Rapid eruption of silicic magmas from the Parana magmatic province (Brazil) did not trigger the Valanginian event

Abstract

The Valanginian Stage is marked by a period of global positive delta C-13 carbon cycle perturbation and biotic crises, which are collectively referred to as the Valanginian event (VE). Many attempts have been made to link the Parana-Etendeka large igneous province volcanism with the VE. However, currently there is no conclusive proof to support this hypothesis, since the timing and duration of the volcanic activity are not known with sufficient precision. In this study, we significantly revise the time scales of magmatism and environmental impact of the Parana magmatic province (PMP) in Brazil with new high-precision zircon U-Pb ages from the low-Ti Palmas and high-Ti Chapeco sequences. Our data demonstrate that significant volumes of low-Ti silicic rocks from the PMP erupted rapidly at ca. 133.6 Ma within 0.12 +/- 0.11 k.y. The age of the high-Ti Chapeco sequence from central PMP is constrained at ca. 132.9 Ma and thus extends the duration of magmatic activity by similar to 700 k.y. Our new ages are systematically younger than previous ages and postdate the major positive carbon isotope excursion, indicating that PMP silicic magmatism did not trigger the VE but could have contributed to extending its duration. Within the framework of the stratigraphic column of the PMP, the earliest low-Ti basalts could have been responsible for the VE if they are at least 0.5 m.y. older than the low-Ti silicic rocks dated herein.