Geologic map of the Saxapahaw 7.5-minute quadrangle, Alamance and Orange counties, North Carolina

North Carolina Department of Environmental Quality Division of Energy, Mineral and Land Resources Brian L. Wrenn, Division Director Kenneth B. Taylor, State Geologist This Geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program North Carolina Geological Survey Open File Report 2022-02 alluvium \ JcK\ 1 diabase Correlation of Map Units INTRODUCTION The Saxapahaw 7.5-minute Quadrangle lies in the east-central portion of the North Carolina Piedmont. The Haw River bisects the quadrangle from the northwest corner to the southeast corner of the quadrangle; the Alamance - Orange County line crosses the eastern portion of the quadrangle from north to south. The county line follows the Haw River in the southeast of the quadrangle. The northeastern portion of the quadrangle is crossed by the northwest-southeast trending NC Highway 54. NC Highway 87 crosses the southwestern portion of the quadrangle. CAROLINA TERRANE Plutonic Rocks Layered and Stratified Rocks ALBERMARLE ARC UWHARRIE FORMATION Zue/pl-A The quadrangle drains to the Haw River along two tributaries of the same name - Cane Creek (one on the west side of the Haw and the other on the east side of the Haw), Marys Creek, Varnals Creek, Meadow Creek, Motes Creek and other named and unnamed creeks. Natural exposures of crystalline rocks occur mainly along these and numerous unnamed creeks. Rock exposure at road cuts, ridges, resistant finned-shaped outcrops and pavement outcrops occur locally outside of drainages. The elevations in the map area range from above 770 feet above sea level on a ridge near the northeast corner of the map southwest of HWY 54 (underlain by the resistant Zhdlt unit); to less than 390 feet along the Haw River near the southeastern corner of the quadrangle. VIRGILINA SEQUENCE Geologic Background and Past Work Farrington Igneous Complex Zwfd West Farrington pluton Zsgr Saxapahaw Pluton (stratigraphic position uncertain) Hyco Arc Plutons Zcgr Zgr-gd HYCO ARC Metavocanic and Metavolcaniclastic Units Hyco Formation - upper portion ca. 616 -612 Ma (Wortman et al., 2000; Bowman, 2010; and Bradley and Miller, 2011) Hydrothermally altered units Zhhar Zhat Zhat/vcs — Zhe/p -Г-. - Zhdlt (u) Zhdlt-a — * - Я — ” Zhe/pl Zhdsi (u) Zhqdp sz Q. CD to 55 Hyco Formation - lower portion ca. 633 - 629 Ma (Wortman et al., 2000 and Bradley and Miller, 2011) Pre-Mesozoic crystalline rocks in the Saxapahaw Quadrangle are part of the redefined Hyco Arc (Hibbard et al., 201 3) within the Neoproterozoic to Cambrian Carolina terrane (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: 1) the Hyco Arc and 2) the Aaron Formation of the redefined Virgilina sequence (Hibbard et al., 2013). The Hyco Arc consists of the Hyco Formation which includes ca. 612 to 633 Ma (Wortman et al., 2000; Bowman, 2010; Bradley and Miller, 2011) metamorphosed layered volcaniclastic rocks and plutonic rocks. Available age dates (Wortman et al., 2000; Bradley and Miller, 2011) indicate the Hyco Formation may be divided into lower (ca. 630 Ma) and upper (ca. 615 Ma) portions with an apparent intervening hiatus of magmatism. In northeastern Chatham County, Hyco Formation units are intruded by the East Farrington pluton and associated West Farrington pluton. Two age dates are available for the East Farrington Pluton: a recent date of 569.0 ±1.1 Ma from Goliber (2020) and a previous date of ca. 579 Ma from Tadlock and Loewy (2006). The Aaron Formation consists of metamorphosed layered volcaniclastic rocks with youngest detrital zircons of ca. 578 and 588 Ma (Samson et al., 2001 and Pollock, 2010, respectively). The Hyco Arc and Aaron Formation lithologies were folded and subjected to low-grade metamorphism during the ca. 578 to 554 Ma (Pollock, 2007; Pollock et al., 2010) Virgilina deformation (Glover and Sinha, 1973; Harris and Glover, 1985; Harris and Glover, 1988; and Hibbard and Samson, 1995). In the map area, original layering of Hyco and Aaron Formation lithologies is interpreted to range from shallowly to steeply dipping due to open to tight folds that are locally overturned to the southeast. Map units of metavolcanic and metavolcaniclastic 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 (with tuffs or conglomerates) units are interpreted to represent eruption of intermediate to mafic lava flows and associated pyroclastic and/or epiclastic deposits. The epiclastic/pyroclastic units are interpreted to represent deposition from the erosion of dormant and active volcanic highlands. Some of the metavolcaniclastic units within the map area display lithologic relationships similar to dated units present in northern Orange and Durham Counties. Due to these similarities, the metavolcanic and metavolcaniclastic units have been tentatively separated into upper and lower portions of the Hyco Formation; geochronologic data in the map area is needed to confirm this interpretation. A review of the regional lithologies is summarized in Bradley (2013). Zhft (I) Abundant evidence of brittle faulting at the outcrop scale and large-scale lineaments (as interpreted from hillshade LiDAR data) are present in the map area. The brittle faulting and lineaments are interpreted to be associated with Mesozoic extension. The Colon cross-structure (Reinemund, 1955), located approximately 18 miles to the southeast of the study area, is a constriction zone in the Deep River Mesozoic basin and is characterized by crystalline rocks overprinted by complex brittle faulting. This complex brittle faulting is likely present in the quadrangle. Dikes of Jurassic aged diabase intrude the crystalline rocks of the map area. Quaternary-aged alluvium is present in most major drainages. Mineral Resources There are no active mining activities currently in the quadrangle. Schmidt et al. (2006) identified the Mazejka Gold Prospect (1 shaft) and unnamed "gold prospect pits’’ in the southwestern portions of the quadrangle. The USGS Mineral Resources Data System (MRDS) identified the Allen Prospect for pyrophyllite in the southwestern portion of the quadrangle. Parts of the southern portion of the quadrangle were mapped at reconnaissance-scale and satellite remote sensing as part of the Schmidt et al. (2006) study. The area was identified as containing large zones of high- sulfidation alteration with the potential for pyrophyllite and gold resources. The abandoned Snow Camp Mine for pyrophyllite is located in the adjacent quadrangle to the southwest. Description of Map Units 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. A preliminary review of the area geology is provided in Bradley (2013). Unit descriptions common to Bradley et al. (2022) and Bradley et al. (2008) in the Silk Hope and White Cross geologic maps, respectively, were used for consistency with on-strike units in neighboring quadrangles. Unit descriptions and stratigraphic correlations were maintained from adjacent mapping in Orange County (Bradley et al., 2016). The nomenclature of the International Union of Geological Sciences subcommission on igneous and volcanic rocks (IUGS) after Le Maitre (2002) is used in the classification and naming of the units. The classification and naming of the rocks are based on relict igneous textures, modal mineral assemblages, or normalized mineral assemblages when whole-rock geochemical data is available. Pyroclastic rock terminology follows that of Fisher and Schminke (1984). Qal Zsgr Zwfd Zcgr Zgr-gd Zdi Zue/pl-A Zhhar Zhat Zhat/vcs Zhe/p Zhe/pl — 7 — ~ Zhdlt (u) * Zhdlt-a Zhdlt-absi / / / / / Zhdsi (u) Zhqdp Zhft (I) Sedimentary Units Qal - Alluvium: Unconsolidated poorly sorted and stratified deposits of angular to subrounded clay, silt, sand and gravel- to boulder-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 Metaintrusive 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 1 00 ft wide. Diabase typically occurs as spheroidally weathered boulders with a grayish-brown weathering rind. Red station location indicates outcrop or boulders of diabase. Zsgr - Granite to granodiorite of the Saxapahaw pluton: Mainly, leucocratic, medium-grained hypidomorphic granular, granite to granodiorite. Quartz grains are conspicuous and weather in positive relief. Mafic minerals are composed of aggregates of chlorite and epidote (likely from the alteration of biotite). In the northwest portion of the quadrangle, there are several satellite plutons interpreted to be related to the Saxapahaw pluton; they are texturally similar but fine- to medium-grained. Schmidt et al. (2006) interpreted the pluton as being noticeably silicified. Schmidt et al. (2006) reported several whole rock and point count analyses with interpreted rock types included granite, porphyritic granite, granite porphyry, porphyritic granodiorite and quartz monzonite. Based on map pattern and intrusive relationships (high angle truncation of Hyco Formation units), the Saxapahaw pluton may be related to the Farrington pluton family or Albemarle Arc plutonism. Ingle (2003) reported a discordant age from the pluton with an upper intercept of 605 +-7.4 Ma. Zwfd - West Farrington pluton diorite: White to cream-colored, 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 hornfelsed 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. Zcgr - Granite of the Chatham pluton: 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 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). Also mapped by Wilkerson (1978). Zgr-gd - Granite to granodiorite: Leucocratic, fine- to medium-grained, metamorphosed, granite to granodiorite, locally brecciated and altered. Zdi - Diorite: Mesocratic (CI-50), greenish-gray to grayish-green, fine- to medium-grained, metamorphosed, hypidiomorphic granular diorite. Major minerals include plagioclase and amphibole. Plagioclase crystals are typically sericitized and saussuritized. Amphiboles are typically altered to chlorite and actinolite masses. Gabbro intermingled locally. Locally, microdiorite to andesitic-textured rock present. Metavolcanic and Metavolcaniclastic Units Uwharrie Formation Zue/pl-A - Uwharrie Formation mixed epiclastics, pyroclastics and lavas of Alamance County: Grayish-green to greenish-gray, metamorphosed tuffaceous sandstones, conglomeratic sandstones, siltstones and minor phyllite. The siltstones typically are weakly phyllitic. Contains lesser amounts of tuff and intermediate to mafic lavas. Quartz and feldspar crystal fragments are common in the sedimentary components, tuffs and lavas. Similar looking rocks in Chatham County yielded an U-Pb zircon age of 548.7 ±1.1 Ma (Goliber, 2020). The unit is interpreted to be in unconformable contact with adjacent Hyco Formation units. Hyco Formation Zhhar - Hydrothermally altered rocks: Mixed unit of hydrothermally altered rocks consisting of: dense siliceous cryptocrystalline rock; quartz-pyrophyllite rocks, +- kaolinite, andalusite, chloritoid, sericite, paragonite and iron oxides; quartz-sericite rocks, +- paragonite, k-feldspar and iron oxides; and quartz-chloritoid-chlorite rocks, +- sericite and hematite. Described in detail by Hughes (1987) and Schmidt et al. (2006). Zat- Altered tuffs: Very light gray to light greenish-gray (whitish in areas) with red and yellow mottling. Alteration consists of silicified, sericitized and pyrophyllitized rock. Sericite phyllite, pods of pyrophyllite, and quartz + pyrophyllite rock all with less than c1 mm to 2 mm diameter weathered sulfides are common. Fine-grained chloritoid porphyroblasts (less than 1 mm) are present in some pyrophyllite bearing rocks. Relict lithic clasts and kaolinitized feldspar crystal shards are visible in some exposures. Relict structures are obliterated in heavily altered rocks. Map area contains boulders (up to several feet in diameter) and outcrop of massive milky quartz and quartz + sericite rock. Zhat/vcs: Altered tuffs and volcaniclastic sedimentary rocks: Mixed unit of altered volcaniclastic rocks and volcaniclastic sedimentary rocks. Alteration consists of silicified, sericitized and pyrophyllitized rock. Chloritoid locally present. Volcaniclastic sedimentary rocks include conglomeratic siltstone to conglomerate that may be variably altered. Includes area of quartz-sericite-paragonite rock (Zvqs) of Schmidt et al. (2006). Massive quartz locally present. Zhe/p - Mixed epiclastic-pyroclastic rocks: Green, grayish-green to greenish-gray; tuffaceous sandstones, conglomeratic sandstones, siltstones and minor phyllite. The siltstones typically are weakly phyllitic. Contains lesser amounts of coarse tuff and lapilli tuff. Silicified and/or sericitized altered rock similar to Zat unit are present near contacts with other units. Minor andesitic to basaltic lavas and tuffs. Zhe/pl - Mixed epiclastic-pyroclastic rocks with interlayered 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 tuffaceous with a cryptocrystalline-like groundmass. 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 cryptocrystalline-like groundmass. Pyroclastics, lavas, and epiclastics are mainly felsic in composition. Minor andesitic to basaltic lavas and tuffs present. Silicified and/or sericitized altered rock are locally present and increase in occurrence toward the north. Conglomerates and conglomeratic sandstones typically contain subrounded to angular clasts of dacite in a clastic matrix. Fine- to medium-grained diorite is locally present. 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. Zhp/e - Mixed pyroclastic-epiclastics: Gray to green, felsic tuffs interlayed with mudstone, siltstone, and sandstone and distinctive immature, monomictic, conglomeratic sandstone to conglomerate containing subangular to angular clasts of plagioclase porphyritic dacite. Minor andesitic to basaltic lavas and tuffs. Zhabsi - Andesitic to basaltic shallow intrusive of the Hyco Formation: Grayish-green to light green, metamorphosed: plagioclase porphyritic andesite to basalt with a granular-textured groundmass to very fine-grained diorite and gabbro (with intrusive texture visible with 7x hand lens - microdiorite/microgabbro). Contains lesser amounts of fine- to medium-grained diorite and gabbro. Plagioclase phenocrysts typically range from 1 mm to 4 mm. Dark green to black colored amphibole, when present, occur as phenocrysts (less than 1 mm to 1 mm) and as intergrowths with plagioclase. 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 pyroclastic rocks and meta-sediments identical to the Zhe/pl unit. Zhdlt (u) - Dacitic lavas and tuffs of the upper portion of the Hyco Formation: Greenish-gray to dark gray, siliceous, metamorphosed: aphanitic dacite, porphyritic dacite with plagioclase phenocrysts, and flow banded dacite. Dacite with hyaloclastic textures is 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 interpreted 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 unit. Wortman et al. (2000) reports an age of 615.7+3.7/-1.9 Ma U-Pb zircon date for a dacitic tuff from the unit in the Rougemont quadrangle. Zhdlt-a - Altered dacitic lavas and tuffs of the Hyco Formation: Very light gray to light greenish-gray (whitish in areas) with red and yellow mottling, altered and metamorphosed dacitic lavas and tuffs. Alteration consists of silicified, sericitized and pyrophyllitized rock. Relict structures are obliterated in heavily altered rocks. Zhdlt-absi - Dacitic lavas and tuffs of the Hyco Formation infested by andesitic to basaltic dikes: Mixed unit of metamorphosed dacitic lavas and tuffs of the Zhdlt unit intruded by plagioclase porphyritic andesite to basalt. Zhdsi (u) - Dacitic shallow 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 Zdlt (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. Zhft (I) - Felsic tuffs: Grayish-green to greenish-gray and silvery-gray; massive to foliated volcaniclastic pyroclastic rocks consisting of fine- to coarse tuffs, lapilli tuffs and minor welded tuffs. Tuffs are differentiated from other volcaniclastic rocks by the presence of zones of cryptocrystalline texture that exhibit conchoidal-like fractures in between foliation domains. Layering ranges from massive to thinly bedded. Contains lesser amounts of volcaniclatic sedimentary rocks consisting of volcanic sandstones, and greywackes with minor siltstones and phyllite. EXPLANATION OF MAP SYMBOLS Zhdlt (u) me ТусПу Airport Zhdlt (u) Zue/pl-A Zhdlt (u; Zhdlt (u) Zhdlt-absK Zhdlt (u) Zhdsi (u) Zhdlt (u) V cores Chisel Cem Zhat/vcs Zhdlt-a Prospects (AU)X*) Zhdsi (u) Zhat/vcs Allen Zhhar ?7. Zhdlt (u) Zhdsi (u) Zhhar Zhat/vcs 7ЯО CHAPEL HIL Zhhar Zhablt Zhat/vcs 2 88 Zhat/vcs Zhdlt (u) Zhablt. Zhhar Mazejka Gold Prospect (AU) Zhat/vcs 650 Zhdlt (u) 79° 15’ 00” Altered by the North Carolina Geological Survey for this map Produced by the United States Geological Survey North American Datum of 1983 (NAD83) World Geodetic System of 1984 (WGS84). Projection and 1 000-meter grid:Uni»ersal Transverse Mercator, Zone 17S This map is not a legal document. Boundaries may be generalized for this map scale. Private lanet within gavernment reservations may not be shown. Obtain permission before entering private lands. Imagery . NAIP. May 2016 - November 2016 Roads . U.S. Census Bureau, 2016 Names . GNIS, 1980 - 2019 Hydrography . National Hydrography Dataset, 1899 - 2018 Contours . National Elevation Dataset, 2008 Boundaries . -Multiple sources; see metadata file 2017 - 2018 Wetlands . FWS National Wetlands Inventory 1982 - 1983 UTM GRID AND 2019 MAGNETIC NORTH DECLINATION AT CENTER OF SHEET U S National Grid 0,000 - m Square II PV nd Zone Oesonatlon 17S SCALE 1:24 000 1 0.5 0 KILOMETERS 1 1000 500 0 METERS 1000 1 0.5 0 MILES 1000 0 1000 2000 3000 4000 5000 6000 7000 8000 . — ■ ■ — ■ ■ — ■ f — ■ ■ - . ■ ■ ■ — a FEET 2 2000 1 9000 10000 CONTOUR INTERVAL 10 FEET NORTH AMERICAN VERTICAL DATUM OF 1988 This map was produced to conform with the National Geospatial Program US Topo Product Standard, 201 1 . A metadata file associated with this product is draft version 0.6.18 QUADROMGIE LOCATION 1 Burlington 2Mebane 3 Efland 4 Snow Camp 5 White Cross 6 Crutchfield Crossroad; 7 Silk Hope 8 8ynum ADJOINING QUADRANGLES 1 2 3 4 5 6 7 8 ROAD CLASSIFICATION Expressway Local Connector Secondary Hwy — — . Local Road Ramp 4WD I Interstate Route ,r ~ US Route State Route SAXAPAHAW, NC CONTACTS, FAULTS, AND OTHER FEATURES inferred contact, dotted where concealed inferred brittle fault, dotted where concealed inferred diabase, dotted where concealed --w-~ surficial units contact _ linear geomorphic feature interpreted from hillshade LiDAR - origin uncertain А' -Л-? cross section line inferred high-angle reverse fault, existence questionable interpreted fold hinge of overturned anticline; dotted where concealed, queried where questionable interpreted fold hinge of syncline; dotted where concealed, queried where questionable interpreted fold hinge of overturned syncline; dotted where concealed, queried where questionable IN CROSS SECTION contact inferred fold axis PLANAR, LINEAR AND OTHER FEATURES ru strike and dip of bedding or layering (multiple observations at one location) ["U strike and dip of cleavage (multiple observations at one location) [46 strike and dip of foliation |i 80 strike and dip of inclined joint + n T г strike of vertical foliation strike and dip of foliation (multiple observations at one location) strike of vertical foliation (multiple observations at one location) cataclastic foliation strike and dip of cleavage I ! b 56 f strike and dip of inclined joint surface (multiple observations at one location) strike of vertical joint strike of vertical joint surface (multiple observations at one location) strike and dip of welding/compaction foliation clast lineation © observation station location • diabase station location & Ingle (2003) SAX-1 age date approximate location References: X prospects [gold (AU) and pyrophyllite (PPY)] 0 whole rock analysis (USGS OFR 2006-1259) . composite rock chip samples f (USGS OFR 2006-1259) Allmendinger, R. W., Cardozo, N. C., and Fisher, D., 2013, Structural Geology Algorithms: Vectors and Tensors: Cambridge, England, Cambridge University Press, 289 pp. 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, 116 p. Bradley, P.J., and Stoddard, E.F., 2008, Geologic map of the White Cross 7.5-minute quadrangle, NCGS Open-file Report 2008-01, scale 1:24,000 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., 2013, The Carolina terrane on the west flank of the Deep River Basin in the northern Piedmont of North Carolina - A Status Report, in Hibbard, J.P. and Pollock, J.C. editors, 2013, One arc, two arcs, old arc, new arc: The Carolina terrane in central North Carolina, Carolina Geological Society field trip guidebook, pp. 139-151. Bradley, P.J., Hanna, H.D., Gay, N.K., Stoddard, E.F., Bechtel, R., Phillips, C.M., and Fuemmeler, S. J, 2016, Geologic map of Orange County, North Carolina: North Carolina Geological Survey Open-file Report 2016-05, scale 1:50,000, in color. Bradley, P.J., Hanna, H.D. and Michael, E.K., 2022, Geologic map of the Silk Hope 7.5-Minute Quadrangle, Chatham and Alamance counties, North Carolina, NCGS Open-file Report 2022-01, scale 1:24,000 (Supersedes NCGS Open-file Report 2014-02). Cardozo, N., and Allmendinger, R. W., 2013, Spherical projections with OSXStereonet: Computers and Geosciences, v. 51, no. 0, p. 193 - 205, doi: 10. 1016/j.cageo.201 2.07.021 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 Virginia and North Carolina, American Journal of Science, Cooper v. 273-A, pp. 234-251. Goliber, S.F.B., 2020, Assessment of the Timing of the Virgilina Deformation with U-Pb Ages of Plutonic and Volcanic Rocks in the Carolina Terrane (unpublished undergraduate thesis), University of North Carolina Chapel Hill, p. 14. Harris, C., and Glover, L., 1985, 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., and Samson, S., 1995, Orogenesis exotic to the lapetan 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. 1 91-205. 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.P., Pollock, J.C., and Bradley, P.J., 2013, One arc, two arcs, old arc, new arc: An overview of the Carolina terrane in central North Carolina, Carolina Geological Society field trip guidebook, 265 p. Hughes, E.H., 1987, The geology and alteration centers of the Snow Camp mine-Major Hill area, central Carolina slate belt, Alamance and Chatham Counties, North Carolina: U.S. Geological Survey Open-File Report 87-180, 29 p. Ingle, S., Mueller, P., Heatherington, A., and Kozuch, M. 2003, Isotopic evidence for the magmatic and tectonic histories of the Carolina terrane: implications for stratigraphy and terrane affiliation. Tectonophysics 371 : 187-211. 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. Pollock, J.C., Hibbard, J.P., and Sylvester, P.J., 2010, Depositional and tectonic setting of the Neoproterozoic-early Paleozoic rocks of the Virgilina sequence and Albemarle Group, North Carolina: in Tollo, R.P., Bartholomew, M.J., Hibbard, J.P., and Karabinos, P.M., eds., From Rodinia to Pangea: The Lithotectonic Record of the Appalachian Region: Geological Society of America Memoir 206, p. 739-772. Reinemund, J.A., 1955, Geology of the Deep River coal field, North Carolina: U.S. Geol. Survey Prof. Paper 246, 159 p. Samson, S.D., Secor, D.T, and Hamilton, M.A., 2001, Wandering Carolina: Tracking exotic terranes with detrital Zircons, GSA Abstracts with Programs Vol. 33, No. 6, p. A-263. Schmidt, R.G., Gumiel, P., and Payas, A., 2006, Geology and mineral deposits of the Snow Camp-Saxapahaw area, Central North Carolina: United States Geological Survey Open-file Report 2006-1259 (http://pubs.usgs.gov/of/2006/1259/index.html). 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., editors, 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. Wilkinson, S.E., 1978, The geology of the northeast quarter of the Silk Hope quadrangle, Carolina Slate belt, North Carolina, unpublished M.S. thesis, University of North Carolina at Chapel Hill, 56 p. 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. Equal Area Schmidt Net Projections and Rose Diagram Plots and calculations created using Stereonet v. 10.2.0 based on Allmendinger et al. (2013) and Cardozo and Allmendinger (2013) Equal Area Schmidt Net Projection of Contoured Poles to Primary Bedding, Layering and Welding/Compaction Foliation in Carolina Terrane Rocks Contour Interval =2 sigma; N=23 Equal Area Schmidt Net Projection of Contoured Poles to Foliation and Cleavage in Carolina Terrane Rocks Contour Interval = 2 sigma; N=218 Unidirectional Rose Diagram of Joints N=503 Outer Circle = 6% Mean vector = 34° no vertical exaggeration for bedrock units Qal thickness exaggerated to be visible Geologic Map of the Saxapahaw 7.5-Minute Quadrangle, Alamance and Orange Counties, North Carolina By Philip J. Bradley, Emily K. Michael, Heather D. Hanna and Edward F. Stoddard Geologic data collected in 2007, summer 2010 and June 2021 to May 2022. Supersedes NCGS OFR 2011-04 Map preparation, digital cartography and editing by Philip J. Bradley, Michael A. Medina and Emily K. Michael 2022 Saxapahaw Base Map Information: Base map is from USGS 2019 GeoPDF of the Saxapahaw 7.5-minute quadrangle. Air photo, map collar, contours and select features removed. Contour lines enhanced in Adobe Acrobat. Bounds of GeoPDF based on 7.5-minute grid projection in UTM 17S; North American Datum of 1983 (NAD83). This geologic map was funded in part by the U.S. Geological Survey, National Cooperative Geologic Mapping Program under STATEMAP (Awards - 2007, 07HQAG0140; 2010, G10AC00425; and 2021 , G21 AC10805). 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. 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. Acknowledgments: Geochemistry point digitization and field support by Amy Pitts (NCGS). TRAVERSE MAP - by foot - by car Geologic Map of the Saxapahaw 7.5-Minute Quadrangle, Alamance and Orange Counties, North Carolina