The Eocene (IMAGE) University of Tokyo Caption 34.5 million years ago, geological conditions boosted fish populations responsible for REY deposits. Credit © 2020 Ohta et al. Usage Restrictions © 2020 Ohta et al. 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.