THE JACK MOUNTAIN THRUST SYSTEM AND EOCENE MAGMATISM, HIGHLAND COUNTY, VIRGINIA: LINKING STATEMAP MAPPING TO FIELD COURSE EDUCATION (Invited Presentation)

It has been an honor in my geological career to have worked with Rick Diecchio for 16 years during which we had a productive stint teaching field course. Rick instilled in me insights into integrating regional stratigraphic relationships with tectonic history in the southern Appalachian orogen and eastern Colorado Plateau. He also mentored me to be a thoughtful and effective educator after his years serving as a GMU faculty member, Chair, and Associate Dean. Our working relationship began in 2001 as instructors for the UNC System-Wide Field Course in NM and CO where we honed our field project goals, deliverables, and grading. Then, from 2007–2016, we developed and taught a UNCW–GMU Field Course linking a VA East Coast component (lots of trees!) and NM Out West component (see forever!) as many of our graduating seniors gain employment that includes East Coast field work.

The six-day East Coast project originated with Rick and Lee Avary, Ron McDowell, and Dave Matchen at the WV Geologic and Economic Survey as a study of the central Appalachian foreland basin across the macroscale Jack Mountain anticline in Highland County, VA. In a section of Ordovician Reedsville, Oswego, and Juniata Formations (Fms) and Silurian Tuscarora and Rose Hill Fms, Rick recognized that the Reedsville structurally overlies the Juniata across the informal “Jack Mountain thrust system,” an east-directed thrust on the west flank of the anticline. Mapping by UNCW-GMU students then identified three Tuscarora quartz arenite fins representing two additional east-directed thrusts placing the Juniata over Tuscarora Fms. Internally across the breached anticline hinge along Wooden Run, students located sets of mesoscale parasitic folds, locally developed axial planar pressure solution cleavage, fractures, and backthrusts (i.e., “Bloody thrust”). These structures may be a progressive sequence of local western flank: (1) backthrusting and folding, or (2) folding and backthrust development. Students also mapped Eocene biotite-sanidine porphyry rhyolite and aphyric basalt dikes, and a plug including olivine-titanaugite porphyry basalt and sedimentary clasts in basaltic andesite(?) matrix.

Due to Rick’s superb observational skills and geological experience, we turned a WV STATEMAP project into an excellent applied field experience for our students.