Long-distance lava correlation in the Paraná volcanic province along the Serra Geral cuesta, southeastern Brazil.

The capability of determining the flow-by-flow stratigraphy and the long-distance correlation of lava flows in large continental volcanic provinces leads to a considerable advance in the understanding of processes related to generation and evolution of the lavas. The Paraná volcanic province is exposed along the Serra Geral cuesta of southern Brazil in a steeply inclined, 1,000-m-high section starting 40-m above sea level. Each of the 10-20 pahoehoe flows and rhyodacite flow units has a unique chemical composition. Integrated with field stratigraphy and gamma-spectrometric measurements, this leads to the establishment of the correct stratigraphic sequence in each of three different vertical sections. The number of flows integrating the three serras is 26 ('serra' is a mountain range in Portuguese). Each serra has basaltic andesites at the base, whereas rhyodacites are intercalated with basaltic andesites at the top. Three basaltic andesite flows and one rhyodacite flow unit are correlated between Serra Umbu and Serra Boa Vista (10 km). In the Serra Faxinal, a thick (170 m) sill at the base correlates with flow 13F, whereas a dike-sill in the Graxaim quarry (24 km distance) correlates with flow 3F. One basaltic andesite and two rhyodacite flow units correlate between Serra Faxinal and Serra Umbu (50 km). The results are most significant for the understanding of large tracts of continental volcanic provinces with use of common geochemical and gamma-spectrometric techniques. [ABSTRACT FROM AUTHOR]