Abstract The linear Sequatchie anticline interrupts the continuity of the Appalachian Cumberland Plateau from east-Central Tennessee southward into Alabama to near the latitude of Birmingham. The anticline was breached by erosion during the late Tertiary, thereby producing Sequatchie Valley and revealing the details of its geologic structure—the anticline is thrust faulted on its northwest flank, and that thrust is now known to be part of a tectonic ramp that extends upward from the Lower Cambrian Rome Formation to flatten to the northwest into a higher detachment within the weak shale and coal beds in the Pennsylvanian deltaic sedimentary rocks. The same thrust emerges to the northwest as the Cumberland Plateau overthrust, and appears to be a mirror-image analog of the Pine Mountain fault located in the Plateau to the northeast. The purpose of this one-day field trip is to (1) provide an introduction to the Sequatchie Valley structure and the Mississippian-Pennsylvanian strata that form the crest and limbs of the anticline, and (2) gain some insight into the evolution of the topography in the southern Cumberland Plateau as the valley was exhumed during the late Tertiary. The first field trip stop is along Tennessee State Route (SR) 8 northwest of Dunlap to examine well-exposed rocks and structures along the upper detachment where it propagates along coal and shale beds in the Pennsylvanian section. The second field trip stop is up the southeast flank of the anticline along Tennessee SR-111 east of Dunlap to review the nearly continuous exposure of the Paleozoic section from the Devonian-Mississippian Chattanooga Shale to the top of the Mississippian.

Abstract The Pennsylvanian section on the southern Cumberland Plateau in the Sewanee and Tracy City area is composed of the Gizzard Group (Raccoon Mountain Formation, Warren Point Sandstone, and Signal Point Shale) and the lower portion of the Crab Orchard Mountains Group (Sewanee Conglomerate and Whitwell Shale). The hydrogeologic setting of the area controlled the founding and development of the town of Sewanee and University of the South. Water use initially relied upon a system of perennial springs, soil seeps, shallow wells, and a failed method of dam construction. Later, reservoirs with earthen dams across first-order drainages set the stage for growth of the community. Deformation associated with the Alleghanian Cumberland overthrust on the University Domain (more than 10,000 acres owned by the university) is subtle and confined to Bon Air coals in the Raccoon Mountain Formation, but a well-developed system of thrusts and folds in nearby Fiery Gizzard documents a consistent northwest tectonic transport direction. Deformation ranges from centimeter scale in Raccoon Mountain Formation mudstones to tens of meters of Warren Point Sandstone cut by northeast-striking thrusts. Deformation in Fiery Gizzard is locally related to two décollement surfaces above (intensely sheared Raccoon Mountain sandstone) and below (sheared Raccoon Mountain mudstones and coals) Sycamore Falls. Fourteen kilometers to the southeast, these overthrust structures are thought to connect to the Sequatchie thrust.

Abstract The E5 transect extends southeastward from the Cumberland Plateau across the Appalachian orogen, the Atlantic Coastal Plain, Continental Shelf and Slope, and the Blake Plateau Basin; it is a transect through the Precambrian-early Paleozoic and Mesozoic-Tertiary continental margins of North America. The transect consists primarily of a 100-km-wide geologic strip map, a cross section, and supporting geophysical data. The cross section is based on surface geology, surface and subsurface data from Coastal Plain and offshore drill holes, shipboard and aeromagnetic data, and gravity and seismic reflection data, including the ADCOH and COCORP southern Appalachians lines. Elements of the map and cross section include: (1) the Appalachian foreland fold-thrust belt and western Blue Ridge Late Proterozoic-Paleozoic continental margin; (2) the eastern Blue Ridge-Chauga belt-Inner Piedmont oceanic-continental fragment terrane; (3) the volcanicplutonic Carolina terrane containing the middle to late Paleozoic high-grade Kiokee belt; and (4) a major geophysical ly defined terrane beneath the Coastal Plain. Three Paleozoic sutures may be present along the section line: the Hayesville thrust, the Inner Piedmont-Carolina terrane boundary (Taconic or Acadian suture?), and an eastern boundary of the Carolina terrane (Alleghanian? suture) in the subsurface beneath the Coastal Plain. The modern continental margin consists of the terrestrial clastics-filled Triassic-Jurassic basins and offshore marine Jurassic- Cretaceous clastic-carbonate bank succession overlain by younger Cretaceous and Tertiary sediments. Above the Late Cretaceous onshore unconformity lie Cenozoic sediments that represent seaward prograding of the shelf-slope, truncated by Miocene to recent wave abrasion and currents.

Abstract DNAG Transect E-5. Part of GSA's DNAG Continent-Ocean Transect Series, this transect contains all or most of the following: free-air gravity and magnetic anomaly profiles, heat flow measurements, geologic cross section with no vertical exaggeration, multi-channel seismic reflection profiles, tectonic kindred cross section with vertical exaggeration, geologic map, stratigraphic diagram, and an index map. All transects are on a scale of 1:500,000.

Fault rocks can be studied by charting how undeformed rocks near a fault transform into mylonitic or cataclastic tectonites, or by examining rock masses at different points along a fault to determine how changes in temperature, pressure, etc. affected the fault’s history. Both approaches have merit in thrust belts because thrust faults form under a range of conditions and may evolve along several different paths. Using the first approach, we distinguish two fault zone types analogous to Means’ (1984) two types of shear zones: Type I fault zones grow in thickness as movement on the fault increases; Type II fault zones initiate as zones of localized deformation, and deformation becomes further localized as displacement increases. Both Type I and Type II fault zones occur in the Appalachian fold-and-thrust belt. The second approach shows that fault rocks from the thrust zone beneath the southern Appalachian Blue Ridge and that beneath the Bay of Islands ophiolite evolved in similar ways, despite differences in rock types and local structural history. Three conclusions emerge from our survey of fault rocks from thrust faults: (1) rocks from both external and internal thrust zones may deform by fracturing or by plastic flow, and may alternate between those modes as local physical conditions change; (2) fault zones with large displacement nearly always weaken with continued displacement; (3) fluid phases are critically important to the softening processes, which accommodate large displacements in both external and internal thrust zones.

The stratigraphy of the Pennington Formation (Upper Mississippian) and the Gizzard (Mississippian and Pennsylvanian) and Crab Orchard Mountains Groups (Lower Pennsylvanian) reflects a suite of littoral sedimentary environments which prograded west and south into the southern Cumberland Plateau of Tennessee from the central Appalachians. Because rock-stratigraphic nomenclature in southern Tennessee evolved separately from nomenclature in Kentucky and Virginia, and because stratigraphic relations are complex, different classification schemes and formational boundaries are used in different places for similar sequences of strata. In the southern Cumberland Plateau of Tennessee, distribution of Gizzard depositional environments seems to be in part tectonically controlled, with barrier sandstones along the more stable shelf and with lagoon and marsh deposits in adjacent sedimentary basins.