Duration of Parana magmatism and implications for the evolution and source regions of continental flood basalts

Duration of Continental Floods Basalts magmatism has generally been considered to be extremely short. Ar-Ar data for different magma type, over a broad region within Parana, demonstrate a duration of 10 Ma, an order of magnitude greater than the usually accepted duration of magmatism. The dating method included rigorous geochemical selection tests, to discard altered samples, combined with the analysis of laser spot technique using the isochron approach. This methodology allows discrimination between rocks which yield precise ages and those which are too altered or heterogeneous. The agreement between the determined age and the relative stratigraphic position of samples supports the above statement. 4 figs