California Rocks (IMAGE) University of California - Davis Caption Nitrogen-rich marine rocks from Northern California. Globally, rocks of sedimentary origin contain on average about 400 parts-per-million nitrogen. Previous assumptions maintained that all nitrogen came from the atmosphere. Credit Scott Morford/UC Davis Usage Restrictions Provide 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.