TRACE FOSSIL MORPHOLOGIES IN THE NEW ALBANY SHALE OF SOUTHERN INDIANA HELP TO DERIVE SEDIMENT HISTORY

Differing morphologies of trace fossils in the Selmier and Camp Run Members of the Late Devonian New Albany Shale in southern Indiana indicate differences in the water content of sea floor muds and the time frame of oxygenation at time of bioturbation. Both the Selmier and Camp Run Members are composed of greenish gray to olive-gray shale interbedded with brownish black shale. Trace fossils in the Selmier Member are most prevalent in the greenish gray to olive-gray shale where they completely obliterate bedding with shallow tiering of smaller sized burrows in the brownish black shale. The Selmier Member has relatively few trace fossils that are identifiable to the genera level, but more commonly seen are mantle and swirl morphologies that indicate organisms moved through soupy sediments with a water content of ~70%. Trace fossils in the Camp Run Member are also most prevalent in the greenish gray to olive-gray shale where they obliterate bedding with deeper tiering of large Zoophycus and Chondrites burrows into the brownish black shale. Zoophycus burrows are often crosscutting the obliterated bedding, and spreite are seen in Zoophycus burrows when observed closely. The presence of discrete traces, deeper tiering, and the recognition of spreiten suggest that the shale beds in the Camp Run Member experienced bioturbation for a longer time interval after deposition when compared with the Selmier Member. Whether this represents greater and longer oxygenation levels relative to the Selmier Member, or whether it points to distinct differences in the sediment accumulation dynamics between the two members is the focus of ongoing investigations.