Rapid South Atlantic spreading changes and coeval vertical motion in surrounding continents: Evidence for temporal changes of pressure-driven upper mantle flow

摘要: The South Atlantic region displays (1) a topographic gradient across the basin, with Africa elevated relative to America, (2) bimodal spreading history fast rates in Late Cretaceous and Eo-Oligocene, (3) episodic regional uplift events adjacent continents concentrated Oligocene. Here we show that these observations can be linked by dynamic processes within Earth's mantle, through temporal changes asthenosphere flow beneath region. implies westward, pressure-driven mantle while rapid rate changes, on order 10 million years, require significant decoupling of plate motion from large-scale buoyancy distribution mechanically weak asthenosphere. Andean growth late Miocene explain most recent velocity reduction, arising increased boundary forcing associated newly topography. But this mechanism is unlikely Cretaceous/Tertiary variations, as paleoelevation at time are small. We propose an unsteady component variations. Temporal due pressure gradients imply correlation horizontal vertical motions: find prediction our models agrees geologic geophysical region, including episodes passive margin uplift, basin reactivation, magmatic activity.