At http://phys.org/print337590873.html … a group of geologists from MIT and further afield claim there was a major volcanic eruption just prior to the asteroid strike that produced the Chicxulub crater in the Yucatan. Previously, the volcanism has been dated post the asteroid strike – so is this a bit of strained back to front thinking?
They say they have precisely dated the rocks from the Deccan Traps in India and declare the truthfulness in the idea that a large volcanic eruption began as early as 250,000 years prior to the asteroid strike – in spite of the fact that the Deccan Traps occur on the opposite side of the world to Chicxulub and more likely erupted in response to the asteroid rather than before or after it. The problem is of course centred around dating methodology – and the faith of the scientists in the ratio of uranium to lead isotopes produced from zircon grains inside the rocks of the Deccan Traps. The paper is in the journal Science but the new hypothesis is now that the volcanism began 250,000 years prior to the asteroid strike and 500,000 years after it – which says it all really.