The post-Paleozoic chronology and mechanism of 13 C depletion in primary marine organic matter Popp, B. N. ; Takigiku, R. ; Hayes, J. M. ; Louda, J. W. ; Baker, E. W. Abstract Publication: American Journal of Science Pub Date: April 1989 DOI: 10.2475/ajs.289.4.436 Bibcode: 1989AmJS..289..436P