Fieldwork (IMAGE) University College London Caption Sampling of Ordovician (450 million year old) sediments by first author Boriana Kalderon-Asael. Credit Ashleigh Hood Usage Restrictions Only in relation to this paper and 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.