QTwd
Dikes, Hypabyssal and plutonic rocks
Pleistocene, Pliocene, Miocene, or Oligocene
Chiefly andesite and dacite
Richter, D.H., Preller, C.C., Labay, K.A., and Shew, N.B., 2005, Geology of Wrangell-Saint Elias National Park and Preserve, southcentral Alaska:  U.S. Geological Survey Scientific Investigations Series Map SIM-2877, scale 1:350,000.
bu
Bedrock of unknown type or age
Areas that air photo interpretation suggest as being underlain by bedrock.  Typically are of higher elevation than surrounding glacial deposits and show hints of structure.  Also includes rubble of metasiltstone and chert in the Kantishna River quadrangl
Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix.
Qs
Surficial deposits, undifferentiated
Quaternary
Unconsolidated silt, sand, and gravel of fluvial, glacial, colluvial, and other origins
Qa
Alluvium
Holocene
In active streambeds and lowest terraces along larger streams and active alluvial fans.  Chiefly well sorted gravel and sand; minor silt and boulders
Qu
Slope deposits, undifferentiated
Holocene and Pleistocene
Colluvium consisting of talus and small landslides, also includes small glacial, rock glacier, and alluvial deposits.  Sand, gravel, boulders, diamicton, and rubble
Qcb
Bluff colluvium
Occurs along high steep bluffs of the Copper River and its principal tributaries.  Locally includes small areas of the Copper River deposits (Qcr) and the drift of older glaciations (Qg).  Unsorted silt, sand, gravel, and boulders
Ql
Landslide deposits
Slumps, earth-debris flows, block glides, and debris avalanches.  Diamicton and rubble
Qao
Older alluvium
In higher terraces along larger streams and in inactive alluvial fans.  Predominantly of Pleistocene age, but may include localized Holocene deposits.  Chiefly well sorted gravel and sand; minor silt and boulders
Qfl
Fine-grained deposits
In ponds, swamps, lagoons, and along low-gradient streams.  Chiefly silt, clay, fine sand, peat, and other organic material
Qb
Beach and delta deposits
Wave-deposited, coarse-grained material and driftwood along seacoast; fine-grained sediment in mud flats of Copper River Delta; and marine uplift terraces.  Successive spit-building episodes of progressive gradation are preserved in beach sequences along
Qms
Mineral spring deposits
Deposited by warm, Na-HCO3-rich, CO2-charged, saline spring waters forming the Klawasi Group (Shrub, Upper Klawasi, and Lower Klawasi mud volcanoes) (Motyka and others, 1989) located west of Mount Drum.  Also includes one or more inactive deposits west o
Qe
Eolian deposits
Dunes on tops of river bluffs, windblown flats, and river bars.  Includes informally named Bremner sand dunes, a large barchan field, located at confluence of Bremner and Copper Rivers.  Fine-grained sand
Qcr
Copper River deposits
Pleistocene
Interbedded glaciolacustrine, glacial, and alluvial deposits.  Includes deposits of glacial Lake Atna (Nichols, 1989; Williams and Galloway, 1986); historically complex basin built from numerous lake stages in response to multiple glacial advances and re
Superglacial drift
Superglacial drift on present day glaciers.
Qrg
Rock glacier deposits
Well-defined lobate forms that may include glacier ice cores.  Chiefly blocks of rubble
Qag
Drift of Alaskan glaciation
Neoglacial deposits of end, lateral, and ground moraines, kames and outwash proximal to present glaciers; includes small rock glaciers.  Diamicton, local gravel, and sand
Qg
Drift of older glaciations
Wisconsin glaciation and older end, lateral, and ground moraines local kames, kame-like deposits, and outwash.  Also includes the glaciolacustrine deposits (Qcr) near complex interface with glacial Lake Atna in lower Chitina River valley.  Chiefly diamic
Qwws
Shield lavas, Mount Wrangell volcano
Holocene and Pleistocene, 0.65 Ma and younger
Chiefly andesitic flows.  Hundreds of voluminous andesitic lavas flowed for 650,000 years, concluding 25,000 years ago; one or two undated flows might be younger
Qwwv
Valley-fill lavas, Mount Wrangell volcano
Lavas filled deeply incised glacial valleys cutting into the thick shield lavas (Qwws).  A few far-reaching flows interbedded with the Copper River deposits (Qcr); chiefly andesite
Qwd
Lava flows, Mount Drum volcano
Pleistocene, 0.6-0.2 Ma
Andesite and dacite flows; dikes.  Constructed during andesitic cone( or shield) building and rhyolite-dacite ring dome emplacement cycles.  A late (0.25 Ma) cataclysmic eruption destroyed top and south sides
Qwc
Shield and intracaldera lavas, Capital Mountain volcano
Pleistocene, 1.0 Ma
Chiefly andesite. Small andesitic shield and summit caldera intruded at center by an andesite plug, focal point of a spectacular radial basaltic andesitic dike swarm
Qvd
Volcanic debris flows
Chetaslina volcanic mass-flow deposit, probably sourced from Mount Drum, exposed along Chetaslina and Copper Rivers; Sanford volcanic debris flow exposed along Sanford and Copper Rivers.  Large blocks of lava and varied debris
Qpf
Pyroclastic flows
The extensive informally named Nadina hot avalanche deposit resulting from Mount Drum's cataclysmic eruption and a smaller pyroclastic flow (0.3 Ma) possibly derived during an explosive episode from Mount Drum deposited at Chetaslina River's two forks.
Qws
Lava flows, Mount Sanford volcano
Pleistocene, 0.9-0.5 Ma
Chiefly andesite and dacite. Height and extensive ice cover limit understanding of volcanic structure.  Edifice, apparently sourced from three major vents, is an intermingled complex of lava flows and domes, predominantly andesite
Qbc
Cinder cones, flows, and tuffs
Olivine basalt and basaltic andesite
Qwj
Shield and intracaldera lavas, Mount Jarvis volcanoes
Pleistocene, 1.7-1.0 Ma
Extensive flat-lying andesitic flows.  North-trending linear succession of centers including at least two summit calderas and eroded andesitic shields; satellite dacite domes and flows
Qwdr
Domes, Mount Drum volcano
Dacite and rhyolite domes; associated flows and dikes
Qwsr
Rhyolite dome and flow, Mount Sanford volcano
Thick far-ranging flow (0.6 Ma) probably sourced from northeast flank dome
Qwjd
Domes, Mount Jarvis volcanoes
Final stage deposition at chain's north end; dacite
Qwcr
Central andesite plug, rhyolite laccolith and dike, Capital Mountain volcano
Plug represents final activity; dike originated from laccolith on shield's southeast flank
QTwt
Shield and intracaldera lavas, Tanada Peak volcano
Pleistocene and Pliocene, 1.8-0.9 Ma
Andesite flows and local agglutinates.  Large shield and remnant summit caldera, stripped by erosion, remaindered to thick, massive intracaldera lavas as serrated topographic highs
QTwi
Flows of the Ice Fields Plateau, Older volcanic and sedimentary rocks
Pleistocene, Pliocene, or Miocene
Massive dacite and high-silica andesite lavas capping Ice Fields Plateau east of Nabesna Glacier
QTw
Lava flows and sedimentary rocks, Older volcanic and sedimentary rocks
Flat-lying andesite and dacite lava flows; a Tertiary tillite and the fossil-rich conglomeratic sandstone Frederika Formation.  Boomerang (<1.0 Ma), Chetaslina (1.6-0.8 Ma), Skookum Creek (3.2-2.0 Ma), Mount Blackburn (4.3-3.2 Ma), and other Early Quater
QTwr
Domes and intrusive rocks, Older volcanic and sedimentary rocks
Chiefly dacite and rhyolite
QTy
Yakataga Formation
Holocene(?), Pleistocene, Pliocene, and Miocene
Mudstone, siltstone, sandstone, and diamictite in a diverse marine and glacio-marine clastic continental shelf deposit.  Abundant mega- and micro-fauna
Tps
Poul Creek Formation
early Miocene(?, Oligocene, and late Eocene(?)
Concretionary marine siltstone, claystone, sandstone, and conglomerate, minor basaltic tuff, and locally glauconitic.  Includes part of the clastic Redwood Formation and, as mapped, forms part of Robinson Mountains north of Cape Yakataga
Tt
Tokun Formation
Eocene
Shallow marine concretionary siltstone and minor sandstone
Tk
Kulthieth Formation
Eocene and early Paleocene(?)
Interbedded nonmarine carbonaceous sandstone, siltstone, shale, and minor coal; sparse warm-water marine molluscan megafauna and locally abundant subtropical plant fossils.  Includes small occurrences of the siltstone-rich Stillwater Formation east of St
Tos
Turbidites, Orca Group
early Eocene and late Paleocene
Mudstone to sandstone, locally fossil rich, submarine gravity flows.  Weakly metamorphosed flysch and basalt thick submarine fan complex
Tp
Younger plutons
Tertiary
Hornblende-feldspar and feldspar porphyry plutons; in part, related to Wrangell volcanism.  K-Ar dates indicate ages of 39-17 Ma
Tw
Lava flows and lahars, Oldest volcanic rocks
Miocene or Oligocene
Basaltic andesite, andesite, and dacite lava flows; andesitic lahar deposits.  Sonya Creek (23-20 Ma) and other, unmapped, older Tertiary volcanic centers (26-23 Ma)
Twr
Rhyolite flow, Oldest volcanic rocks
Obsidian-bearing lava within Sonya Creek caldera
Twd
Domes, Oldest volcanic rocks
Dacite and rhyolite underlying the lava flows and lahar deposits (Tw) of Sonya Creek volcano
Tm
Volcanic and hypabyssal rocks
Miocene and Oligocene
Basalt to andesitic plugs, dikes, and flows
Td
Rhyolite porphyry and granite
Pliocene(?) or Miocene(?)
Discordant hypabyssal plutons and dikes exposed between Mount Augusta and Mount Cook
Tov
Basalt, Orca Group
Mainly tabular bodies of pillowed, massive, and columnar jointed tholeiitic basalt lava flows; locally interbedded minor mudstone and siltstone.  Weakly metamorphosed flysch and basalt thick submarine fan complex
Orca Group, Basalt
Mainly tabular bodies of pillowed, massive, and columnar jointed tholeiitic basalt lava flows; locally interbedded minor mudstone and siltstone
Th
Shallow plutons, small stocks, dikes, and sills
Andesite to dacite porphyry, diorite, and quartz diorite.  K-Ar dates indicate ages range from 7.0 to 3.0 Ma, younger than the plutons (Tp) located on north side of Wrangell Mountains.  Probably related to Wrangell volcanism, porphyry rocks may be hypaby
Tg
Granodiorite
Plutonic phase of the Wrangell Lava exposed mainly at Hawkins Glacier head, marginal to Mount Blackburn volcano caldera
Tgp
Granitic plutons
Eocene, 50 Ma
Granite, granodiorite and diorite intruding Chugach and Prince William terranes; intermediate composition Eocene age dikes not drawn on map
Tsq
Snag pluton
Tertiary, 50 Ma
Informally named body of leucocratic biotite quartz monzonite.  K-Ar date indicates age of 50 Ma
Tc
Metamorphic complex of Cottonwood Creek of Richter (1976)
Banded granite and quartz diorite gneiss enclosed in schist and phyllite, most likely part of the Devonian metasedimentary (Dp) rocks.  Greenschist to amphibolite metamorphism yields metamorphic age of 20-17 Ma.  Complex occurs within Denali Fault System
Ku
Marine sedimentary rocks
Early and Late Cretaceous
Sandstone and siltstone deposited at shallow to moderate depths; locally abundant marine fossils.  Includes the MacColl Ridge, Chititu, Schulze, and Moonshine Creek Formations
Kun
Nonmarine sedimentary rocks
Late Cretaceous
Conglomerate, sandstone, siltstone, and mudstone locally containing abundant plant fossils
Kl
Shallow marine sedimentary rocks
Early Cretaceous
Conglomerate, sandstone, siltstone, and clastic sandy limestone deposited under nearshore, high-energy, transgressive marine conditions; locally, concretions and abundant fossils.  Includes the Kennicott, Kuskulana Pass, and Berg Creek Formations
KJm
Mélange units, Valdez Group
mid-Cretaceous, Jurassic(?), and Late Triassic
Tholeiitic pillowed basalt, chert, tuff, greywacke, argillite, and phyllite-greenstone deposited along a convergent plate margin as early as Late Triassic continuously into middle Cretaceous.  Includes the McHugh Complex, a structurally complex and chaot
Kc
Chisana Formation
Thick volcanic arc assemblage of marine and subaerial volcanic and volcaniclastic rocks.  Younger part consists of andesite and basaltic andesite flows, and volcaniclastic rocks; older part consists of volcaniclastic rocks and locally fossil rich marine
MzPzu
Alpine-type ultramafic rocks and gabbro
Cretaceous(?, Jurassic(?, Triassic, Permian, and Pennsylvanian(?
Serpentinized peridotite and dunite, locally containing chromitite, leucocratic gabbro, and hornblende gabbro
Kg
Mid-Cretaceous plutons
Cretaceous
Chiefly discordant plutons of granodiorite and quartz monzonite; also include quartz diorite, diorite, syenodiorite, and trondhjemite phases.  K-Ar dates indicate ages of 117-105 Ma.  Locally abundant xenoliths
Kv
Greenschist-facies flysch, Valdez Group
Mainly mudstone and graywacke turbidite beds, carbonaceous phyllite, minor mafic tuff and breccia in a thick regionally extensive belt of accreted flyschoid deep marine rocks.  Flysch metamorphosed to lower greenschist-facies
Kvv
Metamorphosed basalt and tuff, Valdez Group
Tholeiitic metabasalt and basaltic meta-tuff, local pillow lava and pillow breccia, gabbroic dikes and sills
Kvm
Amphibolite-facies flysch, Valdez Group
Mainly mudstone and graywacke turbidite beds, carbonaceous phyllite, minor mafic tuff and breccia in a thick regionally extensive belt of accreted flyschoid deep marine rocks.  Flysch metamorphosed to amphibolite-facies schist
Kvg
Gneiss and schist, Valdez Group
Gneiss, banded and migmatite.  Includes the amphibolite-facies schist of Mount Augusta of Plafker (written commun., 2000).  Mainly mudstone and graywacke turbidite beds, carbonaceous phyllite, minor mafic tuff and breccia in a thick regionally extensive
KJs
Nutzotin Mountains sequence of Berg and others (1972)
Early Cretaceous and Late Jurassic
Argillite-graywacke graded beds and minor conglomerate, sandstone, and limestone; forming thick deep ocean trench fossil-poor marine flysch sequence bordering Wrangellia terrane
Mzc
Conglomerate and sandstone
Early Cretaceous(? and Late Jurassic(? or older
Pebble to boulder conglomerate and coarse-grained sandstone.  May reflect the Nutzotin Mountains sequence (KJs) of Berg and others (1972) northern shore facies; hornfels alteration along southern contact of the Snag pluton (Tsq)
Kyf
Flysch, Yakutat Group
Cretaceous and Jurassic(?)
Graywacke, siltstone, and argillite.  Complexly deformed flysch and mélange locally recrystallized to greenschist
Kym
Mélange, Yakutat Group
Discrete blocks of greenstone, limestone, marble, graywacke, chert, conglomerate, and plutonic rocks, up to several kilometers in greatest dimension, in a sheared matrix of mudstone.  Complexly deformed flysch and mélange locally recrystallized to greens
Kyn
Schist of Nunatak Fiord
Complexly deformed interbedded mudstone and sandstone, minor volcaniclastic rocks and conglomerate; metamorphosed to greenschist- and epidote-amphibolite facies.  Crops up between Boundary and Fairweather Fault Systems and intruded extensively by the Ter
Js
Sedimentary rocks
Late, Middle, or Early Jurassic
Chiefly spiculite, graywacke, mudstone, and conglomerate deposited in a shallow-marine and nearshore littoral setting.  Includes the fossil-rich Lubbe Creek, Nizina Mountain, and Root Glacier Formations
Jk
Kotsina Conglomerate
Conglomerate and minor sandstone deposited under rapid local marine circumstances during orogenesis.  Fossils absent
JTrt
Talkeetna Formation
Early Jurassic and Late Triassic(?
Dominantly andesitic volcaniclastic rocks, products of Late Triassic and Early Jurassic oceanic volcanic arc
Jnt
Mafic and ultramafic rocks
Middle or Early Jurassic
Gabbro, pyroxenite, peridotite and dunite.  Includes the Nelchina River Gabbronorite, the Tonsina ultramafic, and a mafic sequence of Winkler and others (1980).  K-Ar dates indicate ages of 188-171 Ma
Jc
Chitina Valley batholith
Late Jurassic
Compositionally diverse quartz monzodiorite, ranging from granite to diorite, generally foliated and locally gneissic particularly within plutons enclosed by the Strelna Metamorphics of Plafker and others (1989) (PPasm).  K-Ar dates indicate plutonic age
Jlc
Schist of Liberty Creek of Winkler and others (1981)
Jurassic(?
Basalt flows, breccia, and tuff; regionally metamorphosed greenschist- and blueschist-facies Middle Jurassic or older oceanic assemblage protolith
JTrm
McCarthy Formation
Early Jurassic and Late Triassic
Spiculite, impure chert and limestone, and shale deposited in a starved marine basin environment.  Fossils locally abundant
Trl
Triassic limestone
Late Triassic
Locally fossil-rich, thin-bedded limestone and interbedded argillite in partially starved marine basin; overlies shallow marine to intertidal fossil-poor cherty massive limestone
Trcn
Chitistone and Nizina Limestones
Chiefly limestone and dolomite; minor chert and marble; locally fossil rich.  The upper Chitistone and cherty Nizina deposited in a shallow to moderately deep marine neritic environment; transition into an intertidal-supratidal setting with local sabkha
PPadm
Diorite complex, metamorphic part
Permian(?) and Pennsylvanian
Amphibolite-grade metamorphic rocks of mainly quartz-feldspar schist, biotite-hornblende gneiss, and syenite-monzonite gneiss.  Jurassic K-Ar ages in probability reflect a metamorphic age.  Together with associated late Paleozoic plutons (PPadp) construc
Trn
Nikolai Greenstone
Late and(or Middle Triassic)
Widespread sequence of tholeiitic flood basalt flows, mainly subaerial and characteristically amygdaloidal; subordinate volcaniclastic interbeds and volcanic conglomerate basal sections.  Metamorphosed to prehnite-pumpellyite facies although alteration r
PPasm
Strelna Metamorphics of Plafker and others (1989)
Jurassic(?), Triassic(?), Permian, Early Pennsylvanian, and Late Mississippian(?)
Dominantly calcareous metasedimentary rocks, schist, phyllite, amphibolite, and marble; lesser quartzite, meta-andesite, and metabasalt in thin to thick thrust sheets containing local pods of the tectonically emplaced ultramafic rock and marble (PPam); o
PPas
Skolai Group, undivided
Early Permian and Pennsylvanian
Lower late Paleozoic magmatic arc and associated upper sedimentary rocks.  Equivalent to the Mankomen Group (Pe, Pel, and PPass) and the Tetelna Volcanics (PPat) in northern Wrangell Mountains and eastern Alaska Range
Pago
Gabbro and orthogneiss
Pennsylvanian
Interlayered hornblende pyroxene gabbro and monzonitic gneiss; overlain by the Skolai Group (PPas, Ph, Pl, and PPasc) and their metamorphosed equivalent, the Strelna Metamorphics of Plafker and others (1989) (PPasm).  Represents, in part, Pennsylvanian o
Jurassic(?, Triassic(?, Permian, Early Pennsylvanian, and Late Mississippian(?)
PPass
Slana Spur Formation, Mankomen Group
Fossil-rich volcanic sandstone, siltstone, conglomerate, and impure bioclastic limestone; shed off the Tetelna volcanic arc (PPat)
Pzvc
Metavolcaniclastic rocks, Metamorphic rocks of the Carden Hills
Permian(?, Pennsylvanian, Mississippian, and Devonian(?)
Chiefly metasandstone, metatuff, and quartzite; greenschist-facies metamorphism
Pzv
Metavolcanic rocks, Metamorphic rocks of the Carden Hills
Slightly porphyritic meta-andesite and metabasalt; greenschist-facies metamorphism
Ph
Hasen Creek Formation
Early Permian
Fossil-rich marine argillite, shale, and sandstone; nonvolcanic origin
Pl
Limestone of the Hasen Creek Formation
Fossil-rich, lenticular, marine limestone; partially equivalent to the Strelna metamorphic marble of Plafker and others (1989)
Pel
Limestone of Eagle Creek Formation, Mankomen Group
Fossiliferous thin- to thick-bedded limestone
Pam
Monzonite-granite complex
Large composite granite and quartz monzonite pluton containing lesser monzonite, syenite, and gabbro emplaced between Wrangellia and Alexander(? terranes.  K-Ar dates indicate ages of 297-295 Ma.  Correlates with the Ahtell pluton (Paa) in northern Wrang
Paa
Ahtell pluton
Quartz monzonite and granodiorite discordant zoned pluton.  Together with the monzonite-granite complex (Pam) in Saint Elias Mountains make part of the Skolai-Tetelna magmatic arc's (PPat, PPas, and PPasc) core.  K-Ar data indicates an age of 285 Ma
PPadp
Diorite complex, plutonic part
Permian(? and Pennsylvanian
Hornblende diorite grading into gneissic diorite.  Together with associated metamorphics (PPadm), almost certainly represents roots of the Skolai-Tetelna magmatic arc's (PPat, PPas, and PPasc) roots.  Possibly correlative with the gabbro and orthogneiss
Pe
Eagle Creek Formation, Mankomen Group
Nonvolcanogenic argillite and siltstone deposited in a moderately deep quiet basin.  Abundant fossils, cone-in-cone structures, and concretions.  Intruded by locally abundant Triassic gabbroic inclusions (Trn) and porphyry dikes and sills (Tp)
PPzm
Marble
Permian and Early Pennsylvanian
Regionally metamorphosed with poorly preserved and locally placed Permian and Early Pennsylvanian fossils.  Partially equivalent to the Permian limestone of the Hasen Creek Formation (Pl)
PPasc
Station Creek Formation
Magmatic arc consists of a younger volcaniclastic member and an older andesitic and basaltic lava flow member, both of submarine origin; locally metamorphosed to greenschist-facies south of Chitina Fault
PPat
Tetelna Volcanics, Mankomen Group
Subaerial and submarine basaltic to dacite lava, lahar flows, tuff deposits, and fine-grained volcaniclastic rocks.  Extensive late Paleozoic magmatic arc vestiges form Wrangellia terrane's basement in northern Wrangell Mountains and eastern Alaska Range
Pzk
Kaskawulsh Group of Kindle(1953)
Pennsylvanian, Mississippian, Devonian(?, and older
A metamorphosed marine sequence of marble, schist, and phyllite; minor meta-tuff, flows, breccia, and meta-conglomerate; probably oceanic crustal progression with carbonate reefs.  Poorly preserved Ordovician, Devonian, and possible Mississippian and Pen
Dp
Metasedimentary rocks
Devonian
Mainly phyllite, also includes calcareous mica-schist, quartzite, metaconglomerate, and thin marble lenses.  Greenschist-facies metamorphism.  Contains poorly preserved Devonian fossils