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QalQal
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Qal
PPrgd
PPrgj
PPfg
ZPhbg
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PPrgfm
PPfg
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PPg
PPg
PPrgfm
ZPbms
PPrgk
PPg
ZPbms
PPg
PPg
PPg
PPg
ZPbms
PPrgk
PPg
PPg
PPg
ZPbms
ZPhbg
ZPbms
ZPbms
ZPbms
PPgd
ZPbms
ZPhbg
PPg
ZPbms
ZPhbg
ZPhbg
ZPhbg
PPg
ZPhbg
ZPbms
PPgd
ZPhbg
ZPbms
ZPhbg
ZPum
ZPum
ZPum
PPrgj
PPrgj
PPrgd
PPrgd
PPrgd
PPrgd
PPrgd
PPwg
PPwg
PPwg
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ZPhbg
ZPhbg
ZPhbg
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ZPgg
PPfg
PPrgfm
PPfg
ZPbms
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78 22' 30"36 22' 30"
78 15'36 15'
78 15'36 22' 30"
78 22' 30"36 15'
FAUL
T (?)
LAKE
GORD
ON
A'
qrx
qrx
qrx
qrx
qrx
Jd
JdJd
A
A A'
sea level
-2800'
sea level
-2800'
Lake Gordonfault zone
StewartFarm Rd.
S. CokesburyRd.
StewartRd.
Jones ChapelRd.
ShephardRd.Satterwhite
Point Rd.Anderson
Cr. US 1 Business/US 158
US 1 BypassBrookston
Rd.Warrenton
Rd. Daniel HarrisRd.I 85
Jd2PPg
PPwgPPwg
ZPgg
ZPgg
PPfg ZPbms
ZPhbg
ZPhbgPPrgfm
measurements in feet - no vertical exaggeration
Produced by the United States Geological Survey.Altered by the North Carolina Geological Survey for use with map.
Be d roc k Ge ologic Map of the Vic ksboro 7.5-m inute Q uad rangle ,Warre n, Vanc e and Franklin Countie s, North Carolina
By Edward F. Stoddard and Randy Bechtel
2020Digital representation by Michael A. Medina and Philip J. Bradley
Bedrock Geologic Map of the Vicksboro 7.5-minute Quadrangle, Open File Report 2020-02North Carolina Department of Environmental QualityEnergy, Mineral and Land ResourcesBrian L. Wrenn, Division DirectorKenneth B. Taylor, State Geologist
North Carolina Geological SurveyOpen File Report 2020-02
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.This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program under StateMap award numbers G16AC00288, 2016; G17AC00264, 2017;G18AC00205, 2018; and G19AC00235, 2019.This map and explanatory information is submitted for publication with the understanding that the United States Government is authorized to reproduce and distribute reprints forgovernmental 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.Ac knowle d gm e nts:We are thankful for Jim Chapman, Tyler Clark, Brandon Peach, Aaron Rice, Andy Wales, and Nathan Welch, who assisted with fieldwork. We also thank PhilBradley and Aaron Rice for assistance with office work and logistics. Discussions concerning the geology of the region with Aaron Rice, Brandon Peach, Jack Nolan, Phil Bradley,Mark Carter, Robby Morrow, Patrick Finnerty and Dave Blake were invaluable. Thanks also to Steve Stadelman, who introduced us to the area and has independently undertaken astudy of surficial deposits in the region. In addition, we thank all the landowners who graciously allowed access to their property, especially Herman Collier and the folks at the NorthCarolina Motorsports Park.
REFERENCESAllm e nd inge r, R. W., Card ozo, N. C., and Fishe r, D., 2013,Structural Geology Algorithms: Vectors and Tensors: Cambridge, England, Cambridge University Press, 289 pp.Blake , D. E., and Stod d ard , E. F., 2016,Bedrock geologic map of the Henderson 7.5-minute quadrangle, Vance County, North Carolina: North Carolina Geological Survey Open-File Report2016-17, scale 1:24,000, in color. Card ozo, N., and Allm e nd inge r, 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.Farrar, S.S., 1985a,Stratigraphy of the northeastern North Carolina Piedmont: Southeastern Geology, v. 25, p. 159-183.Farrar, S.S., 1985b,Tectonic evolution of the easternmost Piedmont, North Carolina: Geological Society of America Bulletin, v. 96, p. 362-380.Finne rty, P., Nolan, J. T., Ric e , A. K., Pe ac h, B. T., Blake , D. E., LaMaskin, T. A., and Barbe au, D. L., 2019,Status of geologic mapping and LA-ICP-MS U-Pb zircon geochronology from theRaleigh terrane in the North Carolina eastern Piedmont: Geological Society of America Abstracts with Programs, v. 51, No. 3.Hibbard , J. P., Stod d ard , E. F., Se c or, D. T., and De nnis, A. J., 2002,The Carolina Zone: Overview of Neoproterozoic to Early Paleozoic peri-Gondwanan terranes along the eastern flank ofthe southern Appalachians: Earth Science Reviews, v. 57, p. 299-339.Mc Danie l, R. D., 1980,Geologic map of Region K: North Carolina Department of Natural Resources and Community Development, Geological Survey Section, Open File Map NCGS 80-2[scale 1:100,000].Parke r, J. M., III, 1968,Structure of easternmost North Carolina Piedmont: Southeastern Geology, v. 9, p. 117-131.Sac ks, P.E., 1996a,Geologic map of the Bracey 7.5-minute quadrangle, Mecklenburg County, Virginia, and Warren County, North Carolina: U.S. Geological Survey, Miscellaneous FieldStudies Map MF-2285, scale 1:24,000.Sac ks, P.E., 1996b,Geologic map of the South Hill SE 7.5-minute quadrangle, Mecklenburg and Brunswick Counties, Virginia, and Warren County, North Carolina: U.S. Geological Survey,Miscellaneous Field Studies Map MF-2286, scale 1:24,000.Sac ks, P.E., 1996c ,Geologic map of the Gasburg 7.5-minute quadrangle, Brunswick County, Virginia, and Warren, Northampton, and Halifax Counties, North Carolina: U.S. Geological Survey,Miscellaneous Field Studies Map MF-2287, scale 1:24,000.Sac ks, P.E., 1996d ,Geologic map of the Valentines 7.5-minute quadrangle, Brunswick and Greensville Counties, Virginia, and Northampton, and Halifax Counties, North Carolina: U.S.Geological Survey, Miscellaneous Field Studies Map MF-2288, scale 1:24,000.Spe e r, J.A., 1994,Nature of the Rolesville Batholith, North Carolina, in Stoddard, E.F. and Blake, D.E., eds., Geology and Field Trip Guide, Western Flank of the Raleigh Metamorphic Belt,North Carolina, Carolina Geological Society Guidebook for 1994 Annual Meeting, p. 57-62.Stod d ard , E. F., 2010,Bedrock geologic map of the Ingleside 7.5-minute quadrangle, Franklin and Vance Counties, North Carolina: North Carolina Geological Survey Open-File Report 2010-05, scale 1:24,000, in color.Stod d ard , E. F., Blake , D. E., and Buford , C. L., 2016,Bedrock geologic map of the Middleburg 7.5-minute quadrangle, Vance and Warren Counties, North Carolina: North CarolinaGeological Survey Open-File Report 2016-04, scale 1:24,000, in color.
Neop
rotero
zoic-
Mid P
aleoz
oicMi
d to L
atePa
leozo
icMe
sozo
icQu
aterna
ry
Late Pale ozoic Intrusive s
Rale igh Te rrane
Hyd rothe rm al Unit
CORRELATIONOF MAP UNITS
metamorphosed sedimentary and igneous rocks(stratigraphic relations uncertain)
qrx
Jd2
PPrgfm
PPrgj
PPgd
Jd
Qal
PPg PPfg
PPrgk
ZPgg
PPwg
ZPum
PPrgd
ZPhbg
ZPbms
This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program
CONTACTS, FAULTS, AND OTHER FEATURES
PLANAR FEATURES
LINEAR FEATURES
TRAVERSE MAPHillshade derived from a 20 foot LiDAR digital elevation model.
Red lines show paths of field traverses. All roads traversed by car.
EXPLANATION OF MAP SYMBOLS
Strike and dip of crenulation cleavage
Strike and dip of inclined undifferentiatedshear strain foliation(multiple observations at one location)
Strike and dip of inclined regional foliation
Strike of vertical regional foliation
Strike and dip of inclined regional foliation(multiple observations at one location)
Strike of vertical regional foliation(multiple observations at one location)
7770
3225
64
18
Strike and dip of inclined dike
Strike and dip of inclined dike(multiple observations at one location)
Strike of vertical dike(multiple observations at one location)
Strike and dip of gneissic layering
Strike of vertical gneissic layering
Strike and dip of gneissic layering(multiple observations at one location)
Strike of vertical gneissic layering(multiple observations at one location)
6077
Strike of vertical dike
5270
65
63
Strike and dip of inclined quartz vein
Strike of vertical quartz vein
Strike and dip of inclined joint/fracture surface
Strike and dip of inclined joint/fracture surface(multiple observations at one location)
Strike of vertical joint surface(multiple observations at one location)
Strike of vertical joint surface
7080
Strike and dip of compositional layering73
78
85
Bearing and plunge ofcrenulation lineation
Bearing and plunge of mineralor aggregate lineation
Bearing and plunge of pencil lineation
50
47
Bearing and plunge of lineation -type undetermined
11
Bearing and plunge ofmesoscale fold hinge
36
Qal
PPfg
PPg
ZPbms
ZPhbg
ZPgg
qrx
Jd
N.C.
DESCRIPTION OF MAP UNITSSedimentary UnitQ al - Q uate rnary alluvium :Unconsolidated, poorly sorted and poorly stratified tan to light gray stream deposits of gravel, sand, silt,and clay.Hydrothermal Unitq rx -- Q uartz c atac lasite :Sizable accumulations of milky and/or smoky quartz, commonly with vuggy crystals. Locally includesbreccia with angular fragments of granitoid rock and having a quartz matrix. Possibly related to quartz mineralization along brittlefracture zones or faults. Based on such occurrences, several fault segments are inferred, having typical trends NNW and E-W.Yellow squares indicate isolated outcrop or major float occurrence. Considered to be Mesozoic in age.Intrusive UnitsJd – Olivine d iabase d ike s: Steeply dipping to vertical, gray to blue-black, fine to medium crystalline, magnetite-bearing olivinediabase. Locally plagioclase porphyritic. Spheroidal weathering has produced ovoid to round residual cobbles and boulders.Jd 2 – Two-pyroxe ne d iabase d ike : Steeply dipping to vertical, gray to bluish black, medium crystalline and typically plagioclaseporphyritic, olivine-free augite + pigeonite diabase commonly containing quartz and/or alkali feldspar granophyre. Magnetite bearing.Occurs in a single extensive dike in the northwest corner of the quadrangle, where it can be easily traced along the upper (southern)stretches of Anderson Creek northward into the Middleburg Quadrangle. May be traced toward the south across Interstate Route 85.Enters the Henderson Quadrangle as it crosses US Route 1 Bypass. Spheroidal weathering has produced ovoid to round residualcobbles and boulders. This dike is evident on aeromagnetic maps.
PPg – Granite :Medium-grained, equigranular to weakly porphyritic white, pink, orange or buff biotite ± muscovite granite (CI=8-15).Includes fine to medium-grained, non-porphyritic, locally foliated white mica ± garnet ± biotite leucogranite (CI less than 5), and raregranodiorite (CI=15-20). Pegmatite dikes common. Occurs in numerous pods in the northern half of the Vicksboro quad, typicallysurrounded by more strongly deformed and/or metamorphosed rocks.PPgd - Gabbro-d iorite :Dark gray, mesocratic, medium to coarse-grained hornblende-biotite diorite and gabbro and their weaklymetamorphosed equivalents. Uralitized augite is common. Also contains magnetite and typically titanite. Best exposed along easternend of Club Pond in the western Vicksboro quad; also occurs along a small creek in the northeastern part of the quad east of DeerfieldFarms Rd. CI=40-60.Wise PlutonPPwg – Eq uigranular biotite granite :Leucocratic (CI less than 15), orange-tan to gray-tan, pink or salmon and white, medium tocoarse-grained, generally equigranular but locally weakly porphyritic biotite ± epidote granite and sparse weakly porphyritic biotite ±white mica ± garnet leucogranite. Locally crosscuts foliated biotite granite. Locally contains enclaves of hornblende biotite gneiss(ZPhbg). Interpreted as belonging to the Wise pluton. Occurs along the eastern edge of the Vicksboro quad, mainly in the north.May be e q uivale nt to PPrgd of the Ingle sid e and Louisburg Q uad rangle s,and/or to the Rolesville main phase of Speer (1994).Rolesville BatholithPPrgk – Le uc ogranite :Medium-grained, generally equigranular white, pink, orange or buff biotite +/- muscovite leucogranite andgranite, locally with garnet. Garnet commonly present as trapezohedral crystals. Occurs in the south-central Vicksboro quad in theupper stretches of Buffalo Creek where it is associated with and may contain xenoliths of gneiss and schist. Commonly cut bypegmatite dikes locally having smoky quartz. Also occurs near the center of the quad, along a tributary of Weaver Creek. CI = 2-8.PPrgd – Porphyritic biotite granite :Fine to coarse-grained, but primarily medium-grained, equigranular to moderately porphyritic(very rarely megacrystic), rarely foliated, pink or salmon and white biotite + muscovite monzogranite. Commonly has an almostidiomorphic fabric with well-formed alkali feldspar and plagioclase grains. Contains common biotite schlieren and local biotite crystalclots. Pegmatite dikes and pods are extremely common. Unit also contains relatively common xenoliths of gneiss and schist. Lesscommonly contains autoliths of fine granodiorite or tonalite and may display primary igneous layering between biotite-rich and biotite-poor phases. CI = 5-12. Weathered surfaces are commonly nubbly, friable and/or cavernous. Judged to be equivalent to theRolesville main phase of Speer (1994), but commonly lacks muscovite. Occurs mainly in the southern and southeastern quarter of theVicksboro quad.PPrgj – Gne issic biotite granite :Heterogeneous granitoid unit typically consisting of streaky, gneissic, or layered biotite granitoidand biotite granitoid gneiss. Includes granite, leucogranite, and granodiorite and their gneissic counterparts. May contain biotite orfeldspar foliation. Commonly contains magnetite. In southwestern Vicksboro quad, notably along Martin and Gills Little Mill Creeks.Rarely mylonitic.PPrgfm – Foliate d to m ylonitic granite and granitoid orthogne iss:Leucocratic (CI less than 5-15) medium to coarse grained, pinkor salmon and white, commonly porphyritic or porphyroclastic biotite granite, biotite leucogranite, and biotite granitoid orthogneiss.Strongly foliated, protomylonitic, or mylonitic in most exposures. K-feldspar porphyroclasts with local tails indicating a dextral shearsense. Pegmatite and aplite dikes and sills common and may be deformed. Includes some minor undeformed granite. Also includesminor biotite schlieren and biotite and biotite-hornblende gneiss enclaves. In northwestern Vicksboro quad and along the westernedge. Eq uivale nt to Pg1 of Mid d le burg q uad and PPrgm and RRrgf of He nd e rson q uad .Lies between the Nutbush Creek andLake Gordon mylonite zones.Rolesville Batholith or Buggs Island Pluton (?)PPfg – Foliate d granitic roc ks:Medium to coarsely crystalline, locally megacrystic, porphyroclastic, strongly foliated tan-gray toblue-gray, leucocratic to mesocratic, biotite + white mica granite and white mica ± biotite ± garnet leucogranite. Commonlyprotomylonitic to mylonitic and ultramylonitic. Commonly porphyroclastic. Includes mylonitized pegmatitic to coarsely crystalline,porphyroclastic white mica ± biotite + quartz + feldspar metagranitoid sills, presenting a migmatitic appearance. Also includesgranitoid orthogneiss and numerous enclaves of biotite + hornblende gneiss, notably at the Greystone Quarry. Lies at least partlywithin the Lake Gordon mylonite zone. Eq uivale nt to Pg1, Pg2 and Pg3 of the Mid d le burg Q uad rangle .Metamorphic UnitsRaleigh TerraneZPbm s - White m ic a biotite sc hist:Medium-fine to coarse crystalline, gray-tan to silvery, strongly foliated white mica + biotite schistwith or without garnet, and biotite + white mica + garnet + sillimanite schist. Sillimanite and garnet may be overgrown by white mica.Commonly feldspathic. Locally phyllonitic to mylonitic with feldspar porphyroclasts. Locally contains chlorite. May be intruded bypegmatitic to coarsely crystalline, porphyroclastic white mica ± biotite + quartz + feldspar gneissic metagranitoid sills that are locallymigmatitic. Locally includes small bodies of leucogranite. Eq uivale nt to ZPwm s of the Mid d le burg Q uad rangle .ZPgg – Granitoid gne iss:Medium to dark gray, fine to medium grained, moderately to well foliated biotite-quartz-plagioclase ±alkalifeldspar gneiss and schist. Varies from unlayered biotite granitoid gneiss to variably layered biotite gneiss to schistose biotite gneissand rarely biotite schist. Layers are typically discontinuous. Locally protomylonitic, mylonitic, or ultramylonitic. Locally carries garnet,epidote, or sulfide minerals. Locally associated with dikes and/or sills of pegmatite and/or leucogranite. Also occurs as xenolithswithin granitoid bodies. Eq uivale nt to ZPfg of the Mid d le burg Q uad rangle .ZPhbg – Hornble nd e biotite gne iss: Leucocratic to mesocratic (CI~20-45), black-gray to blue-gray, medium grained toporphyroclastic gneiss. More mafic occurrences locally contain clinopyroxene and/or epidote; pyroxene-rich rocks may be granulites.Biotite and/or hornblende define a foliation associated with mm-scale plagioclase and quartz compositional layers and, locally, largerplagioclase porphyroclasts. Weakly to strongly layered. Includes rare fine-grained calcsilicate rock or hornfels consisting ofamphibole + quartz + sulfides ± clinopyroxene and/or biotite. Also includes fine to medium-grained, poorly to moderately well-layeredamphibolite and amphibolite gneiss. Includes layers and other domains of biotite granitoid gneiss and small unmapped bodies ofcross-cutting granite and leucogranite. Dikes and sills of pegmatite are profuse. Local grain size variations in part due to myloniticoverprint. Eq uivale nt to ZPpg of the Mid d le burg Q uad rangle .ZPum - Me taultram afic roc ks:Hypermelanocratic to melanocratic (CI greater than 65), green to black-green interlayers and pods ofmassive, coarse-grained talc ± actinolite schist and, locally, medium-grained metagabbro. Occurs as enclaves in ZPhbg.
INTRODUCTION AND PREVIOUS MAPPINGThe Vicksboro 7.5-minute quadrangle lies at the mutual intersection of Warren, Franklin, and Vance Counties, North Carolina. The eastern outskirtsof the city of Henderson, NC, county seat of Vance County, are along the western edge of the Vicksboro Quadrangle. Interstate Highway I-85 andUS Highway 1 lie in the northwestern corner of the quadrangle. These highways run between Richmond, VA, and the Raleigh-Durham region of NC.NC Highway 39 lies in the southwestern part of the quadrangle, running northwest from Louisburg in Franklin County to Henderson. US Highway401 crosses the extreme southeastern corner of the quadrangle, running northeast from Louisburg to Warrenton. The northern part of the area istraversed from west to east by SR 1001, which is known as Warrenton Road in Vance County, and as Dr. Martin Luther King, Jr. Blvd. in WarrenCounty.In addition to a portion of the city of Henderson, the area contains the communities of Cokesbury, Gillburg, Faulkner Crossroads, AdcockCrossroads, Weldons Mill, Brookston, and Greystone in Vance County, and in Warren County, the populated places of Vicksboro and Axtell. It is adominantly agricultural area, with several large dairy farms. A large crushed-stone operation, the Greystone Quarry, is operated by Vulcan Materialsat the intersection of US Route 1 and Interstate 85 at the northwestern corner of the map area.Several Vance County public schools lie within the Vicksboro Quadrangle, including Aycock, Carver, and Clarke Elementary Schools, Vance CountyMiddle School and Vance County High School. Aycock Recreation Center and Fox Pond Park, both operated by the City of Henderson, sit near thewestern edge of the quadrangle, and the North Carolina Motorsports Park lies in southwestern Warren County within the quadrangle.The area is drained by the upper stretches and by tributaries of Fishing, Shocco, and Sandy Creeks, which themselves are major tributaries of theTar River. Anderson Creek flows northward into Kerr Lake from its source in the northwest corner of the area. Total relief is about 260 feet, withelevations of slightly less than 270 feet above sea level where Sandy Creek leaves the southern edge of the Vicksboro Quadrangle in the southeast,to over 530 feet above sea level between Greystone and Adcock Crossroads in the northwestern part of the area.The map area is underlain mainly by a diverse array of granitoid rocks, gneiss, and schist. Many of the rocks are highly deformed, and the westernhalf of the area lies along two zones of intense ductile shear attributed to the Lake Gordon and Nutbush Creek faults. The granitoid rocks in thesouthern part of the map belong to the late Paleozoic (Alleghanian) Rolesville batholith. Granite along the eastern edge of the map belongs to theundeformed and presumed late Paleozoic Wise pluton. The granites are intrusive into gneisses and schists of the Raleigh terrane, interpreted as aninfrastructural component of a Neoproterozoic volcanic arc (Hibbard and others, 2002). This understanding of the metamorphic country rocks in theregion has been brought into question as a result of recent geochronological studies that have yielded mid-Paleozoic zircon ages (e.g. Finnerty andothers, 2019).Prior to this investigation, little geologic mapping had been undertaken in the quadrangle, although it has been included in some regional andreconnaissance studies. Parker (1968) defined the structural framework of the region. McDaniel (1980) mapped a multi-county region, includingWarren and Vance Counties, at a scale of 1:100,000. Farrar (1985a, b) mapped the entire eastern Piedmont of North Carolina, defined map units forthe region, and proposed a model for the tectonic evolution of the region. Sacks (1996a, b, c, d) mapped a strip of four 7.5-minute quadranglesalong the Virginia-North Carolina border, along strike to the north-northeast.Adjacent to the field area, 1:24,000-scale mapping has been done for the Middleburg Quadrangle to the north (Stoddard and others, 2016).Mapping of the Afton Quadrangle to the east is ongoing (Blake, Peach, Morrow, and Nolan, in progress). To the south and west of the VicksboroQuadrangle, the Ingleside (Stoddard, 2010) and Henderson (Blake and Stoddard, 2016) Quadrangles have been mapped at 1:24,000.
PPrgk
PPrgd
PPrgj
PPrgfm
Jd2 Eq ual-Are a Sc hm id t Ne t Proje c tionsand Rose Diagram
Plots and calculations created using Stereonet v. 8.6.0 based onAllmendinger et al. (2013) and Cardozo and Allmendinger (2013).
Unidirectional Rose Diagram of Joints N = 204Outer Circle = 10%
Mean vector = 92 degrees
Equal-Area Schmidt Net Projectionof Contoured Poles to Foliation
and SchistosityContour Interval = 2 sigma N = 315
Equal-Area Schmidt Net Projection ofContoured Poles to Compositional and Gneissic Layering
Contour Interval = 2 sigma N = 294
Equal-Area Schmidt Net Projection ofFold Hinges (black circles) and Lineations(Mineral, Pencil and other) (blue squares)
Fold Hinges N = 15Lineations N = 22
ZPum
PPgd
by footby car
PPwg
concealed contactinferred contact
observation station location
quartz cataclasite zoneconcealed
quartz cataclasite zoneinferred
inferred ductile strike-slip faultconcealed ductile strike-slip faultQuaternary alluvium contact
diabase station location
diabase dike, location known
bull quartz veinstation location
quartz cataclasitestation location abandoned quarry
In cross section, for ductile strike-slip faults,the circle with an X indicates movement away from the observer,the circle with a dot indicates movement towards the observer.
cross section lineA A'
crushed stone quarry - active
strike and dip of brittle fault
Strike of vertical compositional layering
Strike of vertical undifferentiatedshear strain foliation(multiple observations at one location)
Strike and dip of vertical undifferentiatedshear strain foliation
41
Strike and dip of inclined schistosity
Strike and dip of inclined schistosity(multiple observations at one location)
7080
85
48
diabase dike, location inferred
