A NEW SILURIAN (LUDLOW, GORSTIAN) TRILOBITE FAUNA FROM PIPE CREEK JUNIOR QUARRY, SWAYZEE, GRANT COUNTY, INDIANA

Pipe Creek Junior is a quarry in a rare limestone Silurian reef in Grant County, Indiana. It features spectacular exposures of steeply dipping Silurian distal reef flank beds. Most Silurian rocks in the region were hydrothermally dolomitized which destroyed primary sedimentary fabrics and fine fossil details. Pipe Creek Junior was largely unaffected by these processes, so most of the original fabrics, cements and fossil textures were preserved- accomodating study of Silurian reef depositional systems and biota.

A limited group of distal flank beds exhibits a highly diverse fauna of trilobites that differs from that seen in most Midwestern reefs. , and one of us (Havens) has been collecting trilobites from the quarry since 1992 and amassed a collection of over 900 trilobite fossils. A partial list of taxa includes Styginidae (including a bumastine and a scutelluid), Harpetidae (including Scotoharpes?), Lichidae (Genera Dicranopeltis and Hemiarges (?)), Odontipleuridae (including Dudleyaspis, Ceratocephala), Calymenidae (Genus Calymene), Cheiruridae (including Cheirurus?, Deiphon, Sphaerexochus, Youngia) Encrinuridae (Genus Struzia), Phacopiodae, and Proetidae. There appears to be several undescribed genera and species in this fauna which will be described at a future date.

Most of the trilobites were collected from the proximal reef flank beds, and many of these were also found in a lateral bioherm. Phacopids are exceptional in being found farther from the reef core, always in very coarse grained rocks. One unusual Sphaerexochus pygidium came from distal flank beds.

We are in the process of photographing and describing this large and unique collection. The goal of this project will to describe and quantify a rare and poorly known highly diverse late Silurian trilobite fauna from the Midwest.