Tree rings from a beam found in Por-Bajin (IMAGE) University of Groningen Caption A microscope image of the outermost tree rings in a beam from Por-Bajin. For the last ring, the tree only formed early wood (darker bands; lighter bands are late wood). The carbon-14 spike was discovered in the 3rd ring from the bark. Credit Petra Doeve Usage Restrictions With credit 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.