Trace fossils of the Whitewater, Saluda and Liberty Formations in southeastern Indiana (section authored by Evan Berliner)

Trace fossils, or ichnofossils, are structures left in the sediment from the life activities of an organism. Trackways, trails, borings and burrows are all example of trace fossils. Ichnofossils are important because they can provide indications for interpreting sedimentary environments, paleobathymetry, diagenetic history and most importantly the behavior of organisms. In some cases, fossilized behavior is the only evidence for ancient life. Trace fossils do have limitations because many organisms create various traces which can be hard to interpret. Their advantage over body fossils is invaluable. Environmental conditions may not be suitable for body preservation, diagenesis might ruin a body fossil but the paleontologist can always be certain the trace has not be transported or moved after being made by the organism.

Evan Berliner, Senior Geology major at The College of Wooster. Evan is from Pittsburgh, Pennsylvania.

Seafloor dissolution of a bivalve shell showing remaining borings on a bioimmuring trepostome bryozoan. A second trepostome bryozoan has started growth on the underside of the first. (Complete description below.)

Worm burrow in convex hyporelief found in the Liberty Formation of the Richmondian Stage (Ordovician).

In the Ordovician rocks of the Cincinnati area, various ichnofossils can be found. Trace fossils of branching tunnels, U-shaped tubes, elongate borings and cylindrical borings are most common. The Upper Ordovician fossiliferous limestones and claystones of the Richmondian stage in the Cincinnati area are in the Whitewater, Saluda and Liberty Formations. Some examples of typical ichnofossils include: Chondrites Diplocraterion Petroxestes Rusophycus Trypanites Diplichnites Planolites Palaeophycus Skolithis Zoophycos bryozoan Ropalonaria borings

Larger worm burrow in convex hyporelief of the same Liberty Formation.

The Upper Ordovician limestones and claystones of the Whitewater, Saluda and Liberty Formations yield marine ichnofossils created by marine filter-feeding worms, bryozoan borings, clam borings, and trilobites. In Figure 1, there are visible elongate borings in a trepostome bryozoan. Originally an encrusting trepostome began growth on a bivalve shell. A filter-feeding marine worm created borings between the bivalve shell and the bryozoan. Termed seafloor dissolution, the aragonite bivalve dissolved leaving the calcite bryozoan and giving a cross-sectional view of the borings created by the worm. After dissolution of the bivalve shell another bryozoan began growth on the underside of the original bryozoan. The filter-feeding bryozoans and ichnofossils indicate nutrient-rich, agitated water with little sediment in suspension.