Post-K/PB younger 40Ar–39Ar ages of the Mandla lavas: Implications for the duration of the Deccan volcanism

Abstract

We present new age determinations, derived from 40Ar–39Ar incremental heating experiments, for basaltic lava flows from the Mandla lobe, located on the eastern margin of the main Deccan volcanic province, some ~1000km from the Western Ghats escarpment. The most reliable estimates of crystallization ages come from 5 plateau ages from plagioclase separates, from a stratigraphically controlled succession of 37 lava flows. We detect no statistically significant age difference from bottom to top (range 63–65Ma) and calculate a weighted mean age for the section at 64.21±0.33Ma. These lava flows are significantly younger than the majority of the main Deccan volcanic activity documented from the Western Ghats (67–65Ma). The new ages are consistent, however, with geochemical correlation of the Mandla lobe lavas with the uppermost succession (Poladpur–Ambenali–Mahabaleshwar Formations) of the SW Deccan, and indicate that this post K/PB youngest phase of flood basalt activity erupted over much of the province.