These initially homogeneous sediments form an excellent setting for studying long-term organic matter remineralization processes to establish the extent and possible selectivity of oxic vs. anoxic degradation of organic matter in a natural environment. The organic fraction in the lower part of organic-rich turbidites has remained virtually unchanged for periods as long as 14 m.y. under suboxic to anoxic conditions. In contrast, dramatic changes have occurred during the post-depositional oxidation of sediments in the tops of the same turbidites by oxygen. Furthermore, a decrease is observed in the total carbonate content, which is related in part to the oxidation of organic matter and S-compounds. Major and minor element compositions of sediments do not seem to be affected by the oxidation process if they are normalized to Al.
Sulfur is the main exception.