Bounds on global dynamic topography from Phanerozoic flooding of continental platforms

Abstract

The movement of continents with respect to a large-scale pattern of dynamic topography and geoid, imposed by convection in the mantle, must contribute to the flooding of continental platforms. Here I investigate this phenomenon, using a one-dimensional model in which a continent moves from a high to a low of dynamic topography (and geoid), and in the process is partially exposed and then flooded. If the dynamic topography is greater than about 150 metres, the model continent is flooded by more than 3 0%—the maximum amount of flooding experienced by North America during the entire Phanerozoic eon1. The model suggests that a large-scale pattern of dynamic topography must have an amplitude of less than 150 metres, and that the admittance, the ratio of geoid to dynamic topography, may be greater than 0.3. Recent models of global mantle dynamics 2,3 which predict the long-wavelength geoid from mantle seismic structure are apparently inconsistent with Phanerozoic flooding.

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