Geologic map of the bynum 7.5-minute quadrangle, Orange, Chatham and Alamance Counties, North Carolina

DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCES DIVISION OF ENERGY, MINERAL, AND LAND RESOURCES KENNETH B. TAYLOR, STATE GEOLOGIST ra c i- Ф ro 3 a о о N О (Л ш Qal alluvium 79 1 Э' 35 52' 30' * This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program - « *5/ \79 ©„ NORTH CAROLINA GEOLOGICAL SURVEY OPEN FILE REPORT 2013-03 79 07' 30" 35 52' 30" diabase Metamorphic Rocks / /"'CZgb _ Hunter Mountain dike (Zhm) gabbro to gabbro porphyry dike (CZgb) о о N О w Ш О w О. О QJ East and West Farrington Plutons ca. 579 Ma (Tadlock and Loewy, 2006) Zefg-m Zefg-4 Zwfd Zwfd-gd Zefmd Zwfgd Hyco Formation - upper member metamorphosed plutonic rocks Zgr ca. 613 and 614 Ma (Wortman et al., 2000) metamorphosed volcaniclastic sedimentary and pyroclastic rocks (stratigraphic relations uncertain) ca. 612 -616 Ma (Wortman et al., 2000; Bowman, 2010; and Bradley and Miller, 2011) Hyco Formation - lower member Zhdlt (I) metamorphosed volcaniclastic sedimentary and pyroclastic rocks ca. 633 - 629 Ma (Wortman et al., 2000; Bradley and Miller, 2011) Equal Area Schmidt Net Projection of Contoured Poles to Foliation and Cleavage Contour Interval = 2 sigma N = 277 Equal Area Schmidt Net Projection of Contoured Poles Primary Bedding and Layering Contour Interval = 2 sigma N = 70 35 45' 00' 79 15' 00' 35 45' 00" 79 07' 30" Geology mapped in 2007, summer 2010 and August 2012 through July 2013. 0.5 SCALE 1 :24 000 0 1 i Miles 8 31' 151 MILS 1,000 500 0 1,000 2,000 3,000 4,000 5,000 6,000 19 MILS 7,000 E3 Feet 0.5 1 i Kilometers UTM GRID AND 2010 MAGNETIC NORTH DECLINATION AT CENTER OF SHEET CONTOUR INTERVAL 10 FEET MAP LOCATION Unidirectional Rose Diagram of Joints Joints N = 656 Outer Circle = 5% Mean vector = 283 degrees В INTRODUCTION Pre-Mesozoic crystalline rocks in the Bynum Quadrangle are part of the redefined Hyco Arc (Hibbard et al.. 2013) within the Neoproterozoic to Cambrian Carolina terrane of the Carolina Zone (Hibbard et al., 2002; and Hibbard et al., 2006). In the region of the map area, the Carolina terrane can be separated into two lithotectonic units: l) the Hyco Arc and 2) the Aaron Formation of the redefined Virgilina sequence (Hibbard et al.. 20 13). The Hyco Arc consists of the Hyco Formation which include ca. 612 to 633 Ma (Wortman et al.. 2000; Bowman. 20 10; Bradley and Miller, 20 1 1 ) metamorphosed layered volcaniclastic rocks and plutonic rocks. Available age dates (Wortman et al., 2000; Bradley and Miller, 201 1) indicate the Hyco Formation may be divided into lower (ca. 630 Ma) and upper (ca. 615 Ma) members (informal) with an apparent intervening hiatus of magmatism. In northeastern Chatham County. Hyco Formation units are intruded by the ca. 579 Ma (Tadlock and Loewy, 2006) East Farrington pluton and associated West Farrington pluton. The Aaron Formation (not present in the map area) consists of meta- moiphosed layered volcaniclastic rocks with youngest detrital zircons of ca. 578 and 588 Ma (Samson and Secor. 2001 and Pollock. 2007. respectively). The Hyco Arc and Virgilina sequence lithologies were folded and subjected to low grade metamorphism during the ca. 578 to 554 Ma (Pollock. 2007) Virgilina deformation (Glover and Sinha, 1973; Harris and Glover, I985; Harris and Glover, 1988; and Hibbard and Samson. 1 995). In the map area, original layering of Hyco Formation lithologies are interpreted to range from shallowly to steeply dipping due to open to isoclinal folds that are locally overturned to the southeast. Jurassic-aged diabase dikes intrude the crystalline rocks of the map area. Quaternary-aged alluvium is present in most major drainages. Map units of meta-volcaniclastic rocks include various lithologies that when grouped together are interpreted to indicate general environments of deposition. The dacitic lavas and tuffs unit is interpreted to represent dacitic domes and proximal pyroclastics. The andesitic to basaltic lavas and tuffs unit is interpreted to represent eruption of intermediate to mafic lava flows and associated pyroclastic deposits. The epiclastic/pyroclastic units are interpreted to represent deposition from the erosion of dormant and active volcanic highlands. Some of the meta-volcaniclastic units within the map area display lithologic relationships similar to dated units present in northern Orange and Durham Counties. Due to these similarities, the meta-volcaniclastic units have been tentatively separated into upper and lower portions of the Hyco Formation; geochronologic data is needed to confirm this interpretation. All pre-Mesozoic rocks in the map area have been metamorphosed to at least the chlorite zone of the greenschist metamorphic facies. Many of the rocks display a weak or strong metamorphic foliation. Although subjected to metamorphism, the rocks retain relict igneous, pyroclastic, and sedimentary textures and structures that allow for the identification of protolith rocks. As such, the prefix "meta" is not included in the nomenclature of the pre-Mesozoic rocks described in the quadrangle. Jurassic diabase dikes are unmetamorphosed. Unit descriptions common to Bradley et al. (2007). Bradley and Stoddard (2008). and Bradley and Hanna (2012) from the Farrington, White Cross, and Pittsboro geologic maps, respectively, were used for conformity with on strike units in adjacent quadrangles. The nomenclature of the International Union of Geological Sciences subcommission on igneous and volcanic rocks (IUGS) after Le Maitre (2002) is used in classification and naming of the units. The classification and naming of the rocks is based on relict igneous textures, modal mineral assemblages, or normalized mineral assemblages when whole-rock geochemical data is available. Past workers in the Bynum quadrangle and adjacent areas (Ragland and Butler. 1972; Black. 1977; Hauck, 1977; Allen and Wilson. 1968; and Wagener. 1964 and 1965) have used various nomenclature systems forthe igneous rocks. The select raw data, when available, of these earlier workers was recalculated and plotted on ternary diagrams and classified based on IUGS nomenclature. Pyroclastic rock terminology follows that of Fisher and Schminke (1984). Sterogram plots and calculations created using Stereonet v. 8.6.0 based on Allmendinger et al. (2013) and Cardozo and Allmendinger (2013). DESCRIPTION OF MAP UNITS SEDIMENTARY UNITS Qal Zefg-m Zefg-4 Zefmd Zwfd Zwfd-gd Zwfgd Zgr Zhel Zhe/pl Zhdlt (u) Zhdsi (u) Zhqdp Zhadlt (u) Zhablt Zhablt-dc Zhablt-dcp Zhdlt (I) Qal - Alluvium: Unconsolidated poorly sorted and stratified deposits of angular to subrounded clay, silt, sand and gravel- to cobble-sized clasts, in stream drainages. May include point bars, terraces and natural levees along larger stream floodplains. Structural measurements depicted on the map within Qal represent outcrops of crystalline rock inliers surrounded by alluvium. INTRUSIVE AND META-INTRUSIVE UNITS Jd - Diabase: Black to greenish-black, fine- to medium-grained, dense, consists primarily of plagioclase. augite. and may contain olivine. Occurs as dikes up to 100 ft wide. Diabase typically occurs as spheriodally weathered boulders with a grayish-brown weathering rind. Red station location indicates outcrop or boulders of diabase. CZgb - Gabbro fo gabbro porphyry dike: Dark green to black, melanocratic. medium-grained gabbro to fine-grained, plagioclase porhyritic gabbro porphyry. Present as a dike. Zhm - Hunter Mountain dike: Distinctive, mesocratic, greenish-gray, plagioclase porphyritic (with plagioclase phenocrysts up to 1 cm long) granodiorite to diorite. Matrix is fine-grained consisting of interlocking plagioclase and amphibole (possibly pyroxene) crystals up to 1 mm. Correlated with the Hunter Mountain dike complex of Hauck (1977). FARRINGTON IGNEOUS COMPLEX The Farrington igneous complex consists of several map scale plutons that are grouped into the East and West Farrington plutons. The East Farrington pluton is composed dominantly of granite to granodiorite with several map scale facies with distinct mineral and textural characteristics. U-Pb zircon geochronologic data (Tadlock and Loewy. 2006) indicate that the East Farrington pluton is ca. 579 Ma. The West Farrington pluton is a gradationally zoned composite pluton (Ragland and Butler, 1972) that is characterized by diorite in the northern portions of the map. diorite to granodiorite along its southwestern margins, and leucogranodiorite in the central portions of the pluton. The intrusive relationships between the different phases of the East and West Farrington pluton are not well understood. Based on intrusive relationships observed in outcrop, boulders, and map patterns, it is interpreted that the Zwfd and Zwfd-gd are locally cut by Zwgd. Zefmd locally cuts West Farrington related units and Zefg-m cuts Zefmd. East Farrington pluton Zcfg-m - East Farrington pluton main facies: Leucocratic. orange pink to pinkish-gray to gray, unfoliated, medium- to coarse-grained, equigranular to slightly porphyritic, amphibole (va. hornblende?) granite to granodiorite. Amphibole content varies from approximately 5 to 10% by volume and occurs locally as dark green, elongate crystals up to 1.5 cm long and amorphous intergrowths with feldspar and quartz up to 0.5 cm diameter. Dark gray xenoliths/enclaves up to 8 cm in diameter are common. Grain size becomes finer and xenoliths/enclaves larger near the pluton edge. Cavities, less than 1 mm in diameter, with euhedral terminating crystals are common in some specimens. In thin section the main facies can be separated into txvo groups: 1 ) rocks with a porphyritic texture with orlhoclase and plagioclase phenocryts in a groundmass of intergrown orthoclase, plagioclase and quartz with a granophyric texture (micrographic texture) and 2) porphyritic and equigranular rocks consisting of orthoclase, plagioclase and quartz without a granophyric texture in matrix. The two varieties appear to be intermingled throughout the study area and within the adjacent Farrington Quadrangle (Bradley et al.. 2007). Zefg-4 - East Farrington pluton gray granitoid: Leucocratic to slightly mesocratic. light gray to light greenish-gray, unfoliated to foliated medium-grained granite to granodiorite. White-colored feldspar content is greater than pink feldspars. Foliated specimens have visible white mica growth and less pink feldspars than unfoliated specimens. Foliated rock is present along portions of Pritchards Mill Creek in the Bynum and Farrington quadrangle and Pokeberry Creek and Cumbo Branch in the Farrington Quadrangle. Zefmd - East Farrington monzodiorite porphyry: Leucocratic to mesocratic. light gray to dark grayish-green where fresh, olive drab weathering, plagioclase-phyric monzodiorite and diorite. Fine- to medium-grained groundmass, with phenocrysts to 8 mm. Quartz phenocrysts very rare. Commonly has a cloudy, splotchy, or mottled appearance. Locally contains salmon-colored feldspar phenocrysts and/or orange ovoids interpreted as cavity filling or weathered phenocrysts. May have a thin light beige outer weathering rind. Weathered surface may be pitted. Locally sulfide-bearing, saussuritized, or streaked with tiny epidote veins. Fine-grained near margins. West Farrington pluton: Zw fd - West Farrington pluton diorite: Mesocratic. unfoliated, medium- to coarse-grained, with dark green amphibole (actinolite after hornblende) diorite. Locally with chlorite/biotite; dominantly equigranular but locally weakly plagioclase porphyritic; includes quartz diorite, granodiorite, quartz monzodiorite, and tonalite; commonly contains ovoid enclaves of green to black microdiorite to 0.5 m; grades to local patches of more mafic diorite and gabbro; fine dense to slabby homfelsed country rocks occur locally as enclaves and near contacts; locally strongly saussuritized and pale greenish; white weathering with plagioclase occurring in positive relief giving "bumpy" texture. Zw fd-gd - West Farrinton pluton diorite to granodiorite: Mesocratic to leucocratic, unfoliated, medium- to coarse-grained with dark green amphibole and/or biotite diorite. Quartz content varies locally causing field identification to vary from diorite, quartz diorite, and leucogranodiorite (looks tonalitic locally). Locally with pinkish feldspars. Generally identical to Zwfd but with more intermingled granodiorite with abundant visible quartz. Zwfgd - West Farrington pluton leucogranodiorite: Leucocratic to mesocratic. unfoliated, medium- to coarse-grained, biotite-bearing with dark green amphiboles leucogranodiorite. Quartz content varies locally causing field identification to vary from quartz diorite, leucogranodiorite, to tonalite. Locally with pinkish feldspars. Granophyric texture occurs locally in map area south of Collins Mountain. HYCO FORMATION Metaintrusive rocks associated with Hyco Formation: upper portion ca. 613 and 614 Ma (Wortman et al., 2000) Zgr- Granite: Leucocratic. light brownish to beige or creamy, and locally pale pink or green; medium- to coarse-grained, equigranular metamorphosed leucocratic granodiorite and granite; locally weakly porphyritic with beta-quartz forms; grades to quartz porphyry in zones of cleavage development; quartz may be bluish; locally reddish weathering; locally contains epidote and/or chlorite clots possibly pseudomorphic after a hornblende; feldspar and quartz grains resist weathering and produce a bumpy surface; plagioclase and quartz phenocrysts sit in a granophyric matrix of alkali feldspar and quartz. Correlative to the Chatham granite of Hauck (1977). May be genetically related to Zhqdp unit. Metamorphosed volcaniclastic sedimentary and pyroclastic rocks associated with Hyco Formation: upper portion (stratigraphic relations uncertain), ca. 612 - 616 Ma (Wortman et al.. 2000; Bowman, 2010; and Bradley and Miller. 201 1). Zhel - Epiclastic rocks and lavas: Conglomerate, conglomeratic sandstone, sandstone, siltstone and mudstone. Siltstones and mudstones typically display bedding ranging from mm-scale up to 10 cm, bedding layers traceable for several feet locally, may exhibit soft sediment deformation. Locally tuffaceous with a relict vitric texture. Locally contain interbedded dacitic to basaltic lavas. Conglomerates and conglomeratic sandstones typically contain subrounded to angular clasts of dacite in a clastic matrix. Deposition interpreted as distal from volcanic center, in deep water)?), and via turbidite flows. Correlative in part to Haw River sequence of Hauck ( 1 977). Clasts of Zhablt-dcp occur locally in conglomerates of the unit adjacent to outcrop area of Zhablt-dcp. Zhe/pl-’- Mixed epiclastic-pyroclastic rocks with interlavered dacitic lavas: Grayish-green to greenish-gray, locally with distinctive reddish-gray or maroon to lavender coloration; metamorphosed: conglomerate, conglomeratic sandstone, sandstone, siltstone and mudstone. Lithologies are locally bedded; locally tuftaceous with a relict vitric texture. Siltstones are locally phyllitic. Locally contain interbedded dacitic lavas identical to Zhdlt unit. Contains lesser amounts of fine- to coarse tuff and lapilli tuff with a vitric groundmass. Minor andesitic to basaltic lavas and tuffs present. Silicified and/or sericitized altered rock are locally present. Conglomerates and conglomeratic sandstones typically contain subrounded to angular clasts of dacite in a clastic matrix. Portions of the Zhe/pl unit are interpreted to have been deposited proximal to active volcanic centers represented by the Zhdlt unit but are also interpreted to record the erosion of proximal volcanic centers after cessation of active volcanism. Zhdlt (u) - Dacitic lavas and tuffs of the upper portion of the Hyco Formation: Greenish-gray to dark gray, siliceous, aphanitic dacite. poiphyritic dacite with plagioclase phenocrysts. and flow banded dacite. Dacite with hyaloclastic textures are common. Welded and non-welded tuffs associated with the lavas include: greenish-gray to grayish-green, fine tuff, coarse plagioclase crystal tuff and lapilli tuff. Locally, interlayers of immature conglomerate and conglomeratic sandstone with abundant dacite clasts are present. The dacites are interpreted to have been coherent extrusives or very shallow intrusions associated with dome formation. The tuffs are inteipreted as episodic pyroclastic flow deposits, air fall tuffs or reworked tuffs generated during formation of dacite domes. The unit occurs as map scale pods surrounded by clastic rocks of Zhe/pl and/or Zhel units. Wortman et al. (2000) reports an age of 615.7+3.7/-1.9 Ma U-Pb zircon date fora dacitic tuff from the unit in the Rougemont quadrangle. Zhdsi (u) - Dacitic shallow1 intrusive of the upper portion of the Hyco Formation: Gray-green, light green to green, greenish-gray to light gray; dacite. plagioclase porphyritic dacite with a granular-textured groundmass to micro-granodiorite (intrusive texture visible with 7x hand lens). Locally fine- to medium grained granodiorite present. Plagioclase phenocrysts , when present, range from less than 1 mm to 4 mm. Black colored amphibole. when visible, occurs as phenocrysts (less than 1 mm to 1 mm) and as intergrowths with plagioclase. Amphibole intergrowths distinguish rock from fine-grained tuffs. Interpreted as shallowly emplaced dacite probably co-magmatic with Zhdlt (u) unit. Zhqdp - Quartz dacite porphyry: Strongly porphyritic with aphanitic groundmass and sub- to euhedral phenocrysts (2-6 mm) of white to salmon plagioclase and gray to dark gray (beta-) quartz; phenocrysts typically constitute 20 to 25% of the rock; local weak alignment of plagioclase; interpreted as either lava flows or shallow intrusives possibly associated with domes. Zhadlt (u) - Andesitic to dacitic lavas and tuffs of the upper portion of the Hyco Formation: Black to dark gray, gray-green to green; aphanitic andesite to dacite and porphyritic andesite to dacite with plagioclase phenocrysts. Hyaloclastic textures are common. Interlayed with the lavas are gray to black; welded and non-welded; coarse tuff, lapilli luff, and tuff breccia. Locally interlayered with meta-sediments identical to adjacent Zhe/pl and/or Zhel units. Rocks interpreted as andesites have distinct interior weathering rind of light brown to gray and fresh surfaces exhibit weakly vitric like textures in contrast to dacites. Homfels of unit present near contact with West Farrington Pluton. Zhablt - Andesitic to basaltic lavas and tuffs: Green, gray -green, gray, dark gray and black; typically unfoliated, amygdaloidal. plagioclase porphyritic, amphibole/pyroxene porphyritic and aphanitic; andesitic to basaltic lavas and shallow intrusions. Hyaloclastic texture is common and imparts a fragmental texture similar to a lithic tuff on some outcrops. Locally interlayered with meta-sediments identical to adjacent Zhe/pl and/or Zhel units. Zhablt-dc - Andesitic to basaltic lavas and tuffs of the Dry Creek area: Green, gray-green, gray, dark gray and black; typically unfoliated, amygdaloidal. plagioclase porphyritic, amphibole/pyroxene poiphyritic and aphanitic; andesitic to basaltic lavas and shallow intrusions. Locally interlayered with meta-sediments identical to the Zhel unit. Clasts ofZhablt-dcp locally occur in conglomerates of the unit adjacent to outcrop area of Zhablt-dcp. Includes rocks of the Dry Creek unit of Hauck (1977). Zhablt-dcp - Andesite to basalt porphyry of the Dry Creek area: Distinctive, green to dark green, andesite porphyry with aphanitic groundmass and euhedral phenocrysts (up to 10 mm) of greenish-white plagioclase; phenocrysts typically constitute 20 to 50% of the rock; local alignment of plagioclase; lesser pyroxene/ amphibole phenocrysts. Green to dark green basalt porphyry with abundant pyroxene (altered to amphiboles) phenocrysts with minor plagioclase phenocrysts. Andesite and basalt porphyries locally amygdaloidal (up to 2 cm), amygdules in filling include calcite, quartz, chlorite, and epidote. Clasts of unit locally occur in conglomerates of Zhel. Same as Dry Creek Porphyry complex of Hauck (1977). Metamorphosed volcaniclastic sedimentary and pyroclastic rocks associated with Hyco Formation: lowerportion ca. 629 - 633 Ma (Wortman et al., 2000 and Bradley and Miller, 201 1) Zhdlt (I) - Dacitic lavas and tuffs of the lower portion of the Hyco Formation: Distinctive gray to dark gray, siliceous, cryptocrystalline dacite. porphyritic dacite with plagioclase phenocrysts, and flow banded dacite. Welded and non-welded tuffs associated with the lavas include: greenish-gray to grayish-green, fine tuff, coarse plagioclase crystal tuff; lapilli tuff; and tuff breccia. The dacites are interpreted to have been coherent extrusives or very shallow intrusions associated with dome formation. The tuffs are interpreted as episodic pyroclastic flow deposits, air fall tuffs or reworked tuffs generated during formation of dacite domes. Wortman et al. (2000) report a 632.9 +2.6/-1.9 Ma zircon date from a sample within the unit in the Chapel Hill quadrangle directly on strike with this unit. REFERENCES: Allen, E.P., and Wilson. W.F.. 1968, Geology and mineral resources of Orange County. North Carolina: Division of Mineral Resources, North Carolina Department of Conservation and Development. Bulletin 81. 58 p. Allmendinger. R. W., Cardozo, N. C., and Fisher. D., 2013. Structural Geology Algorithms: Vectors & Tensors: Cambridge. England. Cambridge University Press, 289 pp. Black, W.W., 1 977, The geochronology and geochemistry of the Carolina Slate belt of north-central North Carolina. Ph.D. thesis. University of North Carolina, Chapel Hill. 1 1 8 p. Bowman, J.D.. 2010.. The Aaron Formation: Evidence for a New Lithotectonic Unit in Carolinia. North Central North Carolina, unpublished masters thesis. North Carolina State University, Raleigh. North Carolina, 1 16 p. Bradley, P.J., Gay. N.K.. Bechtel. R.. and Clark. T.W., 2007, Geologic map of the Farrington 7.5-minute quadrangle, Chatham. Orange and Durham Counties, North Carolina: North Carolina Geological Survey Open-file Report 2007-03. scale 1 :24.000. in color. Bradley. P.J. and Stoddard. E.F., 2008, Geologic map of the White Cross 7.5-minute quadrangle. Orange and Chatham Counties, North Carolina: North Carolina Geological Survey Open-file Report 2008-01, scale 1 :24.000, in color. Bradley, P.J. and Miller, B.V., 2011, New geologic mapping and age constraints in the Hyco Arc of the Carolina terrane in Orange County. North Carolina: Geological Society of America Abstracts with Programs, Vol. 43, No. 2. Bradley, P.J. and Hanna. H.D., 2012, Geologic map of the northern portion of the Pittsboro 7.5-minute Quadrangle, Chatham County, North Carolina: North Carolina Geological Survey Open-file Report 2012-03, scale 1:24,000. in color. Cardozo, N. and Allmendinger, R. W., 2013. Spherical projections with OSXStereonet: Computers & Geosciences, v. 51. no. 0, p. 193 - 205. doi: 10.1 01 6/j.cageo.20 12.07.021 . Fisher, R.V. and Schmincke H.-U., 1984, Pyroclastic rocks, Berlin, West Germany, Springer- Verlag, 472 p. Glover, L.. and Sinha, A., 1973, The Virgilina deformation, a late Precambrian to Early Cambrian (?) orogenic event in the central Piedmont of Viiginia and North Carolina. American Journal of Science, Cooper v. 273-A. pp. 234-251. Harris, C.. and Glover. L.. 1 985. The Virgilina deformation: implications of stratigraphic correlation in the Carolina slate belt, Carolina Geological Society field trip guidebook. 36 p. Harris. C.. and Glover. 1988, The regional extent of the ca. 600 Ma Virgilina deformation: implications of stratigraphic correlation in the Carolina terrane. Geological Society of America Bulletin, v. 100. pp. 200-217. Hauck. S.A.. 1977, Geology and petrology of the northwest quarter of the Bynum quadrangle, Carolina slate belt. North Carolina, unpublished M.S. thesis. University of North Carolina at Chapel Hill. 146 p. Hibbard. J., Samson. S., 1995. Orogenesis exotic to the Iapetan cycle in the southern Appalachians, In. Hibbard. J., van Staal. C., Cawood. P. editors. Current Perspectives in the Appalachian- Caledonian Orogen. Geological Association of Canada Special Paper, v. 41 . pp. 191-205. Hibbard. J., Stoddard. E.F., Secor, D., Jr., and Dennis, A., 2002, The Carolina Zone: Overview of Neoproterozoic to early Paleozoic peri-Gondwanan terranes along the eastern flank of the southern Appalachians: Earth Science Reviews, v. 57, n. 3/4, p. 299-339. Hibbard. J. P.. van Staal. C. R.. Rankin. D. W., and Williams, H., 2006. Lithotectonic map of the Appalachian Orogen, Canada-United States of America, Geological Survey of Canada. Map-2096A. 1 : 1.500. 000-scale. Hibbard. J., Pollock, J.. and Bradley, P. 2013, One arc, two arcs, old arc. new arc: The Carolina terrane in central North Carolina . in Hibbard. J.. editor. One arc, two arcs, old arc. new arc; A 21st century perspective on the geology of the Carolina terrane in North Carolina. Carolina Geological Society Field Trip Guidebook for the 2013 annual meeting. Le Maitre. R.W.. Ed., 2002, Igneous Rocks: A Classification and Glossary of Terms: Recommendations of the International Union of Geological Sciences (IUGS) Subcommission on the Systematics of Igneous Rocks: Cambridge, Cambridge University Press, 252 p. Pollock. J. C., 2007. The Neoproterozoic-Early Paleozoic tectonic evolution of the peri-Gondwanan margin of the Appalachian orogen: an integrated geochronological. geochemical and isotopic study from North Carolina and Newfoundland. Unpublished PhD dissertation. North Carolina State University, 194 p. Ragland. PC. and Butler, J.R., 1972, Crystallization of the West Farrington pluton. North Carolina. U.S.A.. Journal of Petrology, vol. 13, No. 3. pp. 381-404. Samson, S.D. and Secor, D., 2001. Wandering Carolina: Tracking exotic terranes with detrital Zircons, GSA Abstracts with Programs Vol. 33, No. 6, p. A-263 Tadlock. K.A. and Loewy, S.L., 2006, Isotopic characterization of the Farrington pluton: constraining the Virgilina orogeny, in Bradley, P.J., and Clark, T.W., eds.. The Geology of the Chapel Hill. Hillsborough and Efland 7.5-minute Quadrangles, Orange and Durham Counties, Carolina Terrane. North Carolina, Carolina Geological Society Field Trip Guidebook for the 2006 annual meeting, pp. 17-21. Wagener, H.D., 1 964. Areal modal variation in the Farrington igneous complex, Chatham and Orange counties. North Carolina, unpublished M.S. thesis. University of North Carolina at Chapel Hill. 5 1 p. Wagener, H.D.. 1 965. Areal modal variation in the Farrington igneous complex, Chatham and Orange Counties, North Carolina. Southeastern Geology, v. 6. no. 2. p. 49-77. Wortman, G.L., Samson, S.D.. and Hibbard. J.P., 2000, Precise U-Pb zircon constraints on the earliest magmatic history of the Carolina terrane. Journal of Geology, v. 108. pp. 321-338. EXPLANATION OF MAP SYMBOLS CONTACTS Lithologic contacts - Distribution and concentration of structural symbols indicates degree of reliability. contact - location inferred contact - location concealed brittle fault - location inferred cross section line — J - anticline, plunging - - 1 - — 4*. — - ^jL - syncline, plunging overturned anticline, plunging overturned syncline, plunging in cross section, inferred axial trace of large-scale fold diabase dike - location inferred diabase dike - location concealed in cross section, diabase dike in cross section, fold form lines of non-cylindrical asymmetric folds PLANAR FEATURES B’ У strike and dip of primary bedding and/or layering ay V/« strike and dip of primary bedding and/or layering (multiple observations at one location) 42/ у V strike and dip of inclined overturned primary bedding У У strike and dip of primary volcanic compaction and/or welding foliation av 7 У strike and dip of inclined regional foliation 80,//X strike and dip of inclined regional foliation (multiple observations at one location) X X strike of vertical regional foliation strike and dip of cleavage strike and dip of cleavage (multiple observations at one location) strike and dip of inclined joint surface strike and dip of inclined joint surface (multiple observations at one location) strike of vertical joint surface strike of vertical joint surface (multiple observations at one location) P50-C22 155-C23 164-E2 156-C31 43-A13 038-D12 47-B3 «8-В5 21-D5 i:34-F5 ■fSH-84 XSH-180 *SH-93-l SH-73F SH-221 QAP plot of normalized whole rock geochemical analyses of select samples from past workers in quadrangle. Analyses with prefix of "SH" from Hauck and Drez (unpublished data, 1977). Remaining analyses from Ragland and Butler (1972). Data provided in analytical table on map. Sample Source Map Unit Si02 ТЮ2 AI203 Fe203 FeO MnO MgO CaO Na20 K20 H20 Total 8-B5 Ragland and Butler (1972) Zefg-m 71.5 0.42 14.40 1.43 1.54 0.10 0.55 1.44 4.84 3.60 NA 99.82 21-D5 Ragland and Butler (1972) Zefg-m 72.1 0.40 14.00 1.44 1.08 0.08 0.50 1.30 4.60 3.73 NA 99.23 34-F5 Ragland and Butler (1972) Zefg-m 71.5 0.44 14.70 1.60 1.65 0.09 0.51 1.16 5.34 3.67 NA 100.66 43-A13 Ragland and Butler (1972) Zwfd 61.9 0.85 14.90 2.52 4.50 0.13 2.82 5.11 3.75 1.88 NA 98.36 47-B3 Ragland and Butler (1972) Zwfd 55.8 1.95 13.80 4.79 5.48 0.22 4.08 7.30 3.57 1.83 NA 98.82 50-C22 Ragland and Butler (1972) Zwfgd 66.1 0.62 14.40 1.36 3.84 0.10 1.89 3.82 3.25 3.13 NA 98.51 55-C23 Ragland and Butler (1972) Zwfgd 69.0 0.52 14.50 2.18 2.40 0.09 1.81 3.65 3.18 2.92 NA 100.25 56-C31 Ragland and Butler (1972) Zwfgd 65.9 0.70 14.00 2.00 3.98 0.10 2.14 3.92 3.21 2.90 NA 98.85 58-D12 Ragland and Butler (1972) Zwfd-gd 62.9 0.73 14.60 2.09 4.49 0.15 2.59 4.77 3.32 2.43 NA 98.07 64-E2 Ragland and Butler (1972) Zwfgd 69.1 0.53 14.30 2.22 2.95 0.08 1.74 3.44 3.48 2.79 NA 100.63 SH-73-F Hauck and Drez (unpublished data, 1977) Zhablt-dcp 57.99 0.90 18.59 4.50 1.39 0.14 1.66 5.73 2.18 3.84 3.56 100.48 SH-221 Hauck and Drez (unpublished data, 1977) Zhablt-dcp 57.75 0.88 18.19 3.99 1.91 0.09 1.73 5.61 3.32 2.89 1.80 98.16 SH-84 Hauck and Drez (unpublished data, 1977) Zhablt-dc 47.17 0.97 19.58 6.28 3.25 0.18 5.27 8.69 2.85 0.72 3.60 98.56 SH-93-1 Hauck and Drez (unpublished data, 1977) Zhdlt (u) 71.81 0.62 14.33 1.73 1.30 0.07 0.42 1.87 6.26 0.81 0.93 100.15 SH-180 Hauck and Drez (unpublished data, 1977) Zgr 72.29 0.33 13.81 0.70 1.61 0.08 0.57 1.98 4.10 3.01 2.05 100.53 X © indicates location of vuggy quartz or siliceous breccia float OTHER FEATURES prospect pit - Au Д # diabase station location geochemical station location station location 47-B3 0 NA = Not analyzed for parameter See Ragland and Butler (1972) for specific analytical methods Hauck and Drez samples analyzed at University of North Carolina - Chapel Hill by X-ray fluorescence, colorimetry, and atomic absorption spectrophotometry Base map is from USGS 2010 GeoPDF of the Bynum 7.5-minute quadrangle. Aerial photo, map collar and select features removed. Bounds of GeoPDF based on 7.5-minute grid projection in UTM 1 7S; North American Datum of 1983 (NAD83). This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program, award numbers G10AC00425 and G12AC20308. 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. This map and explanatory information is submitted for publication with the understanding that the United States Government is authorized to reproduce and distribute reprints for governmental use. Disclaimer: This Open-File report is preliminary and has been reviewed internally for conformity with the North Carolina Geological Survey editorial standards. Further revisions or corrections to this preliminary map may occur. by car by foot GEOLOGIC MAP OF THE BYNUM 7.5-MINUTE QUADRANGLE, ORANGE, CHATHAM AND ALAMANCE COUNTIES, NORTH CAROLINA By Philip J. Bradley, Heather D. Hanna, Edward F. Stoddard, and Randy Bechtel Digital representation by Michael A. Medina, Philip J. Bradley and Heather D. Hanna 2013 Scan with smartphone for link to GeoPDF of map. Third party App required. GEOLOGIC MAP OF THE BYNUM 7.5-MINUTE QUADRANGLE, ORANGE, CHATHAM AND ALAMANCE COUNTIES, NORTH CAROLINA NCGS OPEN FILE REPORT 2013-03