Palaeocontinental configurations and geoid anomalies

Abstract

Reconstructions of past continental configurations help our understanding of the evolution of planetary surface morphology and impose valuable constraints on the models for planetary dynamics. The problem is that although well established palaeogeographical maps now exist for Mesozoic and later times^1,2, thanks to excellent agreement between palaeomagnetic and marine-magnetic deductions, this is not true for earlier times mainly due to the lack of independent palaeogeophysical control over otherwise longitudinally-ambiguous palaeomagnetic data. The prospect of relating palaeocontinental configurations to geoid anomalies, recently raised by Anderson³, has thus given a fresh perspective to this problem. Here his continental insulation model is shown to be an inadequate explanation of the undulations of subduction-compensated geoid. Instead, the geoid highs and lows are shown to correlate well with the overall divergent and convergent plate tectonism since the middle Palaeozoic and are thus ascribed, respectively, to the ascending and descending patterns of lower-mantle convection.