CENOZOIC SUBSIDENCE AND UPLIFT OF CONTINENTS FROM TIME-VARYING DYNAMIC TOPOGRAPHY

Time-varying global dynamic topography has been computed for the entir e Cenozoic, The spherical viscous-flow model is driven by a distributi on of density heterogeneity based on Mesozoic and Cenozoic subduction. By using the calculated topography, the uplift and subsidence histori es of five regions fixed to the North American, Indian, Australian, In donesian, and South American continents are computed. Predicted vertic al motions are in qualitative agreement with observed values except fo r India and South America. For Australia and North America, the predic ted 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 Ku la plate subduction after 48 Ma. Dynamic topography depends on the vis cosity structure of the mantle; a lower mantle that is 50 times more v iscous than the upper mantle yields the best agreement between modeled and predicted vertical motions. The presence of a low-viscosity chann el beneath the lithosphere has only a small influence on our results. Compared to dynamic topography, the time-varying geoid is insignifican t in controlling relative sea level.