Geologic map of the Chatham County portion of the Coleridge 7.5-minute quadrangle, Chatham and Randolph Counties, North Carolina

North Carolina Department Of Environmental Quality This Geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program Division of Energy, Mineral and Land Resources North Carolina Geological Survey Open File Report 2018-03 Kenneth B. Taylor, State Geologist & ro c: *— Ф •*-* ш 13 О Qal CORRELATION OF MAP UNITS О О S ъ- ф о L— CL О ф Z Albemarle Arc Pluton Interpreted to be related to the Parks Crossroads pluton - ca. 566 +/- 46 Ma Rb-Sr Zgd Aaron Formation Youngest detrital zircons of ca. 588 and 578 Ma (Pollock et al., 2010 and Samson et al., 2001, respectively) Za Zav1 Zaqdp Hyco Formation - upper portion — Metamorphosed volcaniclastic sedimentary and pyroclastic rocks associated with Hyco Formation: upper portion ca. 616 - 612 Ma. (Wortman et al., 2000; Bowman, 2010; and Bradley and Miller, 2011) Zhime/pl JS ш ET. CQ -s Ш T3 Ф ш *-** o' 33 СЛ c 33 о Ф Д- ш 13 INTRODUCTION The Coleridge 7.5-minute Quadrangle lies in the east central portion of the North Carolina Piedmont. The Randolph - Chatham County line crosses the quadrant from north to south. The Siler City Municipal Airport is located on the eastern side of the quadrangle. The unincorporated community of Coleridge which includes the Coleridge Historic District (part of the National Register of Historic Places) is present in Randolph County on the southwest corner of the quadrangle. The northern portion of the quadrangle is crossed by US Hwy 64, a major east-west corridor for the central Piedmont. State Hwy 22 and 42 are present in the southwest corner of the quadrangle. The majority of the quadrangle drains to the Deep River along drainages that include Reed Creek, Brush Creek, Little Brush Creek, Blood Run, Millstone Creek, Broad Mouth Branch and Back Branch. A small portion of the northeast corner of the quadrangle drains to the Rocky River. 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 about 700 feet above sea level at the end of Knoll Ridge Road near the east-central edge of the quadrangle (on the ridge that marks a major geologic contact between the Hyco and Aaron Formations in the area), to less than 370 feet along the Deep River near the southwest corner of the quadrangle. GEOLOGIC BACKGROUND AND PAST WORK Pre-Mesozoic crystalline rocks in the Coleridge Quadrangle are part of 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 include ca. 633 to 612 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 (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 consists of metamorphosed layered volcaniclastic rocks with youngest detrital zircons of ca. 588 and 578 Ma (Pollock et al., 2010 and Samson et al., 2001 , respectively). FOLDS 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 are interpreted to range from shallowly to steeply dipping due to open to tight folds that are locally overturned to the southeast. Four hundred and seven (407) primary bedding, layering and compaction/welding foliation measurements from this and adjacent quadrangles in the immediate area of the map were used in stereogram analyses to determine the range of fold interlimb angles. Calculated interlimb angles ranged from greater than 120 degrees to less than 30 degrees indicating the presence of gentle to tight folds. Preliminary domainal analyses of measurements in Hyco Formation units only, indicate the folds range from tight to open with the majority of the folds likely within the tight to close range. Preliminary domainal analyses of measurements in Aaron Formation units only, indicate the folds range from tight to gentle with the majority of the folds within the open range. MINERAL RESOURCES There are no active mining activities currently in the quadrangle. Two abandoned quarries utilized for crushed stone are present within the Parks Crossroads Granodiorite (Tingle, 1982). Both abandoned quarries are located in the vicinity of the crossroads of Parks Crossroads. 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. 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). 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 and adjacent quadrangles. The brittle faulting and lineaments are interpreted to be associated with Mesozoic extension. The Colon cross-structure (Reinemund, 1955), located 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. Dikes of Jurassic aged diabase intrude the crystalline rocks of the area. Quaternary aged alluvium is present in most major drainages. A preliminary review of the area geology is provided in Bradley (2013). Unit descriptions common to Bradley et al. (2017a, b) and Bradley et al. (2018) from the Crutchfield Crossroads, Siler City, and Liberty geologic maps, respectively, were used for conformity 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 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. Pyroclastic rock terminology follows that of Fisher and Schminke (1984). Sedimentary Units Qal Jd 4 Zgd Zaqdp Zav1 Za 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 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. Zgd -Granodiorite: (Cl=5) Leucocratic, fine- to medium- grained, equigranular metamorphosed, granodiorite. Mineral assemblage includes quartz, plagioclase, and green hornblende +/- chlorite, +/- epidote. Likely correlative to the Parks Crossroads pluton - ca. 566 +/- 46 ma. Rb-Sr whole rock age (Tingle, 1982). Zaqdp - Quartz dacite porphyry: 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. May locally have fine-grained intrusive texture. Interpreted as either lava flows or shallow intrusives. Similar to quartz dacite porphyry unit within the Bynum Quadrangle (Bradley et al., 2013). Present as isolated outcrops or boulders as designated by pink-colored station locations. Metavolcanic and Metavolcaniclastic Units Aaron Formation Zav1 - Aaron Formation (Virgilina member) volcanics: Mixed epiclastic-pyroclastic rocks with interlayered felsic to mafic lavas: Grayish-green to green; metamorphosed: non-tuffaceous to tuffaceous conglomerate, conglomeratic sandstone, sandstone, siltstone and mudstone. Pyroclastic rocks are grayish-green to greenish-gray and silvery-gray; massive to foliated fine- to coarse 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. Gray to greenish-gray, siliceous, cryptocrystalline dacite and porphyritic dacite with plagioclase phenocrysts. Gray-green, gray, to green; typically unfoliated, amygdaloidal, plagioclase porphyritic, amphibole/pyroxene porphyritic and aphanitic; metamorphosed: andesitic to basaltic lavas and shallow intrusions. Diorite locally intrudes. Za - Aaron Formation: Distinctive metasedimentary package that ranges from fine-grained siltstones to coarse-grained sandstones, pebbly sandstones and conglomerates. Siltstones are similar in appearance to Hyco Formation lithologies. The sandstones, pebbly sandstones and conglomerates [classified as litharenite, feldspathic litharenite and lithic feldsarenite by Harris (1984)] are distinctive and commonly contain rounded to subrounded clasts of quartz ranging from sand- to gravel-sized. In the sandstones, feldspar is the most prominent mineral grain; quartz varies from sparse to abundant in hand sample. Lithic clasts are typically prominent and range from sand- to gravel-size. Harris (1984), performed a detailed sedimentary study of the Aaron Formation to the immediate west of the map area. Harris (1984) interpreted the Aaron Formation to have been deposited by turbidity currents in a retrogradational submarine fan setting. Pollock et al., (2010) interprets an approximate 37 million year unconformity between the Aaron and underlying Hyco Formation. This interpretation is based in part on detrital zircon age date data from an Aaron conglomerate sample collected in the adjacent Liberty Quadrangle. 79°37'30 35“45' - . УО///2-^У 35°37'30 35°37'30" Topographic base produced by the United States Geological Survey. Altered by the North Carolina Geological Survey for use with map. North American Datum of 1983 (NAD83) World Geodetic System of 1984 (WGS84). Projection and 1 000-meter grid: Universal Transverse Mercator, Zone 17S 10 000-foot ticks: North Carolina Coordinate System of 1983 Imagery . NAIP, May 2012 Roads . ©2006-2012 TomTom Names . GNIS, 2012 Hydrography . National Hydrography Dataset, 2012 Contours . National Elevation Dataset, 2008 Boundaries . Census, IBWC, IBC, USGS, 1972 - 2012 Base map is from USGS 2013 GeoPDF of the Coleridge 7.5-minute quadrangle. Air photo, map collar and select features removed. Bounds of GeoPDF based on 7.5- minute grid projection in UTM 17S; North American Datum of 1983 (NAD83). Geologic polygons tied to 7.5- minute grid projection in State Plane coordinates for edge-matching with legacy GIS data, as such some overlap and underlap of map unit polygons occur around edge of map. 7 8' 28 • 154 MILS 0.5 SCALE 1:24 000 0 KILOMETERS ROAD CLASSIFICATION 1000 500 O' 50" IS MILS 05 METERS 0 1000 2000 Expressway Secondary Hwy Ramp Local Connector Local Road 4WD 1000 1000 2000 MILES 3000 4000 5000 I Interstate Route 6000 7000 8000 9000 10000 QUADRANGLE LOCATION О US Route О State Route UTM GRID AND 2013 MAGNETIC NORTH DECLINATION AT CENTER OF SHEET U.S. National Grid t00,0(X)-rn Square 10 PV God Zone Designation 17S FEET 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, 2011. A metadata file associated with this product is draft version 0.6.11 Grays Chapel Liberty Crutchfield Crossroads Ramscur Coleridge Siler City Erect Bennett Bear Creek COLERIDGE, NC ADJOINING 7.5' QUADRANGLES Zhime/pl Hyco Formation - Upper Portion Zhime/pl - Mixed intermediate to mafic epiclastic-pyroclastic rocks with interlayered intermediate to mafic lavas: Grayish-green to green, 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 intermediate to mafic lavas identical to Zhabl, Zhable, and Zhablc units. Contains lesser amounts of fine- to coarse tuff and lapilli tuff with a cryptocrystalline-like groundmass. Pyroclastics, lavas, and epiclastics are mainly intermediate to mafic in composition. Minor dacitic lavas and tuffs present. Silicified and/or sericitized altered rock are locally present. Conglomerates and conglomeratic sandstones typically contain subrounded to angular clasts of andesite and basalt in a clastic matrix. Generally interpreted to have been deposited proximal to active intermediate to mafic composition volcanic centers and/or record the erosion of proximal intermediate to mafic composition volcanic centers after cessation of active volcanism. Zhable - Andesitic to basaltic lavas with interlayered epiclastic rocks: Light green, gray-green, gray, and dark gray; typically unfoliated, amygdaloidal, plagioclase porphyritic, amphibole/pyroxene porphyritic and aphanitic; metamorphosed: andesitic to basaltic lavas and shallow intrusions. Hyaloclastic texture is common and imparts a fragmental texture on some outcrops and float boulders. Contains lesser amounts of grayish-green, light green, and light gray to white; metamorphosed conglomerate, conglomeratic sandstone, sandstone, siltstone and mudstone. Geologic Map of the Chatham County portion of the Coleridge 7.5-Minute Quadrangle, Chatham and Randolph Counties, North Carolina. This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program under StateMap award numbers G15AC00237, 2015 and G17AC00264, 2017. By Philip J. Bradley, Brandon T. Peach, and Heather D. Hanna Geologic data collected in July 201 5 through May 2016 and June 2017 through May 2018. 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. Map preparation, digital cartography and editing by Michael A. Medina, Brandon T. Peach, Heather D. Hanna and Philip J. Bradley. 2018 Supersedes Open-file Report 2016-11 EXPLANATION OF MAP SYMBOLS - Inferred contact Concealed contact CONTACTS Inferred brittle fault. ? indicates - - identity or existence questionable; inferred from LiDAR lineament. - Diabase dike - inferred - Quaternary alluvium contact Interpreted fold hinge anticline, dotted where concealed Linear geomorphic feature interpreted from hillshade LiDAR - origin uncertain Interpreted fold hinge of syncline, dotted where concealed . . In cross section, gradational contact In cross section, inferred fold axis Cross section line PLANAR AND OTHER FEATURES I 68 Strike and dip of primary bedding and/or layering Strike and dip of cleavage Strike and dip of primary bedding and/or layering (multiple observations at one location) Strike and dip of cleavage (multiple observations at one location) ^ 65 + Strike and dip of inclined regional foliation Strike of vertical regional foliation |i si Strike and dip of inclined joint surface re I Strike and dip of inclined joint surface ■ 89 (multiple observations at one location) Strike and dip of inclined regional foliation (multiple observations at one location) Strike of vertical joint surface Strike of vertical joint surface (multiple observations at one location) © Observation station location Indicates location of vuggy quartz or sliceous breccia float • Diabase station location ^ Quarry (crushed stone) - abandoned Indicates location of quartz dacite porphyry boulders or outcrop REFERENCES: 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 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 Peach, B.T., 2017a, Geologic map of Chatham County portion of the Crutchfield Crossroads 7.5- Minute Quadrangle, Chatham and Alamance counties, North Carolina: North Carolina Geological Survey Open-file Report 2017- 10, scale 1:24,000, in color (Supersedes Open-file Report 2016-09). Bradley, P.J., Peach, B.T. and Hanna, H.D 2017b, Geologic map of the Siler City 7.5-Minute Quadrangle, Chatham County, North Carolina: North Carolina Geological Survey Open-file Report 2017-07, scale 1:24,000, in color (Supersedes Open-file Report 2016-08). Bradley, P.J., Peach, B.T., and Hanna, H.D., 2018, Geologic map of the Chatham County portions of the Liberty 7.5-minute Quadrangle, Chatham, Alamance and Randolph Counties, North Carolina: North Carolina Geological Survey Open-file Report 2018-02, scale 1:24,000, in color. 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.2012.07.021. 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 . Harris, C.W., 1984, Coarse-grained submarine-fan deposits of magmatic arc affinity in the late Precambrian Aaron Formation, North Carolina, U.S.A., Precambrian Research, 26, pp. 285-306. 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. 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. 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.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. 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. 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 . Tingle, T.N., 1982. Geology and geochronology of the Parks Crossroads granodiorite near Siler City, central North Carolina Piedmont. Southeastern Geology, vol. 23, p. 117- 122. 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. 8.6.0 based on Allmendinger et al. (201 3) and Cardozo and Allmendinger (201 3). Equal Area Schmidt Net Projection of Contoured Poles to Primary Bedding and Layering Contour Interval =2 sigma; N=73 Equal Area Schmidt Net Projection of Contoured Poles to Foliation and Cleavage Contour Interval = 2 sigma; N=256 Unidirectional Rose Diagram of Joints N = 178 Outer Circle = 10% Mean vector = 337.1 degrees ± 14.9 degrees; Max value = 10.11236% between 151 degrees and 160 degrees TRAVERSE MAP Hillshade derived from a 20 foot LiDAR digital elevation model. Red and blue lines show paths of field traverses. by car by foot 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. Geologic data collected in July 2015 through May 2016 and June 2017 through May 2018. Acknowledgements: Field assistance in January through March 2016 provided by Randy Bechtel and members of the Energy Group - Oil and Gas Program: Ann Shields, Ryan Channell, Katherine Marciniak, and WaltT. Haven. Geologic Map of the Chatham County portion of the Coleridge 7.5-Minute Quadrangle, Chatham and Randolph Counties, North Carolina. Open File Report 2018-03