Geologic units in Mitchell county, North Carolina

Additional scientific data in this geographic area

Migmatitic Biotite-Hornblende Gneisses (Middle Proterozoic) at surface, covers 21 % of this area

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

Granodioritic Gneiss (Middle Proterozoic) at surface, covers 19 % of this area

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

Ashe Metamorphic Suite and Tallulah Falls Formation; Muscovite-biotite gneiss (Late Proterozoic) at surface, covers 15 % of this area

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

Alligator Back Formation; Gneiss (Late Proterozoic) at surface, covers 12 % of this area

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

Ashe Metamorphic Suite and Tallulah Falls Formation; Amphibolite (Late Proterozoic) at surface, covers 11 % of this area

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

Biotite Granitic Gneiss (Middle Proterozoic) at surface, covers 7 % 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.

Alligator Back Formation; Amphibolite (Late Proterozoic) at surface, covers 7 % of this area

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

Quartz Diorite to Granodiorite (Devonian) at surface, covers 4 % of this area

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

Chilhowee Group; Lower Chilhowee (Cambrian) at surface, covers 3 % 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.

Chilhowee Group; Upper Chilhowee (Cambrian) at surface, covers 0.4 % of this area

Vitreous quartz arenite, white to light gray; interbedded sandy siltstone and shale. Erwin and Hampton formations of Hot Springs window.

Ocoee Supergroup, Snowbird Group, undivided (Late Proterozoic) at surface, covers 0.3 % of this area

Feldspathic metasiltstone, metasandstone, and phyllite. Basal schist contains lenses of quartz-pebble conglomerate.

Unicoi Formation (Cambrian) at surface, covers 0.2 % 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.

Cranberry Granite (Precambrian) at surface, covers 0.2 % of this area

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

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.

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.

Snowbird Group, including Pigeon Siltstone, Roaring Fork Sandstone, Metcalf Phyllite, Longarm Quartzite, and Wading Branch Formation (Precambrian) at surface, covers < 0.1 % of this area

Snowbird Group - The formations at right are applicable chiefly in the area of the Great Smoky Mountains. Thickness 13,000 to about 20,000 feet. Includes Pigeon Siltstone - Laminated, greenish quartzose and feldspathic siltstone; minor fine-grained gray sandstone. Thickness as much as 10,000 feet; Roaring Fork Sandstone - Interbedded massive feldspathic sandstone, greenish siltstone, and greenish phyllite. Maximum thickness 7,000 feet; Metcalf Phyllite - Lustrous, pale-green and silvery sericitic and chloritic phyllite; siltstone interbeds abundant. Thickness uncertain; at least 5,000 feet; Longarm Quartzite - Feldspathic quartzite and arkose, conspicuously light-colored, current bedded and crossbedded. Thickness about 5,000 feet; Wading Branch Formation - Medium- to dark-gray sandy slate to coarse, pebbly feldspathic sandstone and graywacke; basal part is quartz-sericite phyllite; graded bedding common. Thickness about 1,500 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.