UPPER ORDOVICIAN ROCKS IN THE VICINITY OF MAYSVILLE, KENTUCKY: A FIELD TEACHING LABORATORY FOR HISTORICAL GEOLOGY STUDENTS

The rocks in and around Maysville, Kentucky are known for their abundant, diverse, and well preserved fossils. During Late Ordovician time (about 450 million years ago), the region was covered by a shallow epicontinental sea that was teeming with marine invertebrates, such as bryozoans, brachiopods, trilobites, cephalopods, bivalves, gastropods, crinoids, corals, etc.

This geologic setting is a wonderful field laboratory for students of historical geology. For many years Marietta College and West Virginia University at Parkersburg, separately, have been escorting students to study the Upper Ordovician limestones and shales outcropping there. The students may be both geology majors and non-majors. Maysville, Kentucky is about a three hour drive from the Marietta-Parkersburg area and the students are typically transported in vans to the locality. The trip can be completed in one long day, but sometimes students and professors spend the night in a motel in the area and continue to study the outcrops and collect fossils the following day.

During Late Ordovician time the Taconic Orogeny forming the Taconic Mountains to the east of this area (due to plate tectonic activity) resulted in periodic episodes of clastic sedimentation with fine clay transported to this area to form muddy bottoms that would form shales alternating with times of low clastic input that would result in limestones. The resulting thick sequence of alternating fossiliferous limestones and shales (about 75 meters represented by the Kope, Fairview, and Grant Lake formations at the Ohio River suspension bridge locality on Kentucky Route 3071) impresses upon students the time span that would be necessary for these deposits to accumulate. Other principles and concepts of historical geology that may be discussed during these field trips include superposition, lateral continuity, fossil succession, index fossils, correlation, paleoecology, paleogeography, paleoenvironmental analysis, relative geologic time, and absolute geologic time. Primary sedimentary structures such as ripple marks and trace fossils are also common in these deposits. Some unique features that may be found in these rocks are shingled brachiopod shells deposited during severe storms and ball and pillow structures that may be related to regional earthquake activity.