A pulse of ocean crustal production during the mid-Cretaceous begins at the same time that magnetic reversal frequency drops to zero. We suggest that slab penetration into the lower mantle caused a thermal boundary layer normally at 670 km to be rapidly advected upward as the slabs descended through the lower mantle. The onset of near-surface melting due to the rise of this boundary layer coincides with the slabs' arrival at D″, which drove up the heat flux across the core-mantle boundary and stabilized the magnetic reversal process. The slab penetration event was coincident with the breakup of the Gondwana supercontinent and triggered the subsequent formation of oceanic plateaus in the central Pacific and Indian Ocean basins.

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