Bedrock geologic map of the northern half of the Moffitt Hill 7.5-minute quadrangle, McDowell, Rutherford and Buncombe counties, North Carolina

North Carolina Department of Environmental Quality Divison of Energy, Mineral and Land Resources S. Daniel Smith, Director Kenneth B. Taylor, State Geologist CORRELATION OF MAP UNITS bzmp bzpg mx Mylonite / Phyllonite Porphyroclastic biotite gneiss Mixed gneiss Metasedimentary Rocks Zss Metasandstone INTRODUCTION The Moffitt Hill 7.5-minute quadrangle lies in western North Carolina in portions of Buncombe, McDowell, and Rutherford counties. Within the quadrangle are the communities of Old Fort, Moffitt Hill, Davistown, and Lackey Town. Portions of the quadrangle in the northwest are owned by the U.S. Forest Service, including a popular hiking trail to Catawba Falls. Interstate 40 is the major transportation corridor on the quadrangle. Major streams include the Catawba River, Crooked Creek, and Cedar Creek. Total elevation relief is 2,547 ft with a low of 1 ,057 ft along the Cedar Creek and a high of 3,604 ft at Stone Mountain along the Rutherford and Buncombe county line. GEOLOGIC OVERVIEW Bedrock of the Moffitt Hill quadrangle comprises the following units (from northwest to southeast): Neoproterozoic metasandstone; porphyroclastic biotite gneiss of unknown affinity; mylonite/phyllonite of the Brevard Fault Zone; and a mixed gneiss unit with several rock types including Tallulah Falls biotite gneiss, Ordovician Henderson Gneiss, and felsic gneiss. The Brevard Zone is a prominent NE-SW-striking feature on the Moffitt Hill quadrangle. The Brevard Zone is a linear fault zone that extends from Alabama to Virginia. It has a complex history of multiple reactivations with the earliest movement during the Neoacadian orogeny. This first movement was ductile and high-temperature with an oblique to strike-slip motion. During the Alleghanian orogeny, the Brevard fault reactivated with ductile strike-slip motion reaching greenschist-facies conditions, and later, experienced brittle dip-slip motion (Hatcher et al., 2007). Ductile shearing attributed to Brevard Zone deformation is observed in a zone several miles wide. Stratigraphic relationships are unclear but the oldest unit on the quadrangle is interpreted to be the porphyroclastic biotite gneiss. It outcrops in the Moffitt Hill quadrangle immediately northwest of the Brevard Zone mylonite/phyllonite and mixed gneiss units. Porphyroclasts within the unit are granule- to gravel-sized and circular, tending to be less ovoid and less elongate in the foliation plane than outcrops of the Henderson Gneiss. This unit is of unknown age and affinity but projects along strike to the northeast into Mesoproterozoic gneisses mapped by Bryant and Reed (1970). Northwest of the porphyroclastic gneiss, the quadrangle is underlain by Neoproterozoic metasandstone The metasandstone was complexly deformed and metamorphosed to amphibolite facies conditions during Taconic orogenesis. These older Taconic fabrics have been overprinted by ductile shearing of the Brevard Zone during the Neoacadian and Alleghanian orogenies. Southeast of the Brevard zone, the mixed gneiss unit contains biotite gneisses possibly correlative to the Tallulah Falls formation mapped to the SE by Bream (1999). Intense deformation of the Brevard zone makes delineation and identification of the protoliths of the mixed gneiss unit difficult. Biotite gneisses within the unit are heterogeneous and contain local granule- to gravel-sized porphyroclasts, ribboned felsic layers, boudined pegmatite layers, and granitic orthogneiss. Possibly interlayered within the biotite gneiss are intrusions of the Ordovician Henderson Gneiss, a large granitic pluton that extends from SC to the NC piedmont. In its type locality the Henderson Gneiss is homogeneous and contains plentiful K-feldspar augens that are elongate with the foliation. Moecher et al. (2011 ) reported the age of the Henderson Gneiss as 447.6 Ma. Mylonitic and non-mylonitic foliations within the quadrangle dominantly strike NE-SW and dip to the SE. The prominent fracture set strikes NW-SE and is steeply dipping. A minor fracture set strikes NE-SW and is steeply dipping. DESCRIPTION OF MAP UNITS1 bzmp Mylonite / phyllonite — Intensely deformed rocks with unknown protoliths. Tan to light-gray to dark-gray to light-olive-gray, to greenish-gray; fine- to coarse-grained; lepidoblastic to porphyroblastic; strongly foliated; mylonitic, locally ultramylonitic, locally brecciated; consists of sericite, quartz, feldspar, biotite, chlorite, and accessory graphite, garnet, sulfides, magnetite, and opaque minerals. Lenticular muscovite-aggregate porphyroblasts flattened in the mylonitic foliation planes impart a distinctive “fish scale” or “button” appearance to phyllonites. Locally interlayered with porphyroclastic biotite gneiss, granitic orthogneiss, and felsic gneiss. bzpg Porphyroclastic biotite gneiss — Heterogeneous mix of porphyroclastic and porphyroblastic, mylonitic biotite gneiss, quartzo-feldspathic gneiss, granitic orthogneiss, felsic gneiss, phyllonite, mylonite, and amphibolite, with minor biotite metawacke and metasandstone. Protoliths unknown although tentatively correlated to Mesoproterozoic gneisses mapped along strike to the northeast. Biotite gneiss is typically light-gray to grayish-black; well foliated; locally protomylonitic to ultramylonitic; medium- to coarse-grained; inequigranular; 2-10 mm sized porphyroblasts and/or porphyroclasts; lepidoblastic; consists of quartz, plagioclase, biotite, potassium feldspar, muscovite, minor epidote, garnet, and titanite. Mixed Gneiss — Heterogeneous unit consisting of a biotite gneiss of unknown affinity, Henderson gneiss, granitic orthogneiss, and mylonite. Biotite gneiss — Dark-gray to grayish-black; fine- to coarse-grained; well foliated; protomylonitic to mylonitic; inequigranular; porphyroclastic with clasts up to 10 mm in diameter and locally porphyroblastic; layering includes ribboned felsic layers and some pegmatite boudins; consists of quartz, plagioclase feldspar, biotite, potassium feldspar, muscovite, and epidote, with minor titanite and garnet. May be correlative to the Tallulah Falls Formation. Henderson Gneiss — Medium-gray to medium-bluish-gray to mottled black and white; inequigranular; medium- to coarse-grained matrix with distinctive megacrysts (augen) of microcline variable in size and abundance; typically protomylonitic to mylonitic, to granoblastic to lepidoblastic; massive to well foliated; dominantly biotite granite that ranges to tonalite; consists of potassium feldspar, plagioclase, quartz, biotite, muscovite and sericite, epidote group minerals, opaque minerals, and trace amounts of titanite, zircon, and apatite; locally pegmatitic and migmatitic. Locally microcline augen exceed 2.5 cm in length. The augen structures are produced by a high temperature protomylonitic overprint. Radiometric age date of approximately 447 Ma (Moecher et al., 2011). Metasedimentary Rocks Zss Metasandstone — Interlayered metamorphosed sandstones with compositions including arkosic arenite, biotite metawacke, and quartzite. Tan to medium-gray to light-green; fine- to medium-grained; foliated to locally mylonitic; equigranular to inequigranular; consists of quartz, feldspar, muscovite, biotite, and minor accessory minerals; notably does not contain schist, amphibolite, or garnet. 1 Mineral abundances are listed in decreasing order of abundance based upon visual estimates of hand samples and thin -sections. WHOLE ROCK ICP ANALYSIS1 OF SELECTED SAMPLES SAMPLE2 COORDINATES3 ROCK TYPE MAP UNIT NB323a 207,763 N 31 5, 509 E porphyroclastic bbtite gneiss bzpg NB323b 207,763 N 31 5, 509 E biotite gneiss bzpg NB323C 207,763 N 31 5, 509 E biotite gneiss and schist bzpg BC459 210.039N 322,717E bbtite gneiss mx MAJOR OXIDES IN PERCENT SiO, ,03 Fe,Q3 MgO CaO Na,0 K,0 Ti02 P,Q, MnO Cr,Q3 LOT Sum' ELEMENTS IN PPM* Ba Ni Sc Be Co Cs Ga HI Nb Rb Sn Sr Та Th U Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Mo Cu Pb Zn Ni As Cd Sb Bi Aq Au Hq Tl Se , i РУ I , 1 Whole Rock Inductively Coupled Plasma - Atomic Emission/Mass Spectrometer analysis conducted by Bureau Veritas, 9050 Shaughnessy St, Vancouver, BC Canada V6P 6E5. 2Sample numbers correspond to thin section and whole rock sample localities shown on geologic map 3State Plane Coordinate System 4LOI = loss on ignition in percent 5SUM = Sum total in percent 6PPM = parts per million. Ni analyzed by Bureau Veritas LF200 and AQ200 procedures. SCHMIDT EQUAL AREA STEREONET DATA N N 180 180 Equal area Schmidt Net projection of contoured poles to foliation. Foliation count 454. Equal area Schmidt Net projection of contoured poles to joints and unidirectional rose diagram inset. Joint count 380. N N Equal area Schmidt Net projection of contoured poles to mylonitic foliation. Mylonitic foliation count 268. Equal area Schmidt Net projection of bearing and plunge of fold hinges in blue and mineral lineations in red. Fold hinge count 24. Mineral lineation count 20. This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program. 82°15'0"W 82°7'30"W 35°37‘30"N 35*37' 30" N Old Fort P1SGAH NATIONAL KOREST lackeflown GREEN COV e Wildcat loffitt sf>7d\ Allison ■■A'e C459 ’dmondson Davistowi fhnAtetov n ИГ-г PUgi&ffKnob wyrpf„ G*frr/toa RIDGECREST № jsant.Ceirv laurel branch dr. ,35°30'0"N 82"15'0'W 322,800 82T30'W ys 39 88 bzmp Topographic base produced by the United States Geological Survey. Altered by the North Carolina Geological Survey for use with this map. * North American Datum of 1983 (NAD83). World Geodetic System of 1984 (WGS84). i Projection:State Plane North Carolina FIPS 3200 (Meters) ' 4,000-meter ticksState Plane North Carolina FIPS 3200 (Nfeters) 6' 48* li 121 MLS 0'41' 12 MILS Image iy . NA1P, July 2014 Roads . U.S. Census Bureau, 2015 - 2016 Roads within US Forest Service Lands . fSTopo Data with limited Fbrest Service updates, 2012- 2016 Nunes . GMS, 2016 Pfydrography. . National Hydrography Dataset, 2014 Contours . National Elevation Datasat, 2008 Boundaries . Multiple sources; see metadatafile 1972- 2016 Wetlands . BVS National Wetlands Inventory 1977 - 2014 UTM GRID AND 201 6 MAGNETO NORTH DECLINATION AT CENTER OF SHEET U.S. National Grid 100,000-m Square ID LV Grid Zone Designation 17S SCALE 1:24000 1 0.5 0 KILOMETERS 1 2 iom l 5Ю 0.5 0 METERS 0 iom 20C0 1 тот о 10C0 20Ш ЗОЮ NILES 40Ю 50Ю 60Ю 70Ш 80C0 90Ю loom FEET CONTOUR INTERVAL 40 FEET NORTH AMERICAN VERTICAL DATUM OF 1988 This map wasproduced to conform with the National Geospatial Program USTopo Product Standard, 201 L A metadata file associated with this product is draft version 0. 6. 19 QUADRANGLE LOCATION 1 Mmtreat 2 Old Fort 3 Marion West 4 Black Nbuntain 5 Sugar №11 6 Bat Cave 7 Lake Lure 8 Shingle Hollow ADJOMN3 QUADRANGLES ROAD CLASSIFICATION Expressway Secondary Hwy Ramp local Connector Local Road 4WD I Interstate Route (LI) FS Primary' Route О US Route FS Passenger Route О State Route FSHgh Clearance Route Check with local Forest Service unit for current travel conditions and restrictions. MOFFITT HILL, NC 2016 REFERENCES Allmendinger, R. W., Cardozo, N., and Fisher, D., 2012, Structural geology algorithms; Vectors and tensors in structural geology: Cambridge University Press, 289 pp. Bream, B.R., 1999, Structural and Stratigraphic Relationships of Ortho- and Paragneisses Southwest of Marion, North Carolina [Master’s Thesis]: Knoxville, University of Tennessee, 155 p. Bryant, B., and Reed, J.C., Jr., 1970, Geology of the Grandfather Mountain window and vicinity, North Carolina and Tennessee: U.S. Geological Survey Professional Paper 615, 190 p. map scale 1 :62,500. Cardozo, N., and Allmendinger, R.W., 2013, Spherical projections with OSXStereonet: Computers & Geosciences, v. 51, p. 193 - 205, d oi : 1 0. 1 01 6/j .cag eo.2 01 2. 07. 02 1. Hurley, B„ 1974, Geologic map of the Southwest Corner of the Marion 15-minute quadrangle, NC, Unpublished geologic map. Hatcher, R.D., Jr., Bream, B.R., and Merschat, A.J., 2007, Tectonic map of the southern and central Appalachians: A tale of three orogens and a complete Wilson cycle, in Hatcher, R.D., Jr., Carlson, M.P., McBride, J.H., and Martinez Catalan, J.R., eds., 4-D Framework of Continental Crust: Geological Society of America Memoir 200, p. 595-632, doi: 10.1130/2007.1200(29). Moecher, D„ Hietpas, J., Samson, S., and Chakraborty, S., 2011, Insights into southern Appalachian tectonics from ages ot detrital monazite and zircon in modern alluvium, Geosphere; v. 7; no. 2; p. 1-19; doi: 10.1130/GES00615.1 3000 2000 1000 Sea Level 0) CD approximate extent of Brevard zone mylonitization Ш > cc c 're c re o о 3000 2000 1000 Sea Level CD CD Fault Contact arrows indicate relative motion along fault T indicates motion toward viewer A Indicates motion away from viewer Research supported by the U.S. Geological Survey, National Cooperative Geologic Mapping Program under STATEMAP (award number - G18AC00205, 2018). The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government. Bedrock Geologic Map of the Northern half of the Moffitt Hill 7.5-minute Quadrangle, McDowell, Rutherford and Buncombe Counties, North Carolina By Bart L. Cattanach, G. Nicholas Bozdog, Sierra J. Isard, and Richard M. Wooten Geology mapped from July 2018 to June 2019. Map preparation, digital cartography and editing by G. Nicholas Bozdog, Bart L. Cattanach, and Sierra J. Isard 2019 This is an Open-File Map. It has been reviewed internally for conformity with North Carolina Geological Survey mapping standards and with the North American Stratigraphic Code. Further revisions or corrections to this Open File map may occur. Some station data omitted from map to improve readability. Please contact the North Carolina Geological Survey for complete observation and thin-section data. North Carolina Geological Survey Open File Report 2019-07 EXPLANATION OF MAP SYMBOLS CONTACTS Zone of Confidence: 300m lllllllll lllllllll ПИШИ HIIIIIH II III III I lllllllll III HI III II III III I I III HI II III llllll ini . Gradational contact-identity and existence certain, location approximate — rTb; у 7 — .? t v— r- 7 Strike-slip fault, right-lateral offset-identity questionable, existence certain, and location accurate. Arrows show relative motion Thrust fault (1 st option)/Strike-slip fault, right-lateral offset — Identity and existence certian, location approximate. Sawteeth on upper (tectonically higher plate). Arrows show relative motion PLANAR FEATURES (For multiple observations at one locality, symbols are joined at the "tail" ends of the strike lines) (Symbols in red taken from Hurley, 1974.) Inclined metamorphic or tectonic foliation — Showing strike and dip У Small, minor inclined joint — Showing strike and dip Inclined metamorphic or tectonic foliation, for multiple observations at one locality — Showing strike and dip Small, minor inclined joint, for multiple observations at one locality — Showing strike and dip У У л Vertical metamorphic or tectonic foliation-Showing strike SmaNi minor vertical or near-vertical joint, for multiple / observations at one locality — Showing strike Inclined mylonitic foliation — Showing strike and dip Inclined generic foliation (origin not specified) — Showing strike and dip Inclined mylonitic foliation, for multiple observations at one locality — Showing strike and dip LINEAR FEATURES (Symbols in red taken from Hurley, 1974.) OTHER FEATURES (Symbols in red taken from Hurley, 1974.) 6 У Inclined aligned-mineral lineation — Showing bearing and plunge О Float station 18 / Inclined slickenline, groove, or striation on fault surface — Showing bearing and plunge NB206 A Thin section and whole rock analysis sample location Inclined fold hinge of generic (type or orientation unspecified) small, minor fold — Showing bearing and plunge Inclined generic (origin or type not known or not specified) lineation or linear structure — Showing bearing and plunge METAMORPHIC AND TECTONIC CONDITIONS • Location where chlorite was observed • Location where garnet was observed Brevard Zone deformation TRAVERSE MAP Hillshade derived from a six meter pixel resolution LiDAR (Light Detecting And Ranging) digital elevation model Red lines show paths of field traverses. Moffitt Hill 7.5-minute Quadrangle, Open File Report 2019-07