Geologic units in McDowell county, North Carolina

Additional scientific data in this geographic area

Alligator Back Formation; Gneiss (Late Proterozoic) at surface, covers 23 % 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 22 % 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.

Biotite Granitic Gneiss (Middle Proterozoic) at surface, covers 10 % 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.

Henderson Gneiss (Cambrian) at surface, covers 10 % of this area

Monzonitic to granodioritic; inequigranular.

Migmatitic Granitic Gneiss (Ordovician/Cambrian) at surface, covers 8 % of this area

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

Amphibolite and Biotite Gneiss (Cambrian/Late Proterozoic) at surface, covers 5 % of this area

Interlayered; minor layers and lenses of hornblende gneiss, metagabbro, mica schist, and granitic rock.

Chilhowee Group; Upper Chilhowee (Cambrian) at surface, covers 5 % of this area

Vitreous quartzite, white to light gray; interbedded sandy metasiltstone and slate.

Mica Schist (Cambrian/Late Proterozoic) at surface, covers 4 % 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.

Ashe Metamorphic Suite and Tallulah Falls Formation; Metagraywacke (Late Proterozoic) at surface, covers 4 % of this area

Foliated to massive, locally conglomeratic; interlayered and gradational with mica schist, muscovite-biotite gneiss, and rare graphitic schist.

Rocks of Brevard Fault Zone (Uncertain, possibly Permian or Devonian) at surface, covers 3 % of this area

"Fish scale" schist and phyllonite, graphitic; interlayered with feldspathic metasandstone, marble lenses.

Metamorphosed Granitic Rock (Ordovician/Cambrian) at surface, covers 2 % of this area

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

Chilhowee Group; Lower Chilhowee (Cambrian) at surface, covers 2 % of this area

Feldspathic quartzite, white to yellowish gray. Minor silty slate, feldspathic metasiltstone, and metaconglomerate in lower part.

Shady Dolomite (Cambrian) at surface, covers 0.6 % of this area

Light gray, fine grained, massive, locally thin bedded or ribboned. Thin beds of phyllite.

Alligator Back Formation; Amphibolite (Late Proterozoic) at surface, covers 0.5 % of this area

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

Inequigranular Biotite Gneiss (Cambrian/Late Proterozoic) at surface, covers 0.5 % of this area

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

Granite Gneiss (Silurian/Ordovician) at surface, covers 0.1 % of this area

Poorly foliated; interlayered with biotite augen gneiss.

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.