We report a newly determined age ($1647\pm 18$ Ma) for a rare magmatic zircon extracted from a very fine-grained felsic ash bed in the type area of the Porcellanite Formation, Vindhyan Supergroup, India, and chemical compositions of two samples from this ash bed. The new results, in the context of published literature, (1) firmly establish the age of the Porcellanite Formation between ∼1640 and 1630 Ma and (2) suggest that Plinian eruptions took place from isolated vents along a 300-km crustal fracture.