Abstract The morning portion of this trip traverses mainly Lower Ordovician Knox Group strata and makes a close encounter with the Rocky Valley overthrust fault enroute to American Smelting and Refining Company’s (ASARCO) Young mine and mill complex ( Stop 3 ). The Young mine, located near the center of the Mascot-Jefferson City zinc district, is the largest of the operating mines. The ore occurs mainly in collapse breccias which will be observed during an underground tour led by ASARCO staff. Access may possibly be by way of the Beaver Creek shaft. The afternoon portion of this trip will cross a wide-expanse of typical Valley and Ridge geology and topography before reaching the gentle structure of the Powell River anticline with its numerous zinc and lead occurrences. The largest of these, the New Prospect mine, is Stop 4 . Here the mineralization occurs in Maynardville Limestone along fault and shear zones rather than in collapse breccias. On the return to Morristown the trip passes the well-known Thom Hill section where the roadcut for highway US-25E traverses well-exposed strata from lower Cambrian Rome Formation to lower Mississippian Grainger Formation. A short stop will be made at the top of Clinch Mountain to observe the wide expanse of the valley of East Tennessee that stretches all the way southeast to the Smoky Mountains. It also presents an opportunity to take a look at the Clinch Sandstone. The return to Morristown crosses several belts of mostly Lower Paleozoic formations as well as several arms of Cherokee Lake.

ABSTRACT The southern Appalachian western Blue Ridge preserves a Mesoproterozoic and mid-Paleozoic basement and Neoproterozoic to Ordovician rift-to-drift sequence that is metamorphosed up to sillimanite grade and dissected by northwest-directed thrust faults resulting from several Paleozoic orogenic events. Despite a number of persistent controversies regarding the age of some western Blue Ridge units, and the nature and extent of multiple Paleozoic deformational/metamorphic events, synthesis of several multidisciplinary data sets (detailed geologic mapping, geochronology and thermochronology, stable-isotope chemostratigraphy) suggests that the western Blue Ridge likely records the effects of two discrete orogenic events. The earlier Taconic (470–440 Ma) event involved a progression from open folding and emplacement of the Greenbrier–Rabbit Creek and Dunn Creek thrust sheets as a foreland fold-and-thrust to low-grade hinterland system (D 1A ), followed by deep burial (>31 km), pervasive folding of the earlier-formed fault surfaces, and widespread Barrovian metamorphism (D 1B ). Because this high-grade (D 1B ) metamorphic event is recorded in Ordovician Mineral Bluff Group turbidites, this unit must have been deposited prior to peak orogenesis, possibly as a foreland basin or wedge-top unit in front of and/or above the developing fold-and-thrust belt. The later Alleghanian (325–265 Ma) event involved widespread northwest-directed brittle thrusting and folding related to emplacement of the Great Smoky thrust sheet (D 2 ; hanging wall of the Blue Ridge– Piedmont thrust). Mid-Paleozoic 40 Ar/ 39 Ar muscovite ages from western Blue Ridge samples likely record post-Taconic cooling (hornblende and some muscovite 40 Ar/ 39 Ar ages) and/or Alleghanian thrust-related exhumation and cooling (ca. 325 Ma muscovite 40 Ar/ 39 Ar and 300–270 Ma zircon fission-track ages), as opposed to resulting from a discrete Neoacadian thermal-deformational event. The lack of evidence for a discrete Neoacadian event further implies that all deformation recorded in the Silurian–Mississippian(?) Maggies Mill–Citico Formation must be Alleghanian. We interpret this structurally isolated sequence to have been derived from the footwall of the Great Smoky fault as an orphan slice that was subsequently breached through the Great Smoky hanging wall along the out-of-sequence Maggies Mill thrust.