Marine barite (IMAGE) University of California - Santa Cruz Caption Marine barite extracted from deep-sea sediment cores, seen here in a scanning electron microscope image, provides a record of variations in ocean chemistry over geologic time. Credit Adina Paytan Usage Restrictions For use only with news coverage of this research 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.