authigenic

You have access
Carbon isotopes in clastic rocks and the Neoproterozoic carbon cycle
Donald E. Canfield, Andrew H. Knoll, Simon W. Poulton, Guy M. Narbonne and Gregory R. Dunning

American Journal of Science February 2020, 320 (2) 97-124; DOI: https://doi.org/10.2475/02.2020.01