Geochronology Of The Parana-Etendeka Large Igneous Province

Constraining the timing of emplacement, duration and magma extrusion rates of large igneous provinces is essential for evaluating their petrogenetic evolution and possible links to environmental changes that cause mass extinctions. The Parana-Etendeka continental flood basalts correspond to a voluminous and purportedly short magmatic event that erupted during the Early Cretaceous in southwestern Gondwana, predating its breakup. During this event, large amounts of mafic and felsic lavas and associated products (volcaniclastic rocks, dykes, sills and intrusive complexes) were formed. A compilation of the existing published Ar-40/Ar-39 step-heating (n = 378) and U/Pb (n = 32) ages, followed by the recalculation and filtering of the Ar-40/Ar-39 step-heating data, places the initial eruptive stages at 135.0 +/- 0.6 Ma, with the extrusion of the Tafelkop low-Ti mafic magmas. Volcanic activity peaked at 134.4 +/- 0.1 Ma with the ongoing emplacement of low-Ti magmas and with the onset of high-Ti mafic and silicic volcanism in the north, with major events lasting until 133.2 +/- 0.3 Ma and eruptions possibly ceasing at 132.0 +/- 0.2 Ma. Igneous activity, mostly in the form of dykes, apparently persisted for an additional 10 million years after the breakup of Gondwana and the subsequent initial drifting stages of the South Atlantic basin. The compiled and recalculated results confirm the brevity (1.6-3.0 m.y.) of the main phase of the Parana-Etendeka volcanism. They also suggest a possible temporal link between the Parana-Etendeka magmatism and the Weissert event delta C-13 excursion.