Paleoenvironment of New Trace Fossils from the Eocene Mission Valley Formation, California

Two new ichnogenera and ichnospecies, Diopatrichnus roederensis, the fossil shell-lined tube of the onuphid polychaete Diopatra, and Anconichnus horizontalis, a fossil burrow of unknown origin, are named and described from their occurrence in the middle Eocene Mission Valley Formation in San Diego, California. Distribution of living species of associated genera of foraminifers, ostracodes, and molluscs, together with the presence of carbonized algal fragments suggest deposition in inner shelf depths, 100 m or less and possibly less than a few tens of meters. Moderate current action is suggested by shell distribution and by the presence of Diopatra.