APPLICATION OF X-RAY COMPUTED TOMOGRAPHY REVEALS A (FOOL’S) GOLD MINE OF EXCEPTIONALLY PRESERVED FOSSILS IN THE SILICA SHALE (DEVONIAN) OF OHIO

The Silica Shale of northwestern Ohio contains a diverse assemblage of Middle Devonian fossils, many of which are pyritized. Body fossils have been collected from this unit for more than a century, and large collections of shelly taxa exist in museums, in universities, and privately. Study of a varied array of samples from the Silica Shale using X-ray Computed Tomography (XCT) reveals that internal soft tissues of shelly taxa are commonly replicated by pyrite. In addition, large numbers of pyritized trace fossils have been imaged in some layers. XCT scanning reveals the Silica Shale to be a remarkably rich Konservat-lagerstätte. So far, this nondestructive method has allowed visualization of the internal soft tissues of trilobites, brachiopods, and corals. Imaging the nonbiomineralized anatomy of shelly organisms, together with traces, provides new perspectives on the paleobiology and taphonomy of Silica Formation taxa, and provides new information about the bioturbation of bottom muds. Pyrite replication evidently began quickly after death. Approximately half of enrolled trilobites (Phacops) have preserved guts, whereas outstretched trilobites rarely show remains of the digestive system, leading to the inference that enrolled specimens were corpses, whereas most outstretched trilobites were probably molts. Most brachiopods (including Mucrospirifer, Paraspirifer, and Pseudoatrypa) have preserved brachidia, and a few have pyritized muscles and organs. Rugose corals (including Heliophyllum) have pyritized structures resembling mesenteries. The surprising results of XCT scanning on fossils from the Silica Formation suggests that other deposits containing pyritized fossils might be far richer in paleontological and sedimentational information than historically suspected.