FOSSIL FIELD TRIP TO OHIO AND INDIANA
On Saturday, 20 November 2010, the geology club took a fossil collecting field trip to southwestern Ohio and southeastern Indiana. The first stop was Caesar Creek Lake State Park. The visitor center near the dam for the lake has several fossil displays of local Late Ordovician-aged fossils, including a large, complete Isotelus trilobite (Ohio's official state fossil), plus modern wildlife-related exhibits. A couple hour's worth of fossil collecting was done at the nearby Caesar Creek Lake’s emergency spillway, which has an extensive exposure of interbedded fossiliferous limestones and fossiliferous shales (Waynesville Formation, Liberty Formation, Whitewater Formation - all Upper Ordovician). Commonly seen fossils included brachiopods, bryozoans, nautiloids, clams, snails, and trilobite fragments.
Fossil collecting at Caesar Creek Lake's emergency spillway (northeastern Warren County, southwestern Ohio, USA). The walls & slopes of this exposure are interbedded limestone & shale, all richly fossiliferous. The beds that stick out are the limestones. The gray beds in-between are the shales. The most common type of fossil found here is brachiopod shells (lower right-hand corner) - this one is Rafinesquina ponderosa.
Fossiliferous limestone - this fossil plate is typical of the limestone interbeds exposed at Caesar Creek Lake's emergency spillway (northeastern Warren County, southwestern Ohio, USA). The shells are various species of brachiopods, dominated by the strophomenid brachiopod Rafinesquina ponderosa. This is from the upper Liberty Formation or lower Whitewater Formation (upper Cincinnatian Series, upper Upper Ordovician).
A large roadcut in southeastern Indiana was visited next - Southgate Hill along Rt. 1, north of St. Leon and south of the Whitewater River. The rocks there also included interbedded limestones and shales, all richly fossiliferous, and the same age as the rocks at Caesar Creek. The fossils seen at Caesar Creek were also seen at Southgate Hill. Unusual finds of the day included a small, but nice, lustrous pyrite crystal mass and the head of a rare local trilobite, Ceraurus milleranus.
Southgate Hill - this is part of a large roadcut in southeastern Indiana, USA. The rocks are interbedded fossiliferous limestones and shales. The slope in the center of this photo is the upper Waynesville Formation (Cincinnatian Series, upper Upper Ordovician).