Higgins Ferry Group; Garnet quartzite (garnetite) and garnitiferous altered mafic rock.

Hornblende gneiss member [of Collinsville Formation] - Dark, fine- to medium-grained, well-layered amphibolite and hornblende gneiss, composed of hornblende and plagioclase, commonly with biotite, garnet, or epidote, interlayered with light-gray felsic gneiss and pink quartz-spessartine rock (coticule). Grades into Bristol Gneiss.

Sweetheart Mountain Member [of Collinsville Formation] - Gray and silvery (not rusty), medium- to coarse-grained, poorly layered schist, composed of quartz, oligoclase, biotite, muscovite, and garnet, and in places kyanite or sillimanite. Amphibolite layers common; also layers of quartz-spessartine rock (coticule). In the Bristol quad., CT, Collinsville Formation is revised to include a basal unnamed hornblende gneiss member (was upper part of Stanley's (1964) Bristol Member), a middle unnamed metaquartzite member, and the upper Sweetheart Mountain Member. Bristol Member of Stanley (1964) is raised in rank to Bristol Gneiss in the report area. Collinsville unconformably underlies The Straits Schist. Inferred age is Middle Ordovician (Simpson, 1990).

Black and white, well-layered hornblende-biotite-plagioclase gneiss and amphibolite - Contains irregular pods of diopside or cummingtonite-talc rock or amphibole calc-silicate, epidote-layered quartz-plagioclase gneiss near Hinsdale.

Calc-silicate granofels and gneiss - Including calcitic or dolomitic chondrodite-diopside marble, coarse hornblende-plagioclase-diopside and diopside rock, locally containing beds of lustrous muscovite-kyanite sillimanite-garnet schist.

Silicified fault-breccia or strongly silicified metamorphic rocks.

Peavy Pond complex - Chiefly hornblende metagabbro, but includes metanorite, metatonalite, granodiorite, and granite (Bayley, 1959).

Pre-Belt gneiss, schist, and related rocks: comprises all the rocks older than the Belt series except the Stillwater complex. These include the Cherry Creek group, consisting of interlaminated gneiss, schist, marble, and quartzite; and the Pony series of Tansley and others, consisting of gneiss and schist of both sedimentary and igneous origin. Recent work has resulted in the distinction of small masses of granitic and injected rocks now regarded as resulting from intrusion in Cretaceous or Tertiary time. Other such masses may have escaped recognition.

Pre-Belt gneiss, schist, and related rocks: comprises all the rocks older than the Belt series except the Stillwater complex. These include the Cherry Creek group, consisting of interlaminated gneiss, schist, marble, and quartzite; and the Pony series of Tansley and others, consisting of gneiss and schist of both sedimentary and igneous origin. Recent work has resulted in the distinction of small masses of granitic and injected rocks now regarded as resulting from intrusion in Cretaceous or Tertiary time. Other such masses may have escaped recognition.

Amphibolite - metamorphosed mafic extrusive and intrusive rock; includes hornblende gneiss, thin layers of mica schist, and small nonlayered masses of metadiorite and metagabbro.

Amphibolite - metamorphosed mafic extrusive and intrusive rock; includes hornblende gneiss, thin layers of mica schist, calc-silicate rock, and, rarely, marble. Also includes small masses of metadiorite and metagabbro.

Amphibolite and Biotite Gneiss - interlayered; minor layers and lenses of hornblende gneiss, metagabbro, mica schist, and granitic rock.

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

Metamorphosed Gabbro and Diorite - foliated to massive.

Metamorphosed Gabbro and Diorite - foliated to massive.

Metamorphosed Gabbro and Diorite - foliated to massive.

Metamorphosed Gabbro and Diorite - foliated to massive.

Metamorphosed Gabbro and Diorite - foliated to massive.

Metamorphosed Granite (680-710 my) - massive to foliated, locally mylonitic. Equivalent to Brown Mountain Granite.

Metamorphosed Granitic Rock (455-540 my) - equigranular to megacrystic, foliated to massive. Includes Toluca Granite.

Metamorphosed Granitic Rock (520-650 my) - megacrystic, well foliated, locally contains hornblende; Fountain intrusive.

Metamorphosed Granitic Rock - megacrystic, well foliated; locally contains hornblende.

Metamorphosed Granitic Rock (520-650 my) - megacrystic, well foliated; locally contains hornblende. Chapel Hill, Chatham, Farrington, Meadow Flats, Mt. Moriah, Parks Crossroads plutons, and Roxboro and Vance County suites.

Metamorphosed Granitic Rock (680-710 my) - massive to foliated, locally mylonitic.

Metamorphosed Granitic Rock (520-650 my) - megacrystic, well foliated, locally contains hornblende; Vance County suite and Buckhorn granite.

Metamorphosed Mafic Rock - metagabbro, metadiorite, and mafic plutonic-volcanic complexes.

Metamorphosed Mafic Rock - metagabbro, metadiorite, and mafic plutonic-volcanic complexes.

Metamorphosed Quartz Diorite - foliated to massive.

Metamorphosed Quartz Diorite - foliated to massive.

Metamorphosed Quartz Diorite - foliated to massive.

Metamorphosed Quartz Diorite - foliated to massive.

Meta-ultramafic Rock - metamorphosed dunite and peridotite; serpentinite, soapstone, and other altered ultramafic rock. Only larger bodies shown.

Meta-ultramafic Rock - metamorphosed dunite and peridotite; serpentine, soapstone, and other altered ultramafic rock. Only larger bodies shown.

Meta-ultramafic Rock - metamorphosed dunite and peridotite; serpentine, soapstone, and other altered ultramafic rock. Only larger bodies shown.

Meta-ultramafic Rock - metamorphosed dunite and peridotite; serpentine, soapstone, and other altered ultramafic rock. Only larger bodies shown.

Meta-ultramafic Rock - metamorphosed dunite, local peridotite; serpentinite, soapstone, and other altered ultramafic rock. Only larger bodies shown.

Meta-ultramafic Rock - metamorphosed dunite, local peridotite, serpentinite, soapstone, and other ultramafic rock. Only larger bodies shown.

Lower Proterozoic metamorphic rocks, undivided

Latimer complex of Griffin (1979): metamorphosed mafic-ultramafic complex consisting mainly of mafic rocks including amphibolite, metagabbro, and greenstone metabasalt

Lockhart metadiorite: metadiorite and minor metagabbro, containing sparse hornblendite and pyroxenite

Mean Crossroads intrusive complex: metadiorite and minor metagabbro, containing sparse hornblendite and pyroxenite

Wildcat Branch complex: metadiorite and minor metagabbro, containing sparse hornblendite and pyroxenite

Buckingham Complex - Metamorphosed mafic and ultramafic rocks

Lahore Complex - Mafic and ultramafic rocks

Metagabbro

Mount Holly Complex, calcite and dolomite marbles - locally coarse grained; commonly contain phlogopite, actinolite, and diopside, and are interbedded with medium- to coarse-grained calc-silicate granulite; includes minor amounts of other types of Precambrian rock.

OLDEST GNEISS COMPLEX--Chiefly layered granitic gneiss, locally migmatitic. Local masses of quartzite, metagraywacke, iron-formation, and other metasedimentary rocks and amphibolite and felsic gneiss thought to be volcanic; metasedimentary rocks in Beartooth Mountains contain detrital zircon dated at more than 3,400 Ma. Inclusions show evidence of granulite-facies metamorphism prior to 2,800 Ma. Mueller and others (1982) suggest that large areas in Beartooth Mountains were invaded by Late Archean granite (age about 2,800 Ma). Bighorn Mountains--Dates of metamorphism 3,000+ Ma.