Geologic units in Madison county, North Carolina

Additional scientific data in this geographic area

Biotite Granitic Gneiss (Middle Proterozoic) at surface, covers 44 % 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.

Migmatitic Biotite-Hornblende Gneisses (Middle Proterozoic) at surface, covers 16 % 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 10 % of this area

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

Max Patch Granite (Late Proterozoic) at surface, covers 6 % of this area

Mottled pink and light green, coarse grained to porphyritic, massive; contains biotite.

Ocoee Supergroup; Walden Creek Group, undivided (Late Proterozoic) at surface, covers 6 % of this area

Slate to metasiltstone, locally limy beds and pods; interbedded with quartz-pebble metaconglomerate and metasandstone.

Ocoee Supergroup, Snowbird Group, undivided (Late Proterozoic) at surface, covers 4 % of this area

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

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.

Ocoee Supergroup, Snowbird Group; Roaring Fork Sandstone (Late Proterozoic) at surface, covers 3 % of this area

Greenish gray, fine to medium grained, locally cross-bedded, metamorphosed; interbedded metasiltstone and phyllite.

Ocoee Supergroup, Walden Creek Group; Sandsuck Formation (Late Proterozoic) at surface, covers 2 % of this area

Slate and metasiltstone, dark green to black. Metaconglomerate lentils in upper part; calcareous metasandstone, sandy metalimestone, and quartzite in lower part.

Chilhowee Group; Upper Chilhowee (Cambrian) at surface, covers 1 % 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; Longarm Quartzite (Late Proterozoic) at surface, covers 1 % of this area

Cross-bedded, feldspathic, locally conglomeratic; includes dark slate and metasiltstone.

Ocoee Supergroup, Snowbird Group; Pigeon Siltstone (Late Proterozoic) at surface, covers 1.0 % of this area

Thin bedded to laminated, commonly cross-bedded, metamorphosed; locally includes argillite and calcareous and arkeritic metasiltstone grading to silty metalimestone.

Ashe Metamorphic Suite and Tallulah Falls Formation; Muscovite-biotite gneiss (Late Proterozoic) at surface, covers 0.7 % of this area

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

Amphibolite (Middle Proterozoic) at surface, covers 0.7 % of this area

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

Rome Formation (Cambrian) at surface, covers 0.5 % of this area

Shale and siltstone, variegated red to brown; interbedded fine-grained sandstone and shaly dolomite.

Amphibolite (Middle Proterozoic) at surface, covers 0.5 % of this area

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

Shady Dolomite (Cambrian) at surface, covers 0.5 % of this area

Light gray, fine grained, massive, locally thin bedded or ribboned.

Ocoee Supergroup; Great Smokey Group, undivided (Late Proterozoic) at surface, covers 0.4 % of this area

Thick metasedimentary sequence of massive to graded beds of metagraywacke and metasiltstone with interbedded graphitic and sulfidic slate and schist.

Ocoee Supergroup, including Walden Creek Group, (including Sandsuck Formation, Wilhite Formation, Shields Formation, Licklog Formation), Cades Sandstone, and Rich Butt Sandstone (Precambrian) at surface, covers 0.1 % of this area

Ocoee Supergroup - Terrigenous clastic sedimentary rocks, for the most part poorly sorted and coarse. The groups are subdivided into formations only in the region of the Great Smoky Mountains. Thickness as much as 50,000 feet. Includes Walden Creek Group - The formations, other than the Sandsuck, have been mapped only in the region of the Great Smoky Mountains. Thickness about 8,000 feet; Sandsuck Formation - Olive-green and gray, argillaceous, micaceous shale with coarse feldspathic sandstone and quartz- pebble conglomerate. Thickness about 2,000 feet; Wilhite Formation - Gray to green siltstone and slate with interbeds of pebble conglomerate, sandstone, and quartzite. Thickness about 4,000 feet; Shields Formation - Massive conglomerate, sandstone, argillaceous slate; conglomerate (pebbles of various rock types) characteristic. Thickness about 1,500 feet; Licklog Formation - Feldspathic sandstone, greenish phyllite, and bluish-gray slate. Thickness about 1,500 feet; and the Cades Sandstone - Gray, well-bedded, fine- to medium-grained feldspathic metasandstone, with interbeds of dark slate and metasiltstone; precise stratigraphic position unknown. Thickness about 1,500 feet; and Rich Butt Sandstone - Gray, massive beds of feldspathic, fine- to medium-grained sandstone, with interbeds of dark slate and arkosic conglomerate; exact stratigraphic position unknown. Thickness about 1,500 feet.

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.

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.

Ocoee Supergroup, Snowbird Group; Wading Branch Formation (Late Proterozoic) at surface, covers < 0.1 % of this area

Sandy slate to coarse-grained pebbly metagraywacke with local graded bedding. Basal quartz-sericite schist or phyllite.

Coweeta Group; Biotite Gneiss (Middle/Late Proterozoic) at surface, covers < 0.1 % of this area

Migmatitic; interlayered and gradational with biotite-garnet gneiss and amphibolite; locally abundant quartz and alumino-silicates. Stratigraphic position uncertain.

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.

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.

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

Dark greenish-gray, silty and sandy, micaceous shale; numerous layers of medium-grained, feldspathic, thinly bedded sandstone. Thickness 500 to 2,000 feet.

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.

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

White, vitreous quartzite, massive, with interbeds of dark-green silty and sandy shale, minor siltstone, and very fine-grained sandstone. Thickness 1,000 to 1,500 feet.

Sandsuck Formation (Precambrian) at surface, covers < 0.1 % of this area

Olive-green and gray, argillaceous, micaceous shale with coarse feldspathic sandstone and quartz- pebble conglomerate. Thickness about 2,000 feet.