Mantle plumes and flood-basalt stratigraphy in the Paraná, South America

Geochemical studies of the Paraná continental flood basalts in Brazil have led to the recognition of distinct magma types, which have been used to infer the internal stratigraphy of the lava pile. The overstepping of stratigraphic units toward the north and a similar compositional change in sills within the underlying Paraná basin sedimentary rocks imply that the site of magnatism migrated ∼750 km toward the north during this volcanic event. This has important implications for recent plume-related models that have argued whether fithospheric rifting must accompany the presence of a mantle plume in order to generate continental flood-basalt magmatism. It is difficult to ascribe the magnitude and direction of the shift in the locus of the Paraná magmatism to movement of the Brazilian lithosphere relative to the underlying Tristan mantle plume. Instead, it is suggested that the observed lava distribution and internal structure of the Paraná-Etendeka flood-basalt province were imposed by the intracacies of the rifting process during the initial opening of the South Atlantic Ocean.