Geologic units in Avery county, North Carolina

Additional scientific data in this geographic area

Biotite Granitic Gneiss (Middle Proterozoic) at surface, covers 26 % 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.

Grandfather Mountain Formation; Meta-arkose (Late Proterozoic) at surface, covers 12 % of this area

Sericitic, conglomeratic, locally cross-bedded; interlayered metasiltstone and slate.

Migmatitic Biotite-Hornblende Gneisses (Middle Proterozoic) at surface, covers 11 % of this area

Unconformity; layered biotite-granite gneiss, biotite-hornblende gneiss, amphibolite, calc-silicate rock; locally contains relict granulite facies rock.

Grandfather Mountain Formation; Metagraywacke (Late Proterozoic) at surface, covers 9 % of this area

Cross-bedding and graded bedding common, locally conglomeratic; interlayered with metasiltstone and phyllite.

Ashe Metamorphic Suite and Tallulah Falls Formation; Amphibolite (Late Proterozoic) at surface, covers 9 % of this area

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

Ashe Metamorphic Suite and Tallulah Falls Formation; Muscovite-biotite gneiss (Late Proterozoic) at surface, covers 7 % of this area

Locally sulfidic; interlayered and gradational with mica schist, minor amphibolite, and hornblende gneiss.

Metamorphosed Granitic Rock (Late Proterozoic) at surface, covers 6 % of this area

Massive to foliated, locally mylonitic. Beech, Crossnore, Brown Mountain, Lansing, and other granitic rocks.

Alligator Back Formation; Gneiss (Late Proterozoic) at surface, covers 5 % of this area

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

Grandfather Mountain Formation; Greenstone (Late Proterozoic) at surface, covers 3 % of this area

Schistose to massive, amygdaloidal; interlayered with metasedimentary rocks. Includes Montezuma Member (metabasalt) in upper part.

Biotite Granitic Gneiss (Middle Proterozoic) at surface, covers 3 % of this area

Unconformity; pinkish gray to light gray, massive to well-foliated, granitic to quartz monzonitic; includes variably mylonitized orthogneiss and paragneiss, interlayered amphibolite, calc-silicate rock, and marble. Includes granites of the Bryson City area, Straight Fork window, and Elk Park Plutonic Suite.

Grandfather Mountain Formation; Metasiltstone (Late Proterozoic) at surface, covers 3 % of this area

Locally contains thin bedded iron-bearing dolomitic marble; interlayered with phyllite, metagraywacke, and meta-arkose.

Linville Metadiabase (Late Proterozoic) at surface, covers 3 % of this area

Metadiabase, greenstone, and amphibolite dikes and sills; massive to schistose.

Granodioritic Gneiss (Middle Proterozoic) at surface, covers 1.0 % of this area

Unconformity; greenish gray to pinkish gray, porphyroclastic to mylonitic; epidote, sericite, and chlorite common.

Quartz Diorite to Granodiorite (Devonian) at surface, covers 1.0 % of this area

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

Chilhowee Group; Upper Chilhowee (Cambrian) at surface, covers 0.5 % of this area

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

Chilhowee Group; Lower Chilhowee (Cambrian) at surface, covers 0.5 % of this area

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

Alligator Back Formation; Amphibolite (Late Proterozoic) at surface, covers 0.3 % of this area

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

Metamorphosed Granite (Late Proterozoic) at surface, covers 0.1 % of this area

Massive to foliated, locally mylonitic. Equivalent to Brown Mountain Granite.

Cranberry Granite (Precambrian) at surface, covers < 0.1 % of this area

Complex of intertonguing rock types including migmatite, granitic gneisses, monzonite, quartz diorite, greenstone, mica and hornblende schists, abundant granitic pegmatite.

Beech Granite (Precambrian) at surface, covers < 0.1 % of this area

Granite, porphyritic, light-gray to reddish; coarse potash feldspar crystals and clustered interstitial mafics (chloritized biotite and hornblende) give spotted appearance; includes Max Patch Granite.

Chilhowee Group; Lower Chilhowee (Cambrian) at surface, covers < 0.1 % of this area

Feldspathic arenite, white to yellowish gray. Minor silty shale, feldspathic siltstone, and conglomerate in lower part. Includes Unicoi Formation of Hot Springs window.

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.

Unicoi Formation (Cambrian) at surface, covers < 0.1 % of this area

Sequence of gray feldspathic sandstone, arkose, conglomerate, graywacke, siltstone and shale; greenish amygdaloidal basalt flows near middle and base. Thickness 2,000 to 5,000 feet.

Bakersville Gabbro (Precambrian) at surface, covers < 0.1 % of this area

Metagabbro, dark, porphyritic; contains diorite, basalt, anorthosite, and diabase; occurs as thin to massive dikes and lenticular masses.

Roan Gneiss (Precambrian) at surface, covers < 0.1 % of this area

Layered hornblende and garnet gneiss and granitic migmatite with zones of mica schist and amphibolite, foliation commonly contorted; contains numerous granitic and gabbroic dikes.