Description of Map Units: Bedrock Geology and Mineral Resources of the Knoxville 1°x 2° Quadrangle, Tennessee, North Carolina and South Carolina (Robinson, et. al., 1991).

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Valley and Ridge and West Flank Blue Ridge

Sedimentary and

Metamorphic rocks

Bedrock Unit

Description

MDu

Mississippian and Devonian rocks, undivided; includes Greasy Cove Formation (gray argillacious limestone, calcareous shale, siltstone, and fine grained sandstone), Grainger Formation (gray to green shale with siltstone and fine-grained glauconitic sandstone, and Chattanooga Shale (dark gray to black; carbonaceous; locally sulfidic)

Oc

Chickamauga Group, undivided (Upper and Middle Ordovician); limestone, sandy limestone and calcareous shale; dark gray to red; locally coarse bioclastic

C-k

Knox Group, undivided (Lower Ordovician and Upper Cambrian)- well bedded limestone and dolomite; commonly dark-colored; locally cherty

C-u

Cambrian rocks, undivided; Conasauga Group (thin-bedded dolomite and limestone; interbedded shale and siltstone), Rome Formation (shale and siltstone, variegated red to brown; interbedded fine-grained sandstone and shaly dolomite), Shady Dolomite (light-gray, fine-grained, massive, locally thin-bedded or ribboned; locally shaly)

C-Zc

Chilhowee Group, undivided (Lower Cambrian and Late Proterozoic); Murphy Belt; vitreous quartz arenite and feldspathic arenite with interbedded sandy siltstone and shale; conglomerate in lower part

Central and West Flank Blue Ridge

Metamorphic rocks

Murphy Belt

Bedrock Unit

Description

C-b

Brasstown Schist (Lower Cambrian?); cross-biotite schist, includes micaceous quartzite in lower part

C-nt

Nantahala Formation and Tusquitee Quartzite, undivided (Cambrian? and Lower Cambrian); Nantahala Formation (slate and metasandstone, dark gray, laminated to thin-bedded, sulfidic), Tusquitee Quartzite (white to light yellowish gray, numerous thin slate layers)

C-amn

Andrews Formation, Murphy Marble, and Nottely Quartzite, undivided (Cambrian?); Andrews Formation (calcareous cross-biotite schist), Murphy Marble (calcareous to dolomitic marble), Nottely Quartzite (metaorthoquartzite with slate)

Zmb

Mineral Bluff Formation of Hurst (1955) (Late Proterozoic); quartz-chlorite-sericite schist and phyllite within quartzite layers and minor interbedded graphitic schist, garnet-mica schist, staurolite schist, cross-biotite schist, and dark slate

                                         Ocoee Supergroup

Bedrock Unit

Description

Zw

Walden Creek Group (Late Proterozoic), Ocoee Supergroup; slate to metasandstone, local calcareous beds and lenses; interbedded with metasandstone and quartz-pebble metaconglomerate

Zg

Great Smoky Group, undivided (Late Proterozoic);  thick metasedimentary sequence of massive to graded beds of metagraywacke and metasiltstone with interbedded metasandstone and metaconglomerate, and in some places graphitic and sulfidic slate and schist

Zgd

Dean Formation (Late Proterozoic); sericite schist with cross-biotite, staurolite, and garnet porphyroblasts; interbedded metagraywacke and quartz-pebble metaconglomerate)

Zgsg

Sandstone, graywacke, and siltstone (Late Proterozoic); variably metamorphosed; beds and lenses of mica schist and calcsilicate rock locally abundant; garnet, staurolite, and cross-biotite porphyroblasts common in fine grained layers

Zgw

Wehutty Formation (Late Proterozoic); slate to schist, dark gray, graphitic and sulfidic; includes mica schist, metagraywacke, and metaconglomerate

Zgc

Copperhill Formation (Late Proterozoic); metagraywacke, massive, graded bedding common; includes dark-gray slate, mica schist, and nodular calcsilicate rock)

Zgcs

Slate of Copperhill Formation (Late Proterozoic); slate to phyllite, dark gray, graphitic, sulfidic; includes metagraywacke with local grade bedding)

Zga

Anakeesta Formation (Late Proterozoic); slate to schist, dark gray, graphitic and sulfidic; includes interbedded argillaceous, feldspathic metagraywacke)

Zr

Rich Butt Sandstone (Late Proterozoic); feldspathic; interbedded with dark argillaceous layers and laminae; includes Cades Sandstone in Cases Cove window

ZYs

Snowbird Group (Late and (or) Middle Proterozoic);  feldspathic metasiltstone, metasandstone, and phyllite; basal schist contains lenses of quartz-pebble conglomerate.

Unconformity

Bedrock Unit

Description

Ybg

Biotite gneiss (Middle Proterozic); uncomformity; pinkish gray to light gray, massive to well-foliated, granitic to quartz monzonite; includes variably mylonitized orthogneiss and paragneiss, interlayered amphibolite, calcsilicate rock, and marble

Intrusive Rocks

Bedrock Unit

Description

C-Zmd

Metadiorite (Cambrian and Late Proterozoic); equigranular, massive to well-foliated, dioritic to basaltic dikes and sills; variably metamorphosed

Zm

Max Patch Granite; mottled pink and light green, coarse-grained to porphyritic, massive, contains biotite

East Flank Blue Ridge

Metamorphic Rocks

     (stratigraphic order uncertain)

Tallulah Falls Sheet (Ashe Metamorphic Suite, Late Proterozoic)

Bedrock Unit

Description

Zal

Laminated biotite gneiss (Late Proterozoic); finely laminated to thin-layered; locally contains massive gneiss and micaceous granule conglomerate; includes schist, phyllite, and amphibolite

Zam

Metagraywacke (Late Proterozoic); foliated to massive, locally conglomeratic; interlayered and gradational with mica schist, muscovite-biotite gneiss, and rare graphitic schist

Zak

Kyanite schist and gneiss (Late Proterozoic); massive and interlayered with quartz schist and biotite gneiss; garnet, staurolite, and (or) sillimanite commonly occur; aluminous

Zamb

Muscovite-biotite gneiss (Late Proterozoic); locally sulfidic; interlayered and gradational with mica schist, minor amphibolite, and hornblende gneiss

Zab

Biotite gneiss (Late Proterozoic); interlayered with biotite-garnet gneiss, biotite-muscovite schist, garnet-mica schist, and amphibolite

Zaa

Amphibolite (Late Proterozoic); equigranular, massive to well-foliated, interlayered, rarely discordant, metamorphosed intrusive and extrusive mafic rock; may include metasedimentary rock

Unconformity

Bedrock Unit

Description

Ytg

Toxaway Gneiss (Middle Proterozoic, correlated with biotite gneiss unit Ybg); unconformity; poorly foliated to well-foliated; equigranular to inequigranular, granitic

Helen Sheet

Bedrock Unit

Description

PzZh

Helen Group (Lower Paleozoic and Late Proterozoic);  interlayered metasandstone, metasiltstone, aluminous schist, and amphibolite; locally sulfidic; includes areas of granitic pegmatite

Richard Russell Sheet and amphibolitic basement complex

Bedrock Unit

Description

Zc

Coweeta Group of Hatcher (1979) (Late Proterozoic?);  quartz dioritic gneiss and feldspar-quartz-biotite gneiss; quartz dioritic gneiss predominant

Richard Russell Formation and amphibolitic basement complex

Bedrock Unit

Description

Yga

Biotite gneiss and amphibolite (Middle Proterozoic); layered biotite granite gneiss and biotite-hornblende gneiss; interlayered and gradational with biotite-garnet gneiss, calcsilicate rock, marble, and amphibolite; locally contains granite gneiss and relict granulite facies rock; locally migmatitic. Larger bodies of amphibolite shown separately as unit PzYa. U/Pb zircon age of 1035 Ma (Stern and Nelson, unpublished) and Rb/Sr whole-rock age of 1214 Ma (Fullagar and Odum, 1973; Fullagar and others, 1979) from granite gneiss bodies

c

Corundum-bearing rock; layered biotite gneiss containing corundum; may be associated with bodies of ultramafic rock (smaller bodies noted in rock deposit coverage)

PzYa

Amphibolite (Early Paleozoic to Middle Proterozoic); equigranular, massive to well-foliated, interlayered, rarely discordant, metamorphosed intrusive and extrusive mafic rock; may include ultramafic and metasedimentary rock

Intrusive and other igneous rocks

Bedrock Unit

Description

Dqd

Quartz diorite to granodiorite (Devonian); contains biotite, muscovite, and xenocrysts; includes Whiteside Mtn., Rabun (in part), Spruce Pine, and other smaller plutons. U/Pb zircon age of 373+20 Ma (Stern and Nelson, unpublished) and Rb/Sr whole-rock age of 390-400 Ma (Kish and others, 1976)

SOg

Granitic gneiss (Silurian and Ordovician); weakly to well-foliated, granitic to quartz monzonitic; includes Rabun pluton, in part. U/Pb zircon age of 431 Ma (Stern and Nelson, unpublished) and Rb/Sr whole-rock age of 420-460 Ma (Kish and others, 1976)

u

Metaultramafic rock, undifferentiated (Early Paleozoic and Late Proterozoic); metamorphosed dunite, peridotite, serpentinite, soapstone, and other altered ultramafic rock (smaller bodies noted in rock deposit coverage)

ud

Dunite and peridotite (Early Paleozoic and Late Proterozoic); smaller bodies noted in rock deposit coverage

up

Pyroxenite (Early Paleozoic and Late Proterozoic); smaller bodies noted in rock deposit coverage

us

Talc schist, soapstone, and serpentinite (Early Paleozoic and Late Proterozoic); smaller bodies noted in rock deposit coverage

Inner Piedmont

Metamorphic Rocks

Bedrock Unit

Description

sb

Silicified breccia; silicified crushed rock and breccia

bz

Rocks of Brevard fault zone (age uncertain, possibly Permian or Devonian); schist, mylonitic gneiss, and phyllonite; graphitic; interlayered with feldspathic gneiss, marble lenses

C-Zbg

Biotite gneiss and schist (Cambrian and Late Proterozoic); inequigranular, locally abundant potassic feldspar and garnet; interlayered and gradational with calcsilicate rock, sillimanite-mica schist, mica schist, and amphibolite; contains small masses of granitic rock

C-Zms

Mica schist (Cambrian and Late Proterozoic); massive and interlayered with lenses and layers of quartz schist, micaceous quartzite, calcsilicate rock, biotite gneiss, amphibolite, and phyllite; garnet, staurolite, kyanite, or sillimanite occur locally

C-Zab

Amphibolite and biotite gneiss (Cambrian and Late Proterozoic); interlayered; minor layers and lenses of hornblende gneiss, metagabbro, mica schist, and granite rock

C-Zpg

Porphyroblastic biotite gneiss (Cambrian and Late Proterozoic); massive to foliated, contains plagioclase megacrysts and, rarely, megacrysts of quartz and feldspar; granodioritic, locally migmatitic

C-Zgs

Garnet-mica schist; interlayered with amphibolite

Intrusive rocks

Bedrock Unit

Description

Jd

Diabase (Jurassic); dikes, gray to black

SOc

Caesars Head Granite (Early Silurian and Ordovician); equigranular to porphyritic; massive to well-foliated granite gneiss; contains biotite and muscovite

SOg

Granite gneiss (Silurian and Ordovician); poorly foliated; interlayered with biotite augen gneiss

Omg

Migmatitic granite gneiss (Ordovician); foliated to massive, granitic to quartzdioritic; biotite gneiss and amphibolite common

C-h

Henderson Gneiss (Cambrian); monzonitic to granodioritic, inequigranular