Intra-Antarctic plate divergence: No signal in the Hawaii–Emperor bend

Cenozoic plate divergence across the West Antarctic Rift System, important for understanding the role of Pacific plate motion in generating the prominent ∼47 Ma bend in the Hawaii–Emperor seamount chain, is inferred and calculated using model estimates of relative motions between the plates of eastern and western Antarctica and their neighbours. Problematically, basin-fill and melt products that might confirm inferred pre-bend divergence are unknown, whilst calculations of post-bend motion have come to infer much of the rift system in the deep Antarctic interior was a collision zone. This work presents updated plate kinematic models based on improved satellite altimeter data that combine, within estimated confidence and at high temporal resolution, to replicate the extent of subglacial extensional rift basins in West Antarctica and the mid-Eocene (∼45 Ma) maximum ages of Cenozoic magmatic rocks associated with them. Consistent with the absence of older rift-related rocks, the new models do not recapitulate their predecessors’ inferences of a Paleocene onset or phase of intra-Antarctic divergence, but may instead offer a context to diverse lines of evidence for pre-Eocene plate convergence within Zealandia. Without Paleocene divergence in Antarctica, absolute motion of the Pacific plate can be expected to have changed little at the time of the Hawaii–Emperor bend, as implied by the uneventful Pacific–Antarctic relative motion path derived from the new models. Future work on the causes of the bend should therefore focus on processes responsible for migration of the Hawaii hotspot relative to the Pacific mantle.