MANTLE PLUMES LINK MAGNETIC SUPERCHRONS TO PHANEROZOIC MASS DEPLETION EVENTS

Abstract

The four most recent large mass extinction events in the Phanerozoic - the Cretaceous-Tertiary (KT), the Triassic-Jurassic (TJ), and the Permo-Triassic (PT) and Guadalupian-Tatarian (GT) doublet - are associated with a major flood basalt eruption, with the timing of peak volcanic activity corresponding within measurement uncertainties to the extinction event. Three magnetic superchrons precede the four largest Phanerozoic extinctions. The Cretaceous Long Normal Superchron (duration ~ 35 Myr) precedes the KT and the Permian Kiaman Long Reversed Superchron (~ 50 Myr) precedes the PT-GT doublet. In addition, the newly recognized Ordovician Moyero Long Reversed Superchron (~ 30 Myr) precedes the end-Ordovician extinction event. There is a 10-20 Myr delay between the end of each superchron and the subsequent mass depletion event, both of which represent distant outliers from their respective populations. We propose that deep mantle plumes link these seemingly unrelated phenomena. Long-term (~ 200 Myr) variations in mantle convection possibly associated with the Wilson cycle induce temporal and spatial variations in heat flow at the core-mantle boundary. Polarity reversals are frequent when core heat flow is high and infrequent when it is low. Thermal instabilities in the D"-layer of the mantle increase core heat flow, end the magnetic superchron, and generate deep mantle plumes. The plumes ascend through the mantle on a 20 Myr time scale, producing continental flood basalt (trap) eruptions, rapid climatic change, and massive faunal depletions. © 2007.