dinosaur die-off, chicken or egg

http://www.sciencedaily.com/releases/2005/08/050810130729.htm

There is an argument among some scientists about what caused the climate changes 65 million years ago that led to the extinction of the dinosaurs. Some believe it was due to an asteroid impact. Others blame it on massive volcanic action. Both have been shown to have occured at that time. It seems to me an obvious possibility that an asteroid impact could have triggered these massive lava flows, but I haven't seen this possibility discussed.