Extensional tectonics and the fragmentation of Gondwanaland

Summary Evidence of widespread lithospheric extension, bimodal volcanism, and uplift and erosion, accompanying the fragmentation of Gondwanaland, is reviewed. One regime of extensional phenomena appears to be intimately associated with a Pacific-margin convergent-plate regime. A second appears to bear no direct geometrical relationship to the margin, but may reflect a thermal anomaly that resulted in the breakup of Gondwanaland. Possible causes of this anomaly are discussed. The two regimes overlap in space and time in the South Atlantic-Weddell Sea area. A causal relationship between the two is possible but remains non-proven.