Carbonate Rock (IMAGE) University of California - Riverside Caption This is a carbonate rock in Zimbabwe used to trace sulfate levels in the Earth's early oceans. Credit Lyons Lab, UC Riverside 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.