'\rr~"'1 Gr \G,S· ·G-11- 7_00& Geological Society of America 2006 Southeastern Section Meeting Knoxville, Tennessee March 23-24,2006 Field Trip Guidebook Theodore C. Labotka and Robert D. Hatcher, Jr. Editors Hosted by Department of Earth and Planetary Sciences University of Tennessee and Tennessee Division of Geology State of Tennessee Department of Environment and Conservation Sponsors: Oak Ridge National Laboratory Tengasco Table of contents Pre-meeting field trips Geology of the Mesoproterozoic basement and younger cover rocks in the west half of 1 the Asheville 100,000 quadrangle, North Carolina and Tennessee-An updated look. Carl E. Merschat, Bart L. Cattanach, Mark W. Carter and Leonard S. Wiener Geologic excursion across part of the southern Appalachian foreland fold-thrust belt in 37 northeastern Tennessee. Peter j. Lemiszki, and Martin S. Kohl Post"meeting field trips The geology and natural history of Mount Le Conte, Great Smoky Mountains National 65 Park, Tennessee. Scott Southworth, Art Schultz, and Danielle Denenny The petrogenesis and tectonic implications of Blue Ridge mafic-ultramafic rocks: The 101 Buck Creek and Carroll Knob complexes, and rocks of the Addie-Willets region. Virginia Peterson,]e[frey Ryan, Steven Yurkovich,}onathan Burr, Sarah Kruse, and the 1997-2001 REU Program Participants Geotraverse: Geology of northeastern Tennessee and the Grandfather Mountain region. 129 Robert D. Hatcher,}r., Arthur j. Merschat and Loren A. Raymond Lower Pennsylvanian siliciclastics of the northern Cumberland Plateau: Depositional 185 environments and biogenic structures of the Fentress formation and Rockcastle Con­ glomerate. Molly Miller, Andrew Rindsberg, and Susan R,jackson iii Geology of the Mesoproterozoic Basement and Younger Cover Rocks in the West Half of the Asheville 100,000 quadrangle, North Carolina and Tennessee-An Updated Look 2 3 Carl E. Merschatl, Bart L. Cattanach!, Mark W. Carter , Leonard S.Wiener INorth Carolina Geological Survey, 2090 U.S. Highway 70, Swannanoa, NC 28778 2Virginia Division of Mineral Resources, P.O. Box 3667, charlottesville. VA 22903 3North Carolina Geological Survey retired, 99 Ballard Branch Road, Weaverville, NC 28787 Abstract Bedrock geology of all 7.S-minute quadrangles in the west half of the Asheville 1:100,Ooo-scale map has now been mapped in detail by the North Carolina Geological Survey and other mappers with financial assistance from the STATEMAP program. A preliminary map by the North Carolina Geological Survey is presented here as part of an ongoing compilation project. For this preliminary compilation map, Mesoproterozoic basement rocks are placed into five major units: four highly deformed metamorphic units and the relatively undeformed Max Patch Granite. Contacts between the four metamorphic units are still uncertain but may be either faults, intrusive, or gradual changes of dominant rock type. A newly dated Neoacadian mylonitic shear zone separates Max Patch Granite from the highly deformed metamorphic basement rocks. To the southeast, basement rocks are in fault contact with the Ashe metamorphic suite along the Holland Mountain-Chattahoochee fault. To the northwest, Ocoee Su­ pergroup sedimentary rocks are separated from the basement along unconformities and Paleozoic fault zones. Paleozoic Barrovian metamorphic overprinting intensified from the northwest to southeast but is not observed in all areas of the basement. Granulite-facies rocks are present in localized bodies of the metamorphic basement units and likely preserve Grenvillian foliations. Introduction this paper we outline the map units, their currently known ages, and our present thinking as to their struc­ This paper and field trip focus on the history and rela­ tura] and metamorphic history. tionships of the igneous-metamorphic basement rocks Various map units distingUished during detailed in the sixteen 7.S minute quadrangles that constitute mapping of each individual 1:24,OOO-scale quadrangle the west half of the Asheville 1:100,OOO-scale geologic are possibly equivalent but may have different names map (Fig. 1). The crystalline basement in this area of on different maps. At this stage in the compilation of western North Carolina comprises part of the Mesopro­ the lOO,OoO-scale map, formal names for the basement terozoic metamorphic core of the southern Appalachian map units are not used except for the Max Patch Gran­ Mountains. Geologically, this metamorphic basement ite and Bakersville Metagabbro. We instead use informal core separates the Neoproterozoic Ashe metamorphic names taken from the major rock types that character­ suite-Tallulah Falls Formation to the east from Neopro­ ize each map unit. All of the many units mapped in the terozoic rocks of the Ocoee Supergroup and stra­ 7.5 minute quadrangles are listed in Figure 1 and are tigraphically overlying early Paleozoic sedimentary appropriately grouped into the composite units used in units to the west (Fig. 1). Each of the quadrangles that the 1:100,OOO-scale Asheville compilation. make up the west half of the Asheville sheet has now been mapped in detail (Table 1). This mapping, done at Historical background a 1 :24,000 scale, proVides data that add to, confirm, or modify conclusions of preceding geologists. Our Examining and investigating the rocks in an area to 1:100,000 compilation map is another step in the ongo­ determine their mineral composition, economic value, ing effort to decipher the region's geologic history. In stratigraphy. structure, and ultimately a synthesis of 2006 Southeastern Section meeting, Geological Society of America, field trip 1 2.""] Merschat et al. ,, 5 MILES TN ,-, 'HH TN , 10 KILOMETERS HHHAB N ~ NC ~.,- " I\ 'NC 35".10' 81 0 . Waynesville Fault Contact Lithostratigraphic Contact Figure 1. Preliminary compilation of the western portion of the Asheville 1:100,000 scale geologic map (west half shown by yellow box). Labeled boxes correspond to field trip stop locations. Original digital cartography by Mark W Carter. the region's geologic history is, of course, the task and etc." However, for most of the century little systematic goal of geologists. in western North Carolina the earli- attention was paid to the region's "country rock" with est formal geologic observations, made during the 19th most effort being devoted to discovering and promoting century, revealed that bedrock in the region was domi- the area's mineral wealth, especially iron ore, gems, nated by a great body of ancient-looking rocks. The first copper, mica, barite, and other commodities. It was not published state geologic map (Olmstead, 1825) used until near the end of the 19th century that a systematic Abraham Werner's Neptunist's classification system and and comprehensive program of mapping was conceived labeled these as "Granite-gneiss, Mica-slate, Argyllite, and begun. This program, undertaken by the u.s. Geo- Geology of the Mesoproterozoic Basemento 3 SEDIMENTARY SEQUENCES ACCESSORY UNITS PaInt Rock Hot Springs WhIte Rock Sams Gap Bald Creek o Ocoee Superg'oopJCambrlan Metasediments D Sericilicmylooile 8ea~. O.N .• (I %6) Fe'1luson. H.W. and Jewell. W.B .. (1951) Cl Brevard Fau~ Zo~e rocks D BaI<ersllilie Melagabbm Carter, M.W. (2001) MetSChal. C.E. and MelSdJal. C.E . and ~ersc"al. C.E .. (2000 Oriel. S.S .. (1950) all"" • • (2001) 01""15. (2000) Merschal, C.E. llI1d D Inne, Piedrnot1l rocks D Hornbleode-bearing melag,anile Caltanach (2004) STATE MAP STATE MAP STATEMAP STATEMAP STATEMAP D Ashe Melamorphlc Suile/Talullah Falls Formalion D Rocks 01 Unce~ain Affinity Lemon Gap Spring Creek Marshall Mars Hili Barnardsville IGNEOUS AND METAMORPHIC BASEMENT ROCKS BioMe Q'8/llIoI<I Gneiss MiU Palch G/ar>he and equlvalenls D D MelSCh.l. C.E. C. ~an och. 8.l. and Pelersoo. V. (2002} ~ersch.1. C.E . (1977 Merscl>al. C E • (1993 and othel'S . (2002) oll>ers. (2005) 8erquisl. P.J. (2003) D P,olorr>ylonruc Gran~oid Gnel$> Mered ulltamafic rock CJ layered Siclila Granitic Gnelss Amphiborote STATE MAP STATE MAP STATEMAl' STATEMAP Fines Creek Sandymush Leicester Weaverville Craggy . Mlgma~tic Biotile·Homble!1de Gneiss o Granul~e gnei$! Pinnacle Carter. M.W. aod Merschal. C E. and Mer..:hill, C. E. and 8urr. J.L. (2002) Wiener. LS .. (1999) Wione(. LS .. (1988) C.nanDch (2005) STATEMAP STATEMAP STATEMAP Clyde Canton Enka Asheville Oteen Figure 1, continued. Map explanation, above. M.,senet, C.E. aM Mersch.1. C.E. and Burr. J.L .. (2000) Miflc,. J.w. lind Nels.on. 0.0.. (1912) Index, right. Wl&r>e(.l.S .. (1992) Wi."er. LS. (1988) Fryer. K.H .. (2004) CaKanach. 8.L Md Merschal. C.E. (2005) S TATE MAP STATEMAP STATEMAP STATEMAP logical Survey, was aimed at producing a geologic atlas change in terminology from Carolina Gneiss and Roan of the United States. In the Appalachians a remarkable Gneiss to the lithologic terms mica gneiss and horn­ series of folios was ultimately published that covered blende gneiss shows that Keith's concept and wide­ ground from Alabama to New England. The area of the spread usage of the Carolina Gneiss and Roan Gneiss as west half of the present-day Asheville 100,Ooo-scale stratigraphic units was no longer fully accepted. map is the same as that of folio 116, the Asheville Folio, In 1971, the Knoxville 1:250,000-scale geologic map by Arthur Keith (1904). This important and impressive (Hadley and Nelson, 1971) was published. The Knoxville pioneer work presented abundant observations and quadrangle presented a significant revision of Keith's field descriptions, much of which we today can simply work, especially his stratigraphie interpretations, and ac~nowledge and reconfirm. As a result of his mapping, provided the framework for reinterpreting the area's Keith concluded that there was a discernable region­ geologie history. Hadley and Nelson's work in western wide stratigraphy. The major units in his stratigraphy in North Carolina was based primarily on information the Asheville Folio are: gained from previous mapping in and around the Great Cambrian and Ordovician.