The prevailing hypothesis for the extinction of the dinosaurs was the impact of an asteroid at Chicxulub in Mexico at the end of the Cretaceous period which caused world wide fires.
The evidence for the fires was a global layer of soot in rocks of that age, but no charcoal have ever been found in this layer. Gas chromatography was used to determine the source of the soot, now suggested to be oil and/or gas rather than vegetation. More here from Nature:
http://www.nature.com/news/2009/0902....2009.112.html
Al.