Mercato Limestone (IMAGE) Duke University Caption Italian limestone collected from the Mercato San Severino section in southern Italy contains molecular traces of ancient oceanic chemistry. An analysis of these rocks helps explain how early Jurrasic volcanism lead to de-oxygenation of the ocean and mass extinctions. Credit Mariano Remírez, George Mason University Usage Restrictions none License Original 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.