Look at the data around the late Cretaceous Deccan Traps eruptions. It's pretty clear that large scale volcanic activity is the real culprit, just as it's been

Look at the data around the late Cretaceous Deccan Traps eruptions. It's pretty clear that large scale volcanic activity is the real culprit, just as it's been with nearly every mass extinction event. The impact event had a big effect too but the end was already written before the cosmic gun went off. There's also emerging evidence that dinosaurs survived in pockets for a few hundred thousand years after the impact. Most of this comes out of New Mexico and is based on radiometric sequences that have yet to be accepted on a wide scale, but it is there.