Late Cenozoic global pulsations in hotspot magmatism and their possible interplay with plate tectonics, Earth's core and climate

摘要

A study of the Earth's main hotspots indicates an increase in magmatism during the last 1.5 myr, supporting a previous hypothesis on global magmatic copulsation on c. 10 myr scale through the Cenozoic. A similar pattern is found for magmatism dominantly related to plate tectonics since 15 Ma. It is suggested that the inferred syncronicity in magmatism is related to two large areas under Africa and the central Pacific expressing anomalously slow S-wave velocities in the lower mantle. Heterogeneous heat flux in the fluid outer core related to the lower mantle anomalies may cause spatially related aspherical inner core growth and rotation of the inner core with respect to the lower mantle. It is speculated that the heterogeneous heat flux in the outer core can be modulated by inner core processes of aspherical growth and rotation on 10 myr scale, subsequently leading to syncronized plume pulses from the rim of the hot lower mantle anomalies. Some of the magmatic pulses appear to coincide with abrupt drops in eustatic sea level, and it is suggested that these were caused by glaciations triggered by the volcanism.