yr., whereas plate circuit exercises indicate relative motions of approximately 20 mm/yr. Hotspot-based models also suggest that the Rajmahal Traps, India, were located approximately 1000 km away from the Kerguelen hotspot at approximately 115 Ma, and the Deccan Traps, India, were located a similar distance from the Reunion hotspot at approximately 65 Ma; this is at odds with conclusions derived from paleomagnetism, plate circuits, and geochemical parameters that suggest a genetic link between flood basalt provinces in India and hotspots in the Indian Ocean. These divergent views may be explained by plume action approximately 1000 km from its center or errors in the hotspot motion models. The latter hypothesis is scrutinized in this article by examination of the radiometric ages for hotspot tracks in the Atlantic and Indian Oceans. The (super 40) Ar/ (super 39) Ar step-heating data for rocks defining the tracks of the Reunion and Kerguelen hotspots in the Indian Ocean and the Great Meteor and Tristan da Cunha hotspots in the Atlantic Ocean are critically reexamined. Of approximately 35 such ages utilized for deriving plate motion models for the past 130 m.yr., at best, only three ( approximately 32, approximately 50, and approximately 52 Ma) in the Indian Ocean and one ( approximately 65 Ma) for the Atlantic Ocean may be treated as crystallization ages. Conclusions based on hotspot track modeling for Late Cretaceous to Eocene time are suspect, and those for the Early to Late Cretaceous period are untenable. In the absence of precise age data for the tracks of hotspots in the Atlantic and Indian Oceans, and inconsistent age progressions noted within a single volcanic chain, plate circuit models serve as the superior technique for tracing plate motions over the past approximately 100 m.yr. The degree of (absolute) motion for hotspots remains contentious. For most hotspots, models indicating detectable movement (>20 mm/yr) for the past approximately 100 m.yr. are favored; the Kerguelen plume was situated close to its current position (49 degrees S) at approximately 115 Ma.