40Ar-39Ar ages of Bombay trachytes: evidence for a Palaeocene phase of Deccan volcanism

We present 40Ar-39Ar ages of 60.4 +/- 0.6 Ma and 61.8 +/- 0.6 Ma (2 sigma) for Deccan Trap trachytes from Manori and Saki Naka, Bombay, situated in the tectonized Panvel flexure zone along the western Indian rifted continental margin. These ages provide clear evidence that (i) these trachytes are of Palaeocene age and therefore substantially younger than the lower part of the main flood basalt sequence exposed in the Western Ghats, which precedes the K-T Boundary in age and (ii) the formation of the Panvel flexure along the west coast must have been subsequent to similar to 60 Ma. Considering early alkaline Deccan rocks previously dated at similar to 68.5 Ma, the total duration of Deccan volcanism was at least similar to8 MY.