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 Exposures of Ordovician rocks of the Sauk megasequence in Missouri and northern Arkansas comprise Ibexian and lower Whiterockian carbonates with interspersed sandstones. Subjacent Cambrian strata are exposed in Missouri but confined to the subsurface in Arkansas. The Sauk-Tippecanoe boundary in this region is at the base of the St. Peter Sandstone. Ulrich and associates divided the Arkansas section into formations early in the 20th century, principally based on sparse collections of fossil invertebrates. In contrast, the distribution of invertebrate faunas and modern studies of conodonts will be emphasized throughout this chapter. Early workers considered many of the stratigraphic units to be separated by unconformities, but modern analysis calls into question the unconformable nature of some of their boundaries. The physical similarity of the several dolomites and sandstones, complex facies relations, and lack of continuous exposures make identification of individual formations difficult in isolated outcrops. The oldest formation that crops out in the region is the Jefferson City Dolomite, which may be present in outcrops along incised river valleys near the Missouri-Arkansas border. Rare fossil gastropods, bivalves, brachiopods, conodonts, and trilobites permit correlation of the Cotter through Powell Dolomites with Ibexian strata elsewhere in Laurentia. Conodonts in the Black Rock Limestone Member of the Smithville Formation and the upper part of the Powell Dolomite confirm regional relationships that have been suggested for these units; those of the Black Rock Limestone Member are consistent with deposition under more open marine conditions than existed when older and younger units were forming. Brachiopods and conodonts from the overlying Everton Formation assist in interpreting complex facies within that formation and its correlation to equivalent rocks elsewhere. The youngest cono-donts in the Everton Formation provide an age limit for the Sauk-Tippecanoe unconformity near the southern extremity of the great American carbonate bank. The correlation to coeval strata in the Ouachita Mountains of central Arkansas and in the Arbuckle Mountains of Oklahoma and to rocks penetrated in wells drilled in the Reelfoot rift basin has been improved greatly in recent years by integration of biostratigraphic data with lithologic information.

Abstract This trip crosses a wide-expanse of typical Valley and Ridge geology and topography before reaching the gentler structure of the Powell River anticline with its numerous zinc and lead occurrences. The largest of these, the New Prospect mine, is Stop 3. Here the mineralization occurs in Maynardville Limestone along fault and shear zones rather than in collapse breccias. Stop 4 will be at the famous Thorn Hill section where the roadcut for highway US-25E traverses strata from lower Cambrian to lower Mississippian in age. Selected sites will be examined. The remainder of this trip will cover the area northeast and southeast of the Mascot-Jefferson City district, concentrating on the post-Knox unconformity and its solution features. Stop 5, just south of Dandridge along Douglas Lake, provides a look at a quartz sand-filled depression in the erosion surface. At Stop 6, west of Dandridge at the Shady Grove area, two large, relic sinks filled with blocks of dolomite and chert will be seen. This karst development is believed related to the development of the large breccia bodies which are common to the upper Knox dolomite and which are ore hosts in the mineralized districts.

Parts of the central and southern Appalachian orogen appear to have evolved away from Proterozoic North America (Laurentia) and to have been accreted to it during the Paleozoic orogenies that collectively formed the orogen. Identifying each tectonostratigraphic terrane is a necessary step in understanding the evolution of the orogen. The terranes in the central and southern Appalachians are delineated, interpreted, and classified with varying degrees of confidence as: (1) Laurentian native terranes, (2) internal continental terranes of the Appalachian orogen, (3) disrupted terranes, (4) possible oceanic crustal remnants, (5) volcanic-arc terranes, (6) a continental terrane of Gondwanaland affinity, and (7) metamorphic complexes of undetermined affinity. The Laurentian native terranes consist of external massifs of Laurentian basement (Grenvillian and older), their rift- and shelf-facies cover rocks, and slope-rise prism deposits. External massifs are present in the Blue Ridge tectonic province, Reading Prong, and Honey Brook Upland. Rocks of the Talladega block are stratigraphically tied to Laurentia and, with the possible exception of the Hillabee greenstone, are also considered native. Offshore, deep-water, post-rift deposits of the Hamburg and Westminster terranes have no direct stratigraphic ties to Laurentia and are considered discrete native (not suspect) terranes. The internal continental terranes of the Appalachian orogen are isolated massifs of Middle Proterozoic (Grenvillian) continental basement and their cover sequences that occur within the metamorphic core of the orogen. These terranes, the Baltimore, Sauratown, and Pine Mountain terranes, could be either structurally isolated outliers of Laurentia or microcontinental fragments of Laurentian crust displaced by rifting or transcurrent faulting and later reassembled. Disrupted terranes in the central and southern Appalachians contain mélange complexes as well as more coherent terrane fragments (volcanic, ophiolitic, or continental) intermingled with the mélange complexes. Those identified include the Jefferson, Potomac, Smith River, Inner Piedmont, Falls Lake, Juliette, and Sussex terranes. The Bel Air–Rising Sun terrane (Baltimore Complex) in Maryland and Pennsylvania is the only terrane named separately as a possible oceanic crustal remnant. Similar mafic and ultramafic complexes are present in all of the disrupted terranes, but are too small to consider as separate terranes. Volcanic-arc terranes include the Chopawamsic, Carolina, Spring Hope, Roanoke Rapids, and Charleston terranes. The only terrane recognized as a continental terrane of Gondwanaland affinity is the Suwannee terrane, which contains rocks believed to correlate with those now exposed in west Africa. Metamorphic complexes of undetermined affinity are terranes that could not be clearly classified on the basis of available data. These include the Milton, Gaffney, Uchee, Crabtree, Goochland, Wilmington, and Hatteras terranes. The Penobscottian, Taconian, Acadian, and Alleghanian Paleozoic compressional events collectively assembled the various terranes into what is now the Appalachian orogen. Only the central and southern parts of the U.S. Appalachians are considered here. The Penobscottian orogeny, about 550 to 490 Ma, amalgamated the Potomac, the Chopawamsic, probably the Bel Air–Rising Sun, and possibly other exotic terranes at some unknown distance from Laurentia. This was followed by the Taconian orogeny, about 470 to 440 Ma, which accreted the previously amalgamated terranes and probably other terranes such as the Carolina terrane to Laurentia. The younger age limit for the Taconian event is partly constrained by Middle and Late Ordovician faunal assemblages in successor basin deposits of the Arvonia Slate and Quantico Formation. The significance of the Acadian orogeny, dated about 400 to 380 Ma in New England, is unclear in the central and southern Appalachians. In the Talladega block of Alabama and Georgia, an Early to Middle Devonian dynamothermal event is firmly bracketed between Early Devonian fossils and K-Ar ages that indicate a thermal peak no later than Middle Devonian time. A regional tectonothermal event and faulting of approximately this age are also suggested by isotopic studies in terranes to the east. The late Paleozoic (Alleghanian) continental collision between Laurentia and Gondwanaland, which formed the supercontinent Pangea, marks the final stage of accretionary history in the Appalachian-Caledonide orogen. Effects evident in the central and southern Appalachian region include: (1) the accretion of the Suwannee terrane and perhaps the Charleston terrane to what is now North America, (2) slicing and shifting of terranes along dextral strike-slip faults, particularly in the eastern Piedmont, (3) westward transport of native and previously accreted terranes in the western Piedmont and Blue Ridge as part of a composite crystalline thrust sheet, (4) deposition of clastic wedges in the Appalachian foreland, and (5) imbricate thrusting and folding of the resultant strata in the Valley and Ridge Province.