Manganese distribution in the carbonate fraction of shallow and deep marine lithofacies,Middle Ordovician,Eastern Tennessee

A marked increase in manganese content from shallow to deep marine lithofacies can be observed within the carbonate fraction of the Middle Ordovician sequence in eastern Tennessee. The distribution of manganese is controlled by: (1) the original aragonite and calcite mineralogy of shallow and deep marine environments, respectively; (2) preferential substitution of manganese for calcium in the rhombohedral structure of calcite; (3) anoxic depositional and diagenetic environments; and (4) possibly, volcanism.