Regional correlation of mudrock-siliciclastic units is challenging, largely owing to the apparent featurelessness of fine-grained intervals. This difficulty is multiplied when subsurface correlation is necessary for paleogeographic reconstruction. In this study, faunalmarker tracing and limestone-pattern matching have permitted subsurface correlation of the Alexandria submember of the Kope Formation (Edenian Stage, Upper Ordovician) over a 193-km transect in southwest Ohio. The faunal markers are thin (Ͻ10 cm), widespread deposits of skeletal debris exhibiting faunal associations, degrees of preservation, or both, that distinguish them from other fossil deposits in host mudrocks. Subsurface correlations corroborate interpretations of southwest Ohio paleogeography and demonstrate the usefulness of techniques presented here. Geographic trends in the data indicate that the average seafloor slope over much of the Cincinnati region was near zero. Evidence also indicates a northwestdipping paleoslope approximately normal to the study transect; this is likely a transition from the Kope environment into the Sebree Trough, a narrow basin with poorly understood morphology. A change from limestone-rich to limestone-poor facies, accompanied by replacement of oxic by dysoxic fauna, takes place over a maximum distance of 40 km between two localities along the transect. This represents improved constraint on the Kope-Sebree Trough boundary.

The idea of sending students and the general public on a walk through a scale model of the solar system in an attempt to instill an appreciation of the relative scales of the sizes of the objects compared to the immense distances between them is certainly not new. A good number of such models exist, including one on the National Mall in Washington, D.C., starting at the Smithsonian Air and Space museum.1 A pioneering model and inspiration for our own is on the campus of the University of Colorado in Boulder,2 and there are others.3 Those at science museums are often used by the general public and field-trip groups, while the ones on college campuses are also used by students of introductory astronomy.