Image (IMAGE) Proceedings of the National Academy of Sciences Caption This is an image showing the 'Livello Bonarelli' interval of black shales in Furlo, Italy. The black shales are rich in organic matter, and indicate the enhanced preservation under anoxic conditions. This is the classic signature of an ocean anoxic event and these black shales are found around the world for this time period. Credit PNAS 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.