THE VINDHYAN ENIGMA REVISITED

The age of the Vindhyan Supergroup in central India has long been controversial. Geochronological dating now strongly favours a Palaeoproterozoic age for at least the Lower Vindhyan, but the controversy has been kept alive through reports of fossils of Neoproterozoic and Cambrian aspect from the sequence. We test the alternative hypotheses through an integrated palaeontological–geochronological investigation of key profiles. The occurrence of Lower Vindhyan fossils resembling forms known from Ediacaran–Cambrian rocks is confirmed: Annulated tubes, calcified cyanobacteria (Renalcis, Girvanella), embryo-like spheroidal fossils with polygonal surface structure, as well as “quilted pneus” similar to those found in Ediacaran deposits. None of these can be conclusively identified with biostratigraphically indicative taxa of Ediacaran–Cambrian age, however. In view of the strong geochronological evidence for a Palaeoproterozoic age of the Lower Vindhyan we need to consider the mounting indications that the Palaeoproterozoic biota was more diversified than is generally assumed.