Parana flood basalts; rapid extrusion hypothesis confirmed by new (super 40) Ar/ (super 39) Ar results

The duration of volcanism in the Parana continental flood basalt (CFB) province, essential information to assess models of melt generation, eruption rates, continental breakup, and volcanism-driven extinction events, remains unresolved due to conflicting sets of (super 40) Ar/ (super 39) Ar geochronology data. Some results suggest that the Parana CFB volcanism began at 134.7+ or -1 Ma and lasted <1 m.y. Another set of results reveals an extrusion interval of 11 m.y., from ca. 140 Ma to ca. 129 Ma. To resolve this controversy, we reanalyzed three of the exact hand specimens that previously yielded the oldest and youngest ages in the protracted 11 m.y. range. Our new ages are statistically indistinguishable from each other and the previous 134.7+ or -1 Ma result and indicate a short eruption event. A rapid extrusion for the Parana CFB and the lack of a major contemporal extinction event challenge proposed direct links between CFB volcanism and mass extinctions and refute petrological models that rely on a protracted extrusion of the Parana CFB.