Noise in the Cretaceous Quiet Zone uncovers plate tectonic chain reaction

Abstract

Global plate reorganizations, intriguing but loosely defined periods of profoundly changing plate motions, may be caused by a single trigger such as a continental collision or a rising mantle plume. But whether and how such triggers propagate throughout a plate circuit remains unknown. Here, we show how a rising mantle plume set off a ‘plate tectonic chain reaction’. Plume rise has been shown to trigger formation of a subduction zone within the Neotethys Ocean between Africa and Eurasia at ~105 Ma. We provide new constraints on Africa-Eurasia convergence rates using variations in geomagnetic ‘noise’ within the Cretaceous Normal Superchron (the 126-83 Ma period without magnetic reversals) recorded in the Atlantic Quiet Zones crust. These new constraints are consistent with the timing of numerically predicted African Plate acceleration and deceleration associated with onset and arrest of the intra-Neotethyan subduction zone. The acceleration was associated with a change in Africa-Eurasia convergence direction, which in turn was accommodated by a next subduction initiation at ~85 Ma in the Alpine region that cascaded into regional tectonic events. Our concept of plate tectonic chain reactions shows how changes in plate motion, underpinned by mantle dynamics, may self-perpetuate through a plate circuit, making global plate reorganizations a key to unlock the driving mechanisms behind plate tectonics.