Hell Creek Formation (IMAGE) University of California - Berkeley Caption Team leader Paul Renne collecting a volcanic ash sample from a coal bed within a few centimeters of the dinosaur extinction horizon. Credit Courtney Sprain Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.