Was there a global-scale plate reorganisation event at 100 Ma?

A plate reorganisation event that occurred at 50 Ma has received much attention due to its association with the well-known bend in the Hawaiian-Emperor seamount chain. We review the major tectonic events that occurred between 110 and 90 Ma and find strong evidence that a plate reorganisation at this time was global in scale, occurred over a period of 3-8 Myr, and may have been more dramatic than the 50 Ma event. While the Hawaiian-Emperor bend is synonymous with the 50 Ma event, prominent fracture zone bends in the Wharton Basin west of Australia record a drastic 50° change in the direction of spreading between Australia and India, and have long been discussed in terms of a mid-Cretaceous plate reorganisation in the Indian Ocean. Yet to-date there has been no attempt at a complete global investigation of this reorganisation to determine its magnitude and continental impact. Key tectonic events in the Atlantic-realm include a major compressional episode in the Antarctic Peninsula, a 75° counter-clockwise rotation of the Antarctic-South American spreading ridge in the Weddell Sea, an increase in spreading rate at the mid-Atlantic ridge, a change in the tectonic regime along the western convergent margin of South America from extensional to compressional, a subduction polarity reversal in the Caribbean, and changes in sedimentation patterns in African basins followed by a kimberlite emplacement pulse. The Indian-Pacific realm records back-arc basin closure, a magmatic pulse and a possible spreading ridge subduction event in the NeoTethys as well as rapid clockwise rotation of the Indian-Antarctic spreading ridge, the termination of long-lived eastern Gondwanaland subduction east of Australia, a swerve of the Pacific plate, a major unconformity in New Zealand, and a change in the geochemistry of igneous rocks in Marie Byrd Land (West Antarctica) signifying a transition from subduction-related to rift-related magmatism. The concentration of tectonic events occurred in the reconstructed-southern hemisphere, thereby signifying that the ultimate trigger for the reorganisation was located in the southern hemisphere. We describe two potential driving mechanisms for the 100 Ma event: (1) termination of the long-lived eastern Gondwanaland subduction zone (a top-down mechanism), and (2) intersection of the Bouvet Plume with the Africa-South America-Antarctica ridge-ridge-ridge triple junction (a bottom-up mechanism). Our review of the 100 Ma reorganisation may help in re-assessing the driving forces of global tectonic events and aid hypothesis testing using geodynamic models, including those for the 50 Ma event.