Cenozoic subsidence and uplift of continents from time-varying dynamic topography

Abstract

Time-varying global dynamic topography has been computed for the entire Cenozoic. The spherical viscous-flow model is driven by a distribution of density heterogeneity based on Mesozoic and Cenozoic subduction. By using the calculated topography, the uplift and subsidence histories of five regions fixed to the North American, Indian, Australian, Indonesian, and South American continents are computed. Predicted vertical motions are in qualitative agreement with observed values except for India and South America. For Australia and North America, the predicted periods of uplift and subsidence are out of phase with respect to observations, but display the correct overall trend. The latest phase of uplift for North America is directly related to the cessation of Kula plate subduction after 48 Ma. Dynamic topography depends on the viscosity structure of the mantle; a lower mantle that is 50 times more viscous than the upper mantle yields the best agreement between modeled and predicted vertical motions. The presence of a low-viscosity channel beneath the lithosphere has only a small influence on our results. Compared to dynamic topography, the time-varying geoid is insignificant in controlling relative sea level.