COPROLITES FROM THE PIPE CREEK SINKHOLE (LATE NEOGENE, GRANT COUNTY, INDIANA)

The Pipe Creek Sinkhole (PCS: Pipe Creek Jr. Quarry, Irving Materials Inc., Swayzee, Grant County, Indiana) preserves a diverse assemblage of continental plant and animal fossils of latest Hemphillian (Mio-Pliocene) age. Screen-washing of in situ fossiliferous sediments in 2003 yielded two specimens (lab numbers PCC-1 and PCC-2) that are here identified as coprolites. The oblong masses are about 3 centimeters long, 2-2.5 cm in maximum width, and cylindrical to elliptical in shape. Quantitative electron microprobe maps of PCC-1 revealed that the coprolitic ground mass is dominated by high concentrations of phosphorus and calcium, with minor amounts of manganese and iron. Energy Dispersive X-ray spectroscopy of PCC-2 indicated similarly high contents of P (weight % 14-15; atomic % 10-11) and Ca (weight % 34-35, atomic % 19-20), and lesser amounts of F, Mn, and Fe. These analyses indicate that both specimens are predominantly composed of apatite, a composition consistent with their being coprolites of carnivorous animals. Internally PCC-1 includes numerous parallel linear voids which were once apparently occupied by mammal hairs, as well as a relatively large inclusion that is probably a tooth. PCC-2 is more amorphous internally. Potential producers of the PCS coprolites present in the skeletal fauna include peccaries, felids, ursids, and canids; scat from modern representatives of some of these groups nicely matches the size and shape of the PCS coprolites.