Geologic units in Wilkes county, North Carolina

Additional scientific data in this geographic area

Alligator Back Formation; Gneiss (Late Proterozoic) at surface, covers 40 % of this area

Finely laminated to thin layered; locally contains massive gneiss and micaceous granule conglomerate; includes schist, phyllite, and amphibolite.

Biotite Gneiss and Schist (Cambrian/Late Proterozoic) at surface, covers 16 % of this area

Inequigranular, locally abundant potassic feldspar and garnet; interlayered and gradational with calc-silicate rock, sillimanite-mica schist, mica schist, and amphibolite. Contains small masses of granitic rock.

Alligator Back Formation; Mica schist and phyllite (Late Proterozoic) at surface, covers 13 % of this area

Laminated to thin layered; interlayered with minor biotite-muscovite gneiss and amphibolite.

Metamorphosed Granitic Rock (Ordovician/Cambrian) at surface, covers 8 % of this area

Equigranular to megacrystic, foliated to massive. Includes Toluca Granite.

Migmatitic Granitic Gneiss (Ordovician/Cambrian) at surface, covers 5 % of this area

Foliated to massive, granitic to quartz dioritic; biotite gneiss and amphibolite common.

Quartz Diorite to Granodiorite (Devonian) at surface, covers 5 % of this area

Contains biotite, muscovite, and xenocrysts. Includes Whiteside Mountain, Stone Mountain, Mount Airy, Spruce Pine, and other smaller plutons.

Banded Gneiss (Cambrian/Late Proterozoic) at surface, covers 3 % of this area

Interlayered with calc-silicate rock, metaconglomerate, amphibolite, sillimanite-mica schist, and granitic rock.

Metagraywacke, Amphibolite, and Kyanite Schist (Cambrian/Late Proterozoic) at surface, covers 2 % of this area

Metagraywacke (biotite gneiss) interlayered and gradational with amphibolite and kyanite schist; minor ultramafic and granitic rock.

Mica Schist (Cambrian/Late Proterozoic) at surface, covers 2 % of this area

Garnet, staurolite, kyanite, or sillimanite occur locally; lenses and layers of quartz schist, micaceous quartzite, calc-silicate rock, biotite gneiss, amphibolite, and phyllite.

Fine-grained Biotite Gneiss (Cambrian/Late Proterozoic) at surface, covers 2 % of this area

Strongly foliated; minor layers of amphibolite and muscovite schist.

Biotite Granitic Gneiss (Middle Proterozoic) at surface, covers 1 % of this area

Unconformity; contains paragneiss and granitic to quartz monzonitic orthogneiss; locally schistose and mylonitic. Locally includes tectonic slices, infolded remnants, or recrystallized equivalents of the Grandfather Mountain Formation. Equivalent to the Wilson Creek Gneiss.

Metamorphosed Granitic Rock (Late Proterozoic) at surface, covers 1 % of this area

Massive to foliated, locally mylonitic.

Metagraywacke (Cambrian/Late Proterozoic) at surface, covers 1.0 % of this area

Contains quartz and microcline porphyroblasts.

Alligator Back Formation; Amphibolite (Late Proterozoic) at surface, covers 0.7 % of this area

Equigranular, massive to well foliated, interlayered, rarely discordant, metamorphosed intrusive and extrusive mafic rock; may include metasedimentary rock.

Grandfather Mountain Formation; Felsic metavolcanic rocks and metasedimentary rocks (Late Proterozoic) at surface, covers < 0.1 % of this area

Tentatively correlated with Grandfather Mountain Formation.

Meta-ultramafic Rock (Paleozoic/Late Proterozoic) at surface, covers < 0.1 % of this area

Metamorphosed dunite, local peridotite, serpentinite, soapstone, and other ultramafic rock. Only larger bodies shown.

Meta-ultramafic Rock (Paleozoic/Late Proterozoic) at surface, covers < 0.1 % of this area

Metamorphosed dunite, local peridotite; serpentinite, soapstone, and other altered ultramafic rock. Only larger bodies shown.

Inequigranular Biotite Gneiss (Cambrian/Late Proterozoic) at surface, covers < 0.1 % of this area

Weakly foliated to massive, contains plagioclase megacrysts and, rarely, larger megacrysts of quartz and feldspar.

Megacrystic Biotite Gneiss (Cambrian/Late Proterozoic) at surface, covers < 0.1 % of this area

Poorly layered to massive; megacrysts of microcline and quartz; local mica schist, amphibolite, and biotite gneiss