Map Unit Properties Table Colored rows indicate units mapped within Appomattox Court House National Historical Park.

Unit Name Erosion Age Features and Description Suitability for Development Hazards Cultural Resources Karst Mineral Occurrence Habitat Geologic Significance (Symbol) Resistance

Suitable for most development unless Unit typically appears as irregular masses, but may also occur as high fractured, or weathered discrete dikes and sills. In Appomattox area, unit is linear. Diabase Unit often underlies (friable), in which case there is a Plagioclase, Unit is time-correlative is an intrusive igneous rock with fine- to coarsely-crystalline, ridges that factored Unit may support Diabase Very high if potential for shrink and swell clays. Rockfall potential for this clinopyroxene. with Mesozoic extension subaphanitic or porphyritic with aphanitic margins. Crystalline into troop movements None. localized plant species (Jd) unweathered. Unweathered rocks of this unit are unit if exposed on slope. Unit may be used for events across the eastern textures include dark-gray mosaic of long thin plagioclase crystals throughout the Civil changes.

LOWER nearly impossible to modify or move decorative stone. United States.

JURASSIC and clinopyroxene. Some masses contain olivine or bronzite, War. without blasting and heavy whereas others are granophyric. equipment.

Deformed metamorphic rock. Textures include protomylonite, Unit contains deformation , ultramylonite, and cataclastic. Myriad lithologies Units are heavily deformed and fabrics from Paleozoic present, depending on the nature of the parent rock, and degree foliated, containing small lenses of contractional events and nature of deformation. Most outcrops contain belts of Moderate to low Deformation bands Deformed nature of many rock types. This variability may superimposed on Late mylonite and anastomosing around lenses of less- depending on between large blocks may unit creates localized Mylonite render the units unstable for heavy Precambrian extensional deformed or undeformed country rock. Typically, mylonitic and degree of cause them to be None documented. None. None documented. permeability changes (My) development. The high mica content and locally contractional cataclastic rocks are gradational into less deformed or deformation and susceptible to rockfall and that may affect of this unit gives it the potential for fabrics. Mesozoic undeformed adjacent rocks, and contacts are approximate or weathering. mass wasting on slopes. vegetation patterns. MESOZOIC severe erosion and sedimentation extensional reactivation arbitrary. Most belts of mylonite represent zones with control may be required. overprints earlier fabrics multiple deformational events throughout the Paleozoic and along local faults. Mesozoic locally.

Lenses of resistant rocks in

Avoid highly schistose layers as well schistose layers may be Mica schist contains 1- to 2-mm (0.04–0.08 in) garnet as areas of intense preferential susceptible to mass Biotite, garnet, Porphyroblastic porphyroblasts in an anastomosing, greenish-black biotite-rich, Garnets provide Unit has elongate positive compositional weathering (along wasting. Severe erosion and Some dissolution is muscovite, quartz, Unit weathers to garnet-biotite schistose matrix. Many exposures show complex microstructures abrasive material and magnetic and radiometric Moderate. ). High mica contents render sedimentation potential possible in local plagioclase, magnetite, produce iron- and schist recording many phases of deformation. Locally, unit contains may have been objects anomalies as an enigmatic the unit susceptible to severe erosion exists if unit is exposed due marbles. kyanite, and calcite. calcium-rich soils. (Oas) quartz-rich muscovite schist and thin interbeds of calcareous mica of early trade. geophysical signature. and causes increased sediment load to high mica content. Some marble present. schist and marble. ORDOVICIAN in regional streams. Potential for shrink and swell clay issues.

Units are suitable for most N Gneiss ranges from light-colored to ~equal amounts of light and development unless local blocks Avoid units exposed and Quartz, potassium Western portions of this Lineated biotite dark minerals, with medium- to coarse-grained textures. and/or plagioclase groundmass are Moderate to undercut on slopes due to feldspar, plagioclase, unit coincide with a strong granite gneiss fabrics are strong and some areas are locally porphyritic. Unit altered and weathered to saprolite, None documented. None. None documented. high. potential spalling and mass biotite, muscovite, positive radiometric (Lgn) comprises more than one intrusive body and interlayers with rendering the unit friable. Unit may wasting hazards. garnet. anomaly. Cambrian-age rocks associated with volcanic processes. be deeply weathered and unstable for

ORDOVICIA deep excavated cuts.

Myriad lithologies include light-gray to grayish-pink dacitic metatuff, very-light-gray quartz-rich muscovite and biotite- Avoid units exposed and

muscovite schist, and medium-gray biotite-muscovite gneiss. undercut on slopes due to Felsic metatuff, Metatuff is very-fine-grained to aphanitic, thin-bedded and may potential mass wasting Unit is exposed in the Weathers to acidic, Heterogeneity of units may render Quartz, plagioclase, Unit records Cambrian mica schist, and contain plagioclase phenocrysts bounded in part or totally by well- hazards. Severe erosion park, and outcrops orange, saprolitic Moderate. them unstable locally for foundation, None. muscovite, biotite, volcanic activity and gneiss defined crystal faces. Distinctive pinstripe pattern characterizes and sedimentation may have Civil War regolith with low road, and facilities development. epidote, magnetite. mélange accretion. (Cfvs) local schists. Gneissic units are have characteristic salt-and-pepper potential exists if unit is significance. permeability.

CAMBRIAN appearance and are fine-grained. Some subordinate amounts of exposed because of high greenstone metabasalt and amphibole gneiss are interlayered mica content. locally.

Intersections of bedding and flow Greenstone is dark- to dusky-green, with schistose textures Lenses of resistant rocks in Units weather to cleavages in greenstones as well as Actinolite, chlorite, including actinolite-chlorite mineralogies with segregations of the schistose layers may be Unit is exposed in the produce calcium- and Greenstone or heavily altered zones may be points epidote, quartz, Unit records subaqueous minerals epidote and quartz. Greenstone interlayers with susceptible to block and park, and outcrops magnesium-rich amphibole gneiss Moderate. of weakness in units. Due to high None. hornblende, basaltic extrusion during hornblende-plagioclase gneiss and subordinate amounts of dacitic rockfall. Abundant shrink may have Civil War orangish clayey soils, (Cmvs) shrink and swell clay potential, avoid plagioclase, muscovite, the Cambrian. metatuff, quartz-muscovite schist, and fine-grained salt-and- and swell clay potential significance. well-suited for development of buildings and septic biotite. CAMBRIAN pepper biotite-muscovite gneiss. exists for this unit. growing tobacco. fields on this unit.

APCO Geologic Resources Inventory Report 16

Unit Name Erosion Age Features and Description Suitability for Development Hazards Cultural Resources Karst Mineral Occurrence Habitat Geologic Significance (Symbol) Resistance

Quartz, plagioclase, Unit has a positive- Granite is light greenish gray with pink bands present in irregular Suitable for most development unless potassium feldspar, Deformed nature of Coarse-grained radiometric / negative- masses. Textures range from medium to coarse grained. High to highly weathered and/or fractured. May be susceptible to mass biotite, muscovite, unit creates localized Melrose granite specimens may have magnetic geophysical Compositions vary between quartz monzonite and quartz diorite. moderate where Avoid weathered areas for basements wasting if exposed on None. chlorite, epidote, permeability changes (Cm) attracted early trade signature and a radiometric Near the Brookneal zone, deformation textures in the deformed. and foundations due to potential slope. titanite, garnet, that may affect interest. (Uranium-Lead) age date granite grade from protomylonite to mylonite to ultramylonite. radon problem. magnetite-ilmenite, vegetation patterns. CAMBRIAN of 515 million years. calcite, zircon.

Avoid weathered areas of rhyolite May be susceptible to mass composition for basements and wasting if exposed on Cryptocrystalline Quartz, perthitic Light-colored igneous rock. Foliated unit ranges in composition foundations due to potential radon Unit weathers to Foliated felsite slopes. Severe erosion and metarhyolite was a microcline, muscovite, Unit records Cambrian-age from rhyolite to dacite. In outcrop, unit appears light gray to white Moderately high. problem. Unit may weather to None. produce potassium- (Cfv) sedimentation potential prized tool material biotite. Large beta-form volcanism. with medium-grained textures. saprolite and would be severely rich soils. exists if unit is exposed, for American Indians. quartz phenocrysts. susceptible to erosion due to high CAMBRIAN due to high mica content. mica content.

Preferential weathering of Unit includes widely Suitable for most development unless less resistant layers may recognized Blackwater Amphibolite, highly weathered and/or fractured. increase likelihood of In outcrop, unit appears black to moderate olive brown. Coarse-grained Creek Gneiss and Catawba hornblende- Development of buildings and other spalling when unit is Hornblende, tremolite- Unit weathers to Lineations and foliations record pervasive deformation with specimens may have Creek amphibolite member biotite gneiss and Moderately high. infrastructure may be compromised exposed on a slope. None. actinolite, oligoclase, produce “sweet” textures ranging from medium to coarse grained. Stringers of attracted early trade of Hyco Formation, schist due to the presence of abundant Abundant shrink and swell biotite, epidote, garnet. calcium-rich soils. quartz and epidote are relatively common. interest. hornblende gneiss, and (Cmv) shrink and swell clays associated with clays associated with this CAMBRIAN dominantly mafic- weathered portions of this unit. unit can cause widespread composition units. instability.

– Unit is susceptible to mass Unit appears light and dark gray with medium-grained textures Unit is suitable for most development wasting when exposed on Unit records and fine laminations. Other interlayered rock types include unless highly heterogeneous layers Calcite, quartz, biotite, slopes and undercut by Karst dissolution is Unit weathers to accretion along continental Banded marble calcareous gneiss and schist. Locally thick to thin beds of marble are present, or beds are heavily muscovite, plagioclase, Moderate. local rivers. Pyrite and None documented. possible in produce calcium-rich margins and includes the (CZac) alternate with graphitic phyllite and mica schist, with fractured. Avoid areas with high pyrite, magnetite- LATE other sulfide minerals calcareous units. soils. Arch Marble and Archer compositions ranging from impure marble to calcareous carbonate contents for wastewater ilmenite. could produce acid Creek Formation. CAMBRIAN metagraywacke. treatment or septic systems. drainage if disturbed. PROTEROZOIC

May be susceptible to mass Avoid areas of intense preferential Quartz, potassium

– wasting if exposed on Units record multiple Myriad rock types include: medium to light gray laminated quartz- compositional weathering (along feldspar, plagioclase, slope; talc and weathered deformation events, and feldspar-rich to calcareous gneiss with thin mica schist foliation). Suitable for most biotite, muscovite, areas may increase including uplift along the Feldspathic partings; white and gray fine- to coarse-grained generally development unless highly Some dissolution of calcite, epidote, titanite, likelihood of sliding. Bowens Creek fault; they metagraywacke laminated marble; gray to greenish gray fine-grained graphitic Moderate. weathered and/or fractured, None documented. laminated marble is magnetite-ilmenite, None documented. Graphitic schists may were previously mapped as LATE (CZmy) mica schist and quartzite; light gray medium- to fine-grained mica especially along talc-rich layers and possible. graphite, chlorite, contain high sulfide the Evington Group and schist; massive quartzite and micaceous blue quartz granule boundaries. Actinolite schists may albite, garnet, kyanite, CAMBRIAN assemblages that could are continuous with the metasandstone; and dark greenish black actinolite schist. weather to produce shrink and swell tremolite, talc,

PROTEROZOIC produce acid drainage if Lynchburg Group. clays. actinolite, dolomite. disturbed.

– Quartz, muscovite, Unit contains aluminosilicate-mica schist interlayered with other Unit has characteristic High degree of biotite, garnet, metamorphic rocks such as garnet-rich biotite gneiss, calcsilicate Unit has highly heterogeneous Garnets provide “curly maple” magnetic deformation renders unit staurolite, magnetite, granofels, amphibolite, rare white marble, and calc-quartzite lithology and is heavily deformed, abrasive material and contour map patterns due Mostly moderate unstable on slopes; may be ilmenite, rutile, Deformed nature of lenses. Schist is light to medium gray, with textures ranging from rendering it rather weak for heavy may have been objects to isolated concentrations Fork Mountain depending on prone to mass wasting. Rare white marbles paragonite, plagioclase, unit creates localized fine to medium grained. Units underwent multiple episodes of development. Amphibolite layers of early trade. of highly magnetic Formation degree of Shrink and swell clays may be prone to sillimanite, potassium permeability changes deformation and were metamorphosed with locally present may weather to produce shrink and Unit is exposed in the minerals. Many mineral (CZfm) alteration and associated with weathering dissolution. feldspar, tourmaline, that may affect porphyroblasts. Metamorphic and deformation textures include swell clays that may pose problems park, and outcrops assemblages record deformation. of amphibolites in this unit hornblende, epidote, vegetation patterns. CAMBRIAN schistosity, multiple cleavages, and partly retrograded for building foundations and other may have Civil War prograde and retrograde can cause widespread kyanite, chlorite, porphyroblasts of garnet and aluminosilicate. Some brittle infrastructure. significance. metamorphic events in the instability. chloritoid, andalusite, deformation is recorded in polymictic breccias. area. LATE P ROTEROZOIC corundum, spinel.

APCO Geologic Resources Inventory Report 17

Unit Name Erosion Age Features and Description Suitability for Development Hazards Cultural Resources Karst Mineral Occurrence Habitat Geologic Significance (Symbol) Resistance

Metagraywackes include quartz-rich chlorite or biotite schists,

– and contain very fine to coarse granules of blue quartz. Shearing Locally, polydeformed transposes primary graded laminations into elongate lozenge Unit weathers to quartz-rich mica schists are shapes that give the rock a distinctive pinstriped appearance in May be susceptible to mass Quartz, albite, epidote, produce relatively Schistose, mylonitic, and highly lithologically weathered surfaces that are perpendicular to schistosity. Locally, a wasting if exposed on chlorite, muscovite, impermeable acidic, Metagraywacke, Moderate foliated units should be avoided for indistinguishable from mylonitic fabric and late-stage chevron-shaped folds overprint the slope. Weathered material Blue quartz may have magnetite, chloritoid, orange, saprolitic quartzose schist, depending on heavy development due to inherent schists mapped as Fork earlier schistosity, and rocks in this unit are progressively more (saprolite) is susceptible to been used for early None. calcite, biotite, regolith; quartz-rich and mélange degree of weakness. Heavily deformed and/or deformed from east to west across the outcrop belt. The most severe erosion and trade. staurolite, plagioclase, schists weather to a (CZpm) deformation. weathered areas are also unsuitable (CZfm) in structural blocks deformed rocks contain mylonitic mica schist with quartz-rich sedimentation problems if perthite, tourmaline, light yellowish-gray, CAMBRIAN PROTEROZOIC and unstable in deep excavated cuts. that occur to the west, and sausage-shaped segments. Rock fragments contain dacite tuff, exposed. titanite. sandy, mica-rich may be temporally gabbro, and monocrystalline quartz with zircon and biotite saprolite. ATE correlative. L inclusions. These blocks range from 5 cm to 3 m (2 in to 10 ft) across in outcrop.

APCO Geologic Resources Inventory Report 18