Field Trip Photographs Sedimentology & Stratigraphy Course The College of Wooster Department of Geology Saturday, April 29, 2000 Trip to the Mississippian-Pennsylvanian Boundary in Jackson County, Ohio (Led by Professor Mark Wilson and Teaching Assistant Laura Clor)   For the schedule and travel directions, see our Field Trip Itinerary page.   Our first outcrop along US Highway 35 about three miles west of Jackson, Ohio. The Mississippian Logan Formation, composed primarily of coarse siltstones and very fine sandstones, is unconformably overlain by sandy conglomerates of the Pennsylvanian Sharon Conglomerate. The unconformity, highlighted here in red, is very irregular at this outcrop. Vertical relief along it is measured in meters. The Logan Formation alternates between thinly-laminated siltstones and sandstones and massive sandstones with some hummocky cross-bedding and worm burrow trace fossils. We interpret these beds as having formed on a shallow marine shelf with occasional storms. The Sharon Conglomerate was deposited by braided streams cutting into the consolidated shelf sediments.     A classic geology class pose: sitting on the side of a highway carefully drawing the stratigraphy and structures in a roadcut outcrop! This is at the first stop, with US Highway 35 in the background.     Here the Sed/Strat students are visible as colored dots at our Stop #2 outcrop (at the Apple City Motorcycle Club headquarters!) The dark unit at the base of the outcrop is the Logan Formation, with the Sharon Conglomerate forming the cliff above. Additional Pennsylvanian siliciclastic units are exposed above the Sharon.     Kirk Lapham, Tim Conklin and Aaron Shear explore the unconformity at Stop #2. this surface is much flatter than the previous stop, and the overlying Sharon Conglomerate is sandier, with the gravel confined to broad lenses typical of overloaded braided streams.     Jerome Hall climbs to the top of the Sharon Conglomerate to study the overlying claystones and thin sandstones. These upper units are very carbonaceous and apparently represent lagoons with occasional washover deposits of fine sand and silt. The most common fossils found in these units are plant fragments and Conichnus trace fossils, apparently representing burrowing sea anemones.     Upper view of Jerome Hall climbing the Sharon Conglomerate. It is along this ledge that we found a very nice Black Snake!     The Sed/Strat class arrayed along a mysterious concretion-bearing unit in unnamed Pennsylvanian rocks just north of Jackson County (Stop #3). The unit appears to be a sandstone formed by a crevasse splay event along a delta plain.   Please see the Hardground Web Project this class completed. We also have photographs from the April 2000 Field Trip. Return to the Sedimentology & Stratigraphy course page. Return to the Wooster Geology Courses on the Web menu page.