DEVELOPMENT OF THE SIERRA GERAL-R/O GRANDE RISE HOT SPOT TREND

The Serra Geral-Rio Grande hot spot trail developed as a sequence of three major periods of volcanic effusion each followed by a rift propagation event (Figure 1). The three volcanic effusion events created the Serra Geral, Sao Paulo Plateau and the Rio Grande Rise. The.succeeding rift propagation episodes occurred during the Neocomian South Atlantic initial rift (Rift Al, the Late Aptian eastward spreading center jump to the Angolan margin (Rift B), and the Campanian to Maestrichtian propagating rift generation of the Central and southern Walvis Ridge (Rift C). The net effect of the rift propagation events was to transfer southeastward the right lateral offset in the South Atlantic rift manifested by the Cabo Frio- Angra dos Reis Embayment. It is proposed that these spreading center readjustments are imposed by isostatic readjustments due to loading of basaltic piles upon weak lithosphere. There is a correlation between the effusion/rift events during the Serra Geral-Rio Grande hot spot evolution and the rates of extinction for marine fauna. This correlation may be spurious or it may reflect the effect of terrestrial tectonic processes on faunal evolution.