Drill Core of Iron Formations (IMAGE) University of California - Riverside Caption Image shows an example of drill core of the chemical sediments called iron formations that the UCR-based team used to track marine phosphorus concentrations. The core is from the approximately 2.2 billion-year-old Hotazel Formation from South Africa. 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.