SD016
Areas not mapped
Areas not to be filled that lie within coverage, typically not mapped.
Unknown
Sumdum
TR008
Taku River
JU012
Juneau
Qs
BC006
Surficial sedimentary deposits
Unnamed lacustrine, fluvial, colluvial, glacial, beach, and marine deposits.
Quaternary
Bradfield Canal
Unconsolidated
CR012
Craig
KC013
Ketchikan
MF011
Mount Fairweather
PA006
Port Alexander
PE006
Petersburg
PR003
Prince Rupert
SI009
Sitka
SK015
Skagway
QTv
Volcanic rocks
Basalt, andesite, dacite and rhyolitic rocks.
Quaternary and Tertiary
Igneous
Ts
Sedimentary rocks
Nonmarine sandstone, shale, conglomerate, and marine calcareous sandstone and siltstone
Tertiary
Sedimentary
QTs
Pleistocene to Miocene marine mudstone, siltstone, sandstone, and conglomerate.
Tsv
Sedimentary and volcanic rocks, undivided
Carbonaceous shale, sandstone, conglomerate, and subordinate volcanic rocks.
Tv
Oligocene and Eocene basalt and andesite.
Tgr
Granite
Biotite +/- hornblende +/- pyroxene granite, alkali granite, quartz monzonite, and subordinate syenite, granodiorite, and diorite.
Tertiary (Miocene and Oligocene)
Stocks on mainland southeast of Revillagigedo Island yield potassium-argon apparent ages of early Miocene and Oligocene (Berg and others, 1978, 1988).
Tgb
Gabbro
Layered and locally zoned bodies of two-pyroxene +/- olivine +/- biotite +/- hornblende +/- quartz gabbro and subordinate troctolite, peridotite, leucogabbro, diorite, and tonalite.
Stocks on Revilagigedo Island and adjacent area of mainland yield potassium-argon apparent ages of early Miocene and late Oligocene (Smith and Diggles, 1981), and large body (La Perouse gabbro) northwest of Cross Sound yields a 40Ar/39Ar apparent age of
Tgd
Granodiorite
Biotite +/- hornblende +/- muscovite +/- garnet granodiorite, granite, quartz monzonite, tonalite, and quartz diorite.  (Where shown having a stippled overprint on map, consists of undifferentiated intrusive and stratified rocks where the map unit symbol
Tertiary (Oligocene and Eocene)
Where dated, these intrusive bodies yield Eocene potassium-argon apparent ages (Loney and others, 1975; Decker and Plafker, 1982; Johnson and Karl, 1985; Brew and others, 1978).
Biotite +/- hornblende +/- muscovite +/- garnet granodiorite, granite, quartz monzonite, tonalite, and quartz diorite.
Q
Tgd?
Tgd ?
Tg
Biotite-dominant, hornblende- and sphene-bearing granodiorite and subordinate quartz monzonite, quartz diorite, and leucogranite.
Tertiary (Eocene)
Concordant potassium-argon apparent ages on hornblende and biotite (Forbes and Engels, 1970; Smith and others, 1979) and uranium-lead (zircon) apparent ages (Gehrels and others, 1984) indicate emplacement during Eocene time.
Biotite-dominant, hornblende- and sphene-bearing granodiorite and subordinate quartz monzonite, quartz diorite, and leucogranite.  (Where shown having a stippled overprint on map, consists of undifferentiated intrusive and stratified rocks where the map
Tg?
Tgt
Granodiorite and tonalite
Biotite-dominant, hornblende-bearing granodiorite and tonalite containing local foliation and layering.
Tertiary (Paleocene)
Uranium-lead (zircon) data indicate emplacement during Paleocene time (Gehrels and others, 1984).
Tgt?
TKg
Diverse assemblage of generally foliated and layered granodiorite, quartz monzonite, tonalite, and their metamorphic equivalents. May include a significant component of pre-Tertiary metasedimentary and metavolcanic rocks (pTmsv) in some areas.  (Where sh
Tertiary (Paleocene) and Cretaceous
Diverse assemblage of generally foliated and layered granodiorite, quartz monzonite, tonalite, and their metamorphic equivalents. Includes a significant component of pre-Tertiary metasedimentary and metavolcanic rocks (pTmsv).  (Where shown having a stip
Diverse assemblage of generally foliated and layered granodiorite, quartz monzonite, tonalite, and their metamorphic equivalents. May include a significant component of pre-Tertiary metasedimentary and metavolcanic rocks (pTmsv) in some areas
TKg?
TKt
Tonalite
Hornblende-dominant, biotite-bearing tonalite and subordinate quartz diorite found as steeply dipping, foliated, and locally lineated sills.
Field and uranium-lead (zircon) data indicate emplacement in Paleocene and Late Cretaceous time, during waning stages of deformation and metamorphism in Coast Mountains (Gehrels and others, 1984; Brew and Ford, 1981).
TKt?
KJv
Andesite to basaltic flows, flow breccia, agglomerate, and tuff (generally containing conspicuous clinopyroxene phenocrysts), subordinate graywacke and mudstone, and regionally metamorphosed and deformed equivalents of these strata. Greenschist facies me
Cretaceous and Jurassic
KJv?
Kgt
Small plutons to batholiths of granodiorite, tonalite, and subordinate quartz monzonite to quartz diorite and diorite. Most bodies contain biotite and hornblende, many have magmatic epidote and garnet and are plagioclase porphyritic, and some contain pyr
Cretaceous
Potassium-argon and 40Ar/39Ar, and uranium-lead apparent ages of these bodies are generally Late Cretaceous (Smith and Diggles, 1981; Brew and others, 1984; Sutter and Crawford, 1985; Rubin and Saleeby, 1987).
Kgt?
Kg
A heterogeneous suite of plutons consisting primarily of biotite, hornblende, magnetite +/- pyroxene +/- garnet granodiorite and subordinate quartz monzonite, tonalite, trondhjemite, and quartz diorite.
Potassium-argon apparent ages record emplacement primarily during Early Cretaceous time, although similar intrusive bodies northwest of Glacier Bay in Canada also yield Jurassic potassium-argon apparent ages (Chris Dodds, oral commun., 1984).
DE008
Dixon Entrance
A heterogeneous suite of plutons consisting primarily of biotite, hornblende, magnetite +/- pyroxene +/- garnet granodiorite and subordinate quartz monzonite, tonalite, trondhjemite, and quartz diorite.  (Where shown having a stippled overprint on map, c
Kg?
Kdb
Diorite and gabbro
Hornblende diorite and gabbro that grades laterally into granodiorite and quartz diorite (unit Kgt).
Potassium-argon ages are Late Cretaceous (Redman and others, 1984).
Kum
Ultramafic rocks
Ultramafic intrusive bodies of magnetite-bearing hornblende clinopyroxenite and subordinate dunite, peridotite, and hornblendite (Taylor, 1967). Several complexes are concentrically zoned from a core of dunite to rocks containing progressively less olivi
Potassium-argon apparent ages of the ultramafic rocks indicate emplacement during Early Cretaceous time (Lanphere and Eberlein, 1966).
Kum?
Kd
Diorite
Primarily hornblende +/- biotite +/- clinopyroxene diorite and subordinate quartz diorite and gabbro.
Primarily hornblende +/- biotite +/- clinopyroxene diorite and subordinate quartz diorite and gabbro.  (Where shown having a stippled overprint on map, consists of undifferentiated intrusive and stratified rocks where the map unit symbol and color in sti
Kd?
Kgb
Primarily clinopyroxene (generally augite) +/- hornblende +/- biotite +/- olivine gabbro, leucogabbro, and subordinate norite, syenite, and pyroxenite.
Primarily clinopyroxene (generally augite) +/- hornblende +/- biotite +/- olivine gabbro, leucogabbro, and subordinate norite, syenite, and pyroxenite.  (Where shown having a stippled overprint on map, consists of undifferentiated intrusive and stratifie
KJs
Marine graywacke and mudstone, subordinate conglomerate and andesitic to basaltic volcanic rocks, minor limestone, and regionally metamorphosed and deformed equivalents of these strata. Metamorphic grade generally increase from subgreenschist facies or n
Fossils range in age from Cenomanian or Albian to Late and possibly Middle Jurassic (Breg and others, 1972; Brew and others, 1984).
KJs?
KJsv
Moderately deformed and metamorphosed graywacke, mudstone, sandstone, and andesitic to basaltic rocks.
Metamorphic
Ksm
Includes sedimentary and metasedimentary rocks that are similar in structural and metamorphic characteristics to rocks in the Cretaceous sedimentary and volcanic melange unit (Ksvm). Common lithic types include dark-gray phyllite, light-gray quartzite, a
Fossils were not recovered from rocks in this unit.
Ksv
Interbedded sedimentary and volcanic rocks, and their metamorphosed equivalents.
Ksv?
Ks
Sandstone and mudstone turbidites and subordinate conglomerate and regionally metamorphosed carbonaceous siltstone, volcanogenic graywacke, mudstone, and minor conglomerate.
Early Cretaceous fossils were found in the Sitka Graywacke on Kruzof Island (Reed and Coats, 1941)
Kv
Schist, gneiss, and amphibolite.
KJgb
Two-pyroxene gabbro and subordinate hornblende +/- biotite gabbro and diorite.
KJgd?
Two-pyroxene gabbro and subordinate hornblende +/- biotite gabbro and diorite.  (Polygon erroneously labeled KJgd on map, should have been KJgb).
Ksvm
Marine sedimentary and volcanic rocks, and their metamorphic equivalents, that are bounded by fault or shear zones; and marine sedimentary and volcanic rocks, and their metamorphic equivalents, enclosed in a matrix of moderately metamorphosed and penetra
Fossils from blocks are Early Cretaceous, Late Jurassic(?) or Triassic(?) in age (Loney and others, 1975; Johnson and Karl, 1985).  Minimum age of unit is constrained by (1) mid-Cretaceous potassium-argon apparent ages on metamorphic minerals in the mela
Minimum age of unit is constrained by (1) mid-Cretaceous potassium-argon apparent ages on metamorphic minerals in the melange on Chichagof Island (Decker and others, 1980)
Tectonite
Ksvm?
Marine sedimentary and volcanic rocks, and their metamorphic equivalents, that are bounded by fault or shear zones; and Marine sedimentary and volcanic rocks, and their metamorphic equivalents, enclosed in a matrix of moderately metamorphosed and penetra
Fossils from blocks are Early Cretaceous, Late Jurassic (?) or Triassic (?) in age (Loney and others, 1975; Johnson and Karl, 1985).  Minimum age of unit is constrained by (1) mid-Cretaceous potassium-argon apparent ages on metamorphic minerals in the me
Minimum age of unit is constrained by (1) mid-Cretaceous potassium-argon apparent ages on metamorphic minerals in the melange on Chichagof Island (Decker and others, 1980) [...]
Kvm
Includes mafic volcanic and metavolcanic rocks that resemble rocks in the Cretaceous sedimentary and volcanic rocks melange unit (Ksvm) in structural and metamorphic characteristics. Common rock types include greenstone, greenschist, and minor phyllite,
Includes mafic volcanic and metavolcanic rocks that resemble rocks in the Cretaceous sedimentary and volcanic rocks melange unit (Ksvm) in structural and metamorphic characteristics. Common lithic types include greenstone, greenschist, and minor phyllite
KDsd
Deformed, disrupted, and metamorphosed graywacke, siltstone, mudstone, and subordinate chert, limestone, and volcanic and intrusive rocks that belong to a belt of regionally disrupted rocks in the Kupreanof-Etolin Islands area. Common metamorphic rock ty
Cretaceous to Devonian
KDvd
Deformed, disrupted, and metamorphosed mafic to intermediate and minor felsic volcanic rocks that belong to a belt of regionally disrupted rocks in the Kupreanof-Zarembo Islands area. Rocks generally metamorphosed to greenschist and greenstone.
KJd
Metamorphosed and moderately deformed diorite and subordinate quartz diorite and gabbro.
A small quartz diorite body near northern Annette Island yielded a Cretaceous potassium-argon apparent age; the other bodies are undated.
KJd?
Jt
Biotite and hornblende tonalite and quartz diorite.
Jurassic
Biotite and hornblende tonalite and quartz diorite on Chichagof Island that yielded a Middle Jurassic potassium-argon (hornblende) apparent age (Loney and others, 1975).
Jgr
Peralkaline aegerine and arfvedsonite granite.
Peralkaline aegerine and arfvedsonite granite (Bokan Mountain Granite) on southern Prince of Wales Island (MacKevett, 1963) yielded Jurassic potassium-argon (Lanphere and others, 1964), uranium-lead (zircon) (Saint-Andre and others, 1983), and rubidium-s
Jgr?
Trg
Hornblende and biotite granodiorite and minor quartz diorite.
Triassic
Unit yielded a latest Triassic potassium-argon (hornblende) apparent age (Smith and Diggles, 1981).
JTrd
Hornblende and biotite diorite (Jualin Diorite).
Jurassic and (or) Triassic
Trsc
Clastic sedimentary and carbonate rocks, undivided
Unnamed, moderately deformed and metamorphosed graphitic limestone.
Trgb
Two-pyroxene gabbro.
Two-pyroxene gabbro on Duke Island (Irvine, 1974) and Percy Islands (Berg and others, 1978, 1988) that yields a Late Triassic uranium-lead (zircon) apparent age (Gehrels and others, 1987).
Trgb?
Trb
Basaltic rocks
Basaltic flows and flow breccia (Goon Dip Greenstone) that were deposited, at least in part, in subaerial environments, and unnamed basalt.
Basalt near Haines yields Carnian fossils and is also interpreted by Davis and Plafker (1985) to be correlative with the Nikolai Greenstone.
Trs
Upper Triassic conglomerate, limestone, and calcareous siltstone and sandstone, silty limestone, and conglomerate and sedimentary breccia.
Trs?
Trsv
Black shale, shaly limestone, siltstone, sandstone, conglomerate, and limestone; felsic, intermediate, and mafic flows; and minor black chert. Rocks vary from relatively unmetamorphosed to as high as greenschist facies. Common rock types in higher grade
Trc
Carbonate rocks
Massive to thick-bedded limestone and minor dolomite in most areas, but in Keku Strait unit includes thin-bedded, dark-gray limestone, and on Chichagof Isalnd unit consists of massive white to gray marble (Whitestripe Marble).
Diagnostic fossils from limestone and dolomite are Late Triassic in age.
Trv
Volcanic rocks (rhyolitic to basaltic)
Basaltic pillow flows, pillow breccia and breccia; rhyolitic tuff with calcareous interbeds, flow breccia, and banded ash-flow tuff, and subordinate andesitic breccia and aquagene tuff. Rocks in most areas are moderately recrystallized and deformed.
Fossils from interbedded rocks or from conformable adjacent strata indicate deposition during Norian and Carnian time.
TrPc
Unfossiliferous marble.
Triassic and (or) Permian
TrPc?
KPs
Carbonaceous shale, mudstone, and graywacke; subordinate limestone, chert, conglomerate, and mafic volcanic rocks; minor felsic volcanic rocks; and the metamorphosed and deformed equivalents of these rocks.
Cretaceous to Permian
Triassic fossils were recovered from carbonaceous slate and limestone assigned to this map unit near Juneau (Ford and Brew, 1977; H.C. Berg, unpub. data, 1981), and similar strata (locally mapped as Triassic clastic sedimentary and carbonate rocks (Trsc)
KPs?
KPsv
Shale, mudstone, graywacke, andesitic or basaltic rocks, subordinate chert and carbonate rocks, and the regionally metamorphosed equivalents of these strata.
Shale, mudstone, graywacke, andesitic or basaltic rocks, subordinate chert and carbonate rocks, and the regionally metamorphosed equivalents of these strata.  (Where shown having a stippled overprint on map, consists of undifferentiated intrusive and str
KPv
Andesitic or basaltic flows and locally fragmental rocks, subordinate clastic strata and carbonate, and the metamorphosed and deformed equivalents of these rocks.
Graphitic slate assigned to unit contains Late Triassic fossils near Juneau (Brew and Grybeck, 1984, p.31), and marble intercalated with metavolcanic rocks contains Permian and Permian (?) fossils near Juneau, along coast southeast of Juneau, and in Endi
TrOsv
Clastic sedimentary rocks, subordinate mafic to felsic volcanic rocks, thin- to thick-bedded gray carbonate, chert, and minor ultramafic rocks that have been regionally metamorphosed to slate, phyllite, greenschist, schist, gneiss, and marble in many are
Triassic to Ordovician
Devonian fossils were recovered from marble in the Gambier Bay Formation
CClastic sedimentary rocks, subordinate mafic to felsic volcanic rocks, thin- to thick-bedded gray carbonate, chert, and minor ultramafic rocks that have been regionally metamorphosed to slate, phyllite, greenschist, schist, gneiss, and marble in many ar
TrPsv
Andesitic to basaltic pillow flows, breccia, and tuff; felsic tuff; graywacke, mudstone, shale, chert, conglomerate, and carbonate; and the metamorphic equivalents of these strata.
Triassic and Permian
JMsv
Diverse assemblage of sedimentary and volcanic rocks and their metamorphic equivalents.
Jurassic to Mississippian
KPsvc
Clastic sedimentary, volcanic, and carbonate rocks
Unnamed fossiliferous argillite of Cretaceous age; variably metamorphosed chert, tuffaceous sandstone, felsic tuff, argillite, and light-gray, thin-bedded limestone of Mesozoic or Paleozoic age; highly sheared metasedimentary, metavolcanic, and granodior
Unnamed fossiliferous argillite of Cretaceous age
Pc
Greenschist-facies, massive to thin-bedded marble; medium-bedded dolomite, limestone, and subordinate gray chert beds and nodules; and unnamed fossiliferous gray limestone, cherty limestone, and limestone conglomerate.
Permian
Unnamed fossiliferous gray limestone, cherty limestone, and limestone conglomerate of Permian age northeast of Glacier Bay (Brew and others, 1978) and along west shore of Lynn Canal (Lathram and others, 1959; Brew and Ford, 1985).
Ps
Black argillite, graywacke, calcareous siltstone, chert, and minor basaltic rocks, limestone, and conglomerate.
Pv
Lower Permian basalt (part of the Halleck Formation) on northern Kuiu Island (Muffler, 1967) and unnamed Permian basaltic (?) rocks northeast of Glacier Bay (Brew and others, 1978).
PPasy
Syenite
Syenite on Sukkwan Island that contains biotite +/- amphibole +/- aegerine +/- augite.
Permian and (or) Pennsylvanian
Yielded potassium-argon apparent ages of Early Permian (hornblende) and Late Pennsylvanian (biotite) (Eberlein and others, 1983)
MDsv
Tuffaceous argillite and graywacke and subordinate chert, limestone, and andesitic volcanic rocks.
Mississippian and Devonian
Fossils are Late Devonian and Early and Late Mississippian in age (Jones and others, 1981).
Pac
Massive limestone and minor dolomite containing light-gray chert nodules, and unnamed, medium-bedded to massive crinoidal limestone.
Pennsylvanian
Unnamed, medium-bedded to massive crinoidal limestone on northern Kuiu Island (Brew and others, 1984).
Pas
Middle and Lower Pennsylvanian sandstone and siltstone containing minor limestone and chert-pebble conglomerate (Klawak Formation).
PaDsv
Saginaw Bay Formation on Kuiu Island. From youngest to oldest, unit consists of silty limestone, calcareous chert and limestone, black chert, and massive aquagene tuff and pillow breccia (Muffler, 1967).
Pennsylvanian to Devonian
Volcanic rocks yielded earliest Late to latest Early Devonian conodonts (Dutro and others, 1981; Brew and others, 1984).
Mc
Thin- to thick-bedded, dark-gray limestone, subordinate beds and nodules of light-gray chert, and minor shale and gypsum.
Mississippian
DOc
Carbonate rocks that were metamorphosed to thin- to thick-bedded, dark-gray to white marble.
Devonian to Ordovician
TrOc
Carbonate rocks regionally metamorphosed to gray marble.
Fossils of Pennsylvanian (?) or Permian (?), Paleozoic (?), and Devonian (?) or Silurian (?) age were recovered from unit west of Haines (MacKevett and others, 1974) and fossils of probable Mississippian age were recovered from marble in associated Trias
Scg
Conglomeratic rocks
Polymictic pebble and cobble conglomerate and subordinate sedimentary breccia, olistostromal deposits, sandstone, graywacke, mudstone, and limestone. Clasts consist of porphyritic andesite, limestone, graywacke, mudstone, granitic to gabbroic intrusive r
Silurian
Ss
Graywacke and mudstone turbidites and subordinate olistostromal deposits, layers, and lenses of limestone, and conglomerate.
SOsv
Mudstone and graywacke turbidites, basaltic and andesitic volcanic rocks, and metamorphic equivalents of these strata.
Silurian and Ordovician
SOsv?
SOs
Mudstone and graywacke turbidites, subordinate conglomerate, sandstone, and shale, and minor limestone, chert, and basalt flows and breccia.
SOs?
SOv
Basaltic pillow flows, pillow breccia, and aquagene tuff; massive andesite pyroclastic breccia; felsic breccia and tuff; subordinate interbeds of mudstone and graywacke turbidites and metamorphic equivalents of these strata.
Sst
Syenite and trondhjemite
Leucocratic biotite +/- aegerine +/- arfvedsonite +/- garnet syenite and subordinate leucodiorite; biotite and hornblende trondhjemite); and undivided biotite and (or) hornblende syenite and trondhjemite.
Silurian age indicated by a minimum potassium-argon apparent age on Chichagof Island (Lanphere and others, 1965) and by uranium-lead (zircon) apparent ages of rocks from Annette, Gravina, and Prince of Wales Islands and mainland to southeast (Gehrels and
Sv
Mafic to intermediate volcanic breccia, agglomerate, and flows and greenschist and greenstone derived from these rocks.
SOum
Pyroxenite, hornblendite, and related ultramafic rocks.
Silurian Ordovician
The intrusive body on Dall Island yielded a Late Ordovician potassium-argon (hornblende) apparent age (M.A. Lanphere, written commun., 1984). An Early Silurian potassium-argon (biotite) apparent age has been determined on the body on east-central Prince
SOsvc
Clastic sedimentary, volcanic, and carbonate rocks, undivided
Interbedded graywacke, mudstone, mafic to felsic volcanic rocks, and limestone that have been regionally metamorphosed as high as greenschist facies (Gehrels and Saleeby, 1987b; G.E. Gehrels, unpub. data, 1984).
Dsv
Siltstone, shale, volcanogenic graywacke, conglomerate, and minor limestone that are interbedded with basaltic pillow flows, breccia, and aquagene tuff. Unit consist of the Coronados Volcanics (Devonian), the Devonian (?) St. Joseph Island Volcanics, and
Devonian
Dsv?
DSc
Thin, discontinuous, unfossiliferous limestone layers associated with Devonian and Silurian volcanic rocks (DSv) in the Chilkat Range (Lathram and others, 1959; Brew and Ford, 1985)
Devonian and Silurian
Dcg
Conglomerate and sedimentary breccia interbedded with sandstone, siltstone, shale, and minor graywacke, limestone, and volcanic rocks. Sedimentary structures and presence of red beds and thick sections of coarse conglomerate suggest that strata in Prince
Dc
Thin-bedded to massive, gray limestone and minor shale interbeds.
Ds
Siltstone, shale, sandstone, graywacke, and subordinate limestone breccia, arkose, conglomerate, and volcanic rocks.
DSsc
Limestone, sandstone, calcareous mudstone, and polymictic conglomerate.
Sc
Massive, thin- to thick-bedded, locally reefoidal, light-gray limestone and subordinate shale and polymictic conglomerate.
Loney and others (1975) report that limestone in the Chilkat Range is lithically similar to the Kennel Creek Limestone and contains similar fossils.
DSv
Volcanic rocks found in a fault slice on northern Kuiu Island, basaltic and (or) andesitic rocks in Glacier Bay; and unnamed basalt and andesite in the Chilkat Range.
DSv?
Dv
Basaltic and subordinate andesitic pillow flows, breccia, aquagene tuff, and minor sedimentary interbeds.
Dv?
DOsv
Graywacke, mudstone, shale, limestone, and subordinate mafic to intermediate volcanic rocks that have been metamorphosed in most areas to hornfels, slate, phyllite, schist, amphibolite, marble, gneiss, and granofels.
Graywacke, mudstone, shale, limestone, and subordinate mafic to intermediate volcanic rocks that have been metamorphosed in most areas to hornfels, slate, phyllite, schist, amphibolite, marble, gneiss, and granofels.  (Where shown having a stippled overp
DOsv?
SOq
Quartz diorite
Late and Middle Ordovician diorite and quartz diorite and Early Silurian to Late Ordovician biotite quartz monzonite; Early Silurian to Late Ordovician diorite, quartz diorite, and their metamorphosed and deformed equivalents; and layered and foliated qu
SOq?
Ogb
Hornblende gabbro, and subordinate hornblende pyroxenite and hornblendite on Sukkwan Island, and metagabbro on southern Dall Island.
Ordovician
Hornblende gabbro and subordinate hornblende pyroxenite and hornblendite on Sukkwan Island that yielded a Middle Ordovician potassium-argon apparent age (Eberlein and others, 1983).
Ogb?
Cdg
Diorite and granodiorite
Foliated and metamorphosed hornblende diorite and biotite +/- hornblende granodiorite.
Cambrian
Foliated and metamorphosed hornblende diorite and biotite +/- hornblende granodiorite on east-central Prince of Wales Island and on southern Gravina Island that yielded Late and Middle Cambrian preliminary uranium-lead (zircon) apparent ages (Gehrels and
pOmsv
Metasedimentary and metavolcanic rocks
Metasedimentary and metavolcanic rocks derived from pre-Ordovician basaltic to andesitic pillow flows, pillow breccia, and tuff breccia, volcanoclastic graywacke and mudstone, and minor limestone and felsic volcanic breccia and tuff during regional green
pre-Ordovician
Radiometric age constraints suggest that metamorphism occured during Early Ordovician to Middle Cambrian time (Turner and others, 1977; Gehrels and Saleeby, 1987a, b; M.A. Lanphere, oral commun., 1984).
pOmc
Metacarbonate rocks
Metacarbonate rocks derived from pre-Ordovician carbonate rocks during regional greenschist- and local amphibolite-facies metamorphism. Found as thin to thick marble layers and lenses intercalated with pre-Ordovician metasedimentary and metavolcanic rock
pTmsv
Metasedimentary and metavolcanic rocks derived from pre-Tertiary sedimentary and volcanic rocks during regional amphibolite- and local granulite-facies metamorphism. Common rock types include pelitic, semipelitic, and quartzofeldspathic schist and gneiss
pre-Tertiary
pTmsv?
pTmc
Metacarbonate rocks derived from pre-Tertiary carbonate rocks and carbonate-rich clastic strata during regional amphibolite- and local granulite-facies metamorphism. Found as discontinuous marble lenses, as thick continuous marble layers, and as calc-sil