Qtf
Modern tidal flat and estuarine deposits
Quaternary, Holocene
Well-sorted, sub-tidal, stratified silt and some sand and local gravel deposited in shallow embayments
Wilson, F.H., and Hults, C.P., in press, Geology of the Prince William Sound and Kenai Peninsula region, Alaska; Including the Kenai, Seldovia, Seward, Blying Sound, Cordova, and Middleton Island 1:250,000-scale quadrangles:  U.S. Geological Survey Scien
Qs
Unconsolidated surficial deposits, undivided
Quaternary
Mainly unsorted boulders, cobbles, gravel, sand, and silt produced, deposited, and reworked by action of wind, water, glaciers, and frost, including solifluction.  Includes deposits of present streams, colluvial and alluvial fans; glaciofluvial, glaciola
Qat
Alluvial and terrace deposits
Flood-plain alluvium and stream terrace deposits.  Consists of poorly- to well-sorted silt, sand, pebbles, cobbles, and boulders.  Also includes abandoned channel deposits in outwash above modern floodplains or underfit stream channels, inferred to be re
Qls
Landslide and colluvial deposits
Unsorted, angular rock debris and mud in slumps, earth-debris flows, block glides, and debris avalanches, and poorly- to well-sorted silt to boulders in alluvial fans and cones, and unsorted rock talus (Riehle and Emmel, 1980; Waythomas and Miller, 1999;
Qsl
Lacustrine, swamp, and fine silt deposits
Chiefly silt, clay, fine sand, peat, and other organic material generally of lacustrine origin (Riehle and Emmel, 1980; Richter and others, 2005; F.H. Wilson, unpub. data)
Qb
Beach deposits
Sand, gravel, and cobbles of present and former beaches, beach ridges, spits, and tidal flats (Tysdal and Case, 1979; Winkler and Plafker, 1993; Detterman and Hartsock, 1966; Riehle and Emmel, 1980; F.H. Wilson, unpub. data).  Wave-deposited, coarse-grai
Qes
Estuarine deposits
Fine-grained silt rich in organic material, mud, and peat (Winkler and Plafker, 1993).  Includes salt-marsh deposits of Detterman and Hartsock (1966) and grades into tidal flat deposits (Riehle and Emmel, 1980; F.H. Wilson, unpub. data).  Also includes m
Qd
Eolian deposits
Dunes consisting of well sorted, fine-grained sand and silt aligned in longitudinal ridges on the Cooper River delta (Winkler and Plafker, 1993).  Also includes dunes on top of river bluffs, windblown flats, and river bars (Richter and others, 2005).  In
Qdl
Deltaic deposits
Deltaic deposits, including outwash and alluvial deposits (F.H. Wilson, unpub. data)
Qgl
Glaciolacustrine deposits
Largely ephemeral glacial lake and lake-related deposits.  Well-sorted, well-stratified clay, silt, and fine sand deposited in ephemeral glacial and postglacial lakes.  Thought to be typically covered by several feet of muck and peat (F.H. Wilson, unpub.
Qm
Glacial deposits
Glacial drift consisting of sand, gravel, and boulders.  Includes ground, recessional, end, medial, and lateral moraine deposits; as well as colluvium, talus, landslide debris, alluvium, and silt, locally (Riehle and Emmel, 1980; F.H. Wilson, unpub. data
Qag
Drift of Neoglacial age
Neoglacial terminal, recessional, lateral, and ground moraine consisting of unsorted boulders, cobbles, gravel and sand deposited during retreat of glaciers.  Includes deposits of the Tunnel and Tustumena Stade (Detterman and Hartsock, 1966); Tunnel Stad
Qao
Outwash of the Neoglacial age
Outwash deposits associated with modern and Holocene glaciers (Karlstrom, 1964; F.H. Wilson, unpub. data).  Consist of poorly- to well-sorted silt, sand, and gravel in terraces and outwash fan plains (Detterman and Hartsock, 1966; Riehle and Emmel, 1980)
Qgn
Glacial deposits of the Naptowne and Brooks Lake Glaciations
Quaternary, Pleistocene
Terminal, recessional, lateral, medial, and ground moraine and other deposits.  Moderately weathered moraine along Cook Inlet shoreline; heavily spruce and brush covered (Detterman and Hartsock, 1966; F.H. Wilson, unpub. data).  Internal contacts on west
Qgno
Outwash and valley train deposits
Silt, sand, and gravel graded to moraines of Naptowne age (map unit Qgn) on the Kenai Peninsula (Karlstrom, 1964) and to Brooks Lake age moraines on the west side of Cook Inlet (F.H. Wilson, unpub. data)
Qog
Older glacial deposits
Included here are the prominent, but modified morainal deposits of the Knik and Eklutna Glaciations.  These deposits are widely exposed north of Homer on the Kenai Peninsula (Karlstrom, 1964).  On the Kenai Peninsula, moraines of Knik and Eklutna age are
Qogo
Outwash associated with older glacial deposits
Silt, sand, and gravel graded to moraines of Knik and Eklutna age on the Kenai Peninsula (Karlstrom, 1964)
Qch
Moraine of the Caribou Hills Glaciation
Highly modified morainal deposits in the Caribou Hills and exposed as remnant deposits elsewhere on the Kenai Peninsula (Karlstrom, 1964).  These deposits are terraced below elevations of about 305 m (1,000 ft) and discontinuously mantled by proglacial l
Tkn
Kenai Group
Tertiary, Pliocene to Oligocene
Coal-bearing clastic unit consisting of, in descending order, the Sterling, Beluga, and Tyonek Formations and Hemlock Conglomerate in the vicinity of Cook Inlet.  According to Calderwood and Fackler (1972) unit is at least 8,000-m-thick in the subsurface
Ts
Sterling Formation
Tertiary, Pliocene and Miocene
Weakly lithified massive sandstone, conglomeratic sandstone and interbedded claystone; includes interbedded lignitic coals typically less than 1-m-thick in the upper part of the unit, but may be as much as 3-m-thick in the lower part of the unit (Calderw
Tb
Beluga Formation
Tertiary, Miocene
Nonmarine, interbedded, weakly lithified sandstone, siltstone, mudstone, carbonaceous shale, coal, and minor volcanic ash (Bradley and others, 1999).  Calderwood and Fackler (1972) reported a distinctive feature of the Beluga Formation is its lack of mas
Tty
Tyonek Formation
Tertiary, Miocene and Oligocene
Nonmarine conglomerate and subordinate sandstone, siltstone, and coal within the map area as described by Bradley and others (1999).  However, in general, the Tyonek Formation is identified by the presence of massive sandstone beds and lignitic to subbit
Th
Hemlock Conglomerate
Tertiary, Oligocene
Sandstone, conglomerate, and siltstone assigned to this unit, as defined by Calderwood and Fackler (1972) occur only in the vicinity of Harriet Point in the Kenai quadrangle on the west side of Cook Inlet.  On the basis of the description in Detterman an
Twf
West Foreland Formation
Tertiary, Eocene and Paleocene
Exposed only on the west side of Cook Inlet, thin unit consists of tan to light-yellow-brown cobble conglomerate interbedded with lesser sandstone, laminated siltstone, and silty shale (Detterman and Hartsock, 1966).  Thin coal beds are interbedded with
Ksm
Saddle Mountain section of Magoon and others (1980)
Upper Cretaceous, Maastrichtian
Nonmarine sandstone, conglomerate, and minor siltstone and coal found northeast of Chinitna Bay in a section 83-m-thick (Magoon and others, 1980).  Consists dominantly of fine- to medium-grained sandstone that becomes finer grained upward.  Unit is gener
Jnp
Naknek Formation, Pomeroy Arkose Member
Upper Jurassic, Kimmeridgian and Oxfordian?
Massive light-gray, medium- to coarse-grained arkose containing many interbedded thin beds of dark-gray to brownish siltstone and pebble conglomerate (Detterman and Hartsock, 1966).  The sandstone is rich in quartz (40-45 percent) and sodic feldspar (30-
Jnst
Naknek Formation, Snug Harbor Siltstone Member
Upper Jurassic, Kimmeridgian and Oxfordian
Dominantly massive to thin-bedded, dark-gray to black siltstone; calcareous gray sandstone beds are minor part of the unit (Detterman and Hartsock, 1966).  Hard gray limestone concretions and lenses are locally abundant; rare thin layers of volcanic ash
Jnn
Naknek Formation, Northeast Creek Sandstone Member
Upper Jurassic, Oxfordian
Light-gray, thin-bedded to massive arkosic sandstone, graywacke, and siltstone.  Originally called the "lower sandstone member" by Detterman and Hartsock (1966) who considered this unit to have only local significance.  Later work on the Alaska Peninsula
Jnc
Naknek Formation, Chisik Conglomerate Member
Upper Jurassic, Tithonian to Oxfordian
Consists of massive to thick-bedded conglomerate and interbedded, crossbedded, quartzose sandstone.  Clasts, as large as 2 m, are mainly granitic rocks, but up to 20 percent metamorphic and volcanic rocks are present (Detterman and others, 1996).  The un
Jcp
Chinitna Formation, Paveloff Siltstone Member
Middle Jurassic, Callovian
Consists of massive dark-gray arenaceous siltstone in the upper part and a thick sandstone unit at its base (Detterman and Hartsock, 1966).  Large ellipsoidal concretions and lenticular beds of limestone occur throughout the unit and thin interbeds of sa
Jct
Chinitna Formation, Tonnie Siltstone Member
Massive dark-gray to brownish-gray arenaceous siltstone, which weathers brownish-gray to red-brown (Detterman and Hartsock, 1966).  Numerous small yellowish-brown weathering limestone concretions occur in parallel bands and randomly throughout the sectio
Jtb
Tuxedni Group, Bowser Formation
Middle Jurassic, Callovian and Bathonian
Heterogeneous assemblage of sandstone, conglomerate, shale and siltstone characterized by rapid facies changes (Detterman and Hartsock, 1966).  Massive light- to dark-gray sandstone and conglomerate are the dominant lithologic types on the Iniskin Penins
Jtt
Tuxedni Group, Twist Creek Siltstone
Middle Jurassic, Bajocian
Soft, poorly consolidated, thin-bedded to massive siltstone and silty shale as much 125-m-thick (Detterman and Hartsock, 1966).  The siltstone is dark-gray, weathers to dark-rusty brown, and contains many thin beds of volcanic ash that weather a bright-o
Jtc
Tuxedni Group, Cynthia Falls Sandstone
Middle Jurassic, Bajocian?
Massive to thick-bedded graywacke sandstone and pebble conglomerate about 200-m-thick (Detterman and Hartsock, 1966).  The sandstone is medium- to coarse-grained, greenish-gray to dark-green, has graded bedding and weathers mottled light-gray due to the
Jtf
Tuxedni Group, Fitz Creek Siltstone
Middle Jurassic, middle Bajocian
Thick sequence (up to 400-m-thick) of massive, bluish dark-gray, arenaceous, coarse- to fine-grained siltstone that commonly weathers rusty orange and contains many small limestone concretions (Detterman and Hartsock, 1966).  Fine-grained sandstone and,
Jtg
Tuxedni Group, Gaikema Sandstone
Middle Jurassic, lower middle Bajocian
Resistant, cliff-forming, massive to thin-bedded graywacke sandstone and cobble conglomerate 150- to 260-m-thick (Detterman and Hartsock, 1966).  Sandstone commonly occurs in graded beds up to 3-m-thick, whereas conglomerate is well-sorted within individ
Jtk
Talkeetna Formation, undivided
Lower Jurassic
Bedded volcanic rocks widely distributed in the Seldovia and Kenai quadrangles west of Cook Inlet.  Where undivided, unit consists of flows, breccia, tuff, and agglomerate and locally interbedded minor sandstone and shale, all typically somewhat altered
Jtkh
Talkeetna Formation, Horn Mountain Tuff Member
Bedded tuff and tuffaceous feldspathic sandstone, locally containing porphyritic andesite flows.  Bedded tuff is tan, red, green, purple, or mottled-color, thin-bedded to massive and fine- to coarse-grained (Detterman and Hartsock, 1966).  Locally, tree
Jtkp
Talkeetna Formation, Portage Creek Agglomerate Member
Reddish fragmental volcanic debris, primarily rounded volcanic bomb-like fragments and lapilli tuff grading to fine-grained tuff, clastic sedimentary rocks and flows northward in the map area (Detterman and Hartsock, 1966).  Interbedded flows, tuff, and
Jtkm
Talkeetna Formation, Marsh Creek Breccia Member
Massive dark-green to green volcanic breccia having a tuff matrix (Detterman and Hartsock, 1966).  Consists of angular fragments of aphanitic pink and green volcanic rocks ranging in size from 1 cm to nearly 1 m and in general, fine upward.  Interbedded
Jp
Pogibshi formation of Kelley (1980), undivided
Lower Jurassic, Sinemurian to Hettangian and older?
Informally named Pogibshi formation of Kelley (1980) is exposed on east side of Cook Inlet and consists of volcaniclastic rocks interbedded with small amounts of limestone, coal, and tuffaceous argillite.  Kelley (1980) divided the unit into three member
Trpg
Port Graham formation of Kelley (1980)
Upper Triassic; Norian
Dominantly dark-gray, carbonaceous limestone and silty limestone containing varying amounts of silica cement (Kelley, 1980).  Fine-grained, dark-gray siliceous to limy mudstone, silty sandstone, and dark-gray to dark-olive-gray, thin- to medium-bedded ch
JPk
Kakhonak Complex
Jurassic, Triassic, and Permian(?) or older(?)
The Kakhonak Complex, defined by Detterman and Reed (1980) is a lithologically diverse and complex assemblages of metamorphosed mafic plutonic, volcanic, and sedimentary rocks found on the west side of Cook Inlet.  Detterman and Hartsock (1966) mapped "m
Qv
Volcanic rocks, undivided
Andesite, dacite, and basalt lava flows, volcanic breccia, lahar deposits, and debris-flow deposits.  Includes air-fall tuff, volcanic dome deposits, block-and-ash-flow deposits, ash-flow tuffs, volcanic-rubble flows, debris flows, and hot-blast avalanch
Qdf
Debris-flow deposits
Volcanic debris-flow and mudflow deposits from Redoubt Volcano in the Crescent River valley.  Includes several small (older?) deposits in the upper valley and a 3,500-year-old debris flow in the lower valley (F.H. Wilson, unpub. data).  The older deposit
Qad
Andesite and dacite domes
Composite dome complex of Double Glacier Volcano consisting of medium- to coarsely porphyritic hornblende andesite and dacite.  Three K-Ar andesite whole-rock ages were determined on these domes, two are considered minimum ages at 627ñ24 and 763ñ17 ka on
Tvu
Lava flows
middle? to late? Tertiary
A small exposure of dark-blue-gray to black, cryptocrystalline to vesicular basalt and andesite occurs on the mainland northwest of Chisik Island (Detterman and Hartsock, 1966) and is one of a number of scattered exposures in their map area.  As describe
TKgd
Granodiorite
Tertiary and [or] Cretaceous
Medium-grained, hypidiomorphic granular, seriate granodiorite.  Biotite tends to more abundant than hornblende.  Occurs in the northwest corner of the Kenai quadrangle west of the Lake Clark fault and also in the adjacent Lake Clark quadrangle (Reed and
Kqd
Quartz diorite
Cretaceous
Locally foliated, largely medium-grained hornblende-biotite quartz diorite, but includes hornblende-pyroxene gabbro and diorite, quartz diorite, tonalite, and minor granodiorite (Magoon and others, 1976; Nelson and others, 1983; Reed and others, 1992).
KJg
Quartz monzodiorite
Cretaceous and (or) Jurassic
Medium-gray, medium-grained, hypidiomorphic granular hornblende-biotite quartz monzodiorite containing variable amounts of clinopyroxene located in the extreme northwest part of the Kenai quadrangle.  Flow structures locally present and hornblende and pl
Jtr
Alaska-Aleutian Range batholith,Trondhjemite
Late Jurassic
Medium- to coarse-grained, seriate, leucocratic trondhjemite containing 10 percent muscovite and about 5 percent interstitial, perthitic potassium feldspar.  Occurs in two bodies in the Kenai quadrangle immediately west of Redoubt Volcano and in the head
Jg
Alaska-Aleutian Range batholith, Quartz diorite, tonalite, and diorite
Jurassic
Locally foliated medium-grained quartz diorite and tonalite; this is by far the dominant map unit of the Alaska-Aleutian Range batholith in this area.  Hornblende is the primary mafic mineral, biotite increases in proportion to the presence of quartz and
Trdt
Quartz diorite and tonalite
Late Triassic
In the Seldovia quadrangle, this unit includes the diorite of Point Bede and the tonalite of Dogfish Bay of Bradley and others (1999), both on the east side of Cook Inlet.  The diorite of Point Bede of Bradley and others (1999) is fine- to medium-grained
Jsch
Seldovia metamorphic complex
Early Jurassic
Marble, quartzite, garnet-mica schist, and glaucophane-bearing amphibolite whose protoliths were interpreted to consist of limestone, chert, argillite, and greenstone by Bradley and others, (1999).  This unit occurs as narrow fault slices within the Bord
QTy
Yakataga Formation
Quaternary, Pleistocene to Tertiary, Miocene
"Consists of diverse marine and glaciomarine clastic rocks more than 1,670-m-thick on Kayak and Wingham Island and at least an additional 1,200-m-thick on Middleton Island (Plafker and Addicott, 1976).  Much of the continental shelf between Middleton Isl
Tr
Redwood Formation
Tertiary, Pliocene to Oligocene?
Marine mudstone, siltstone, sandstone, and conglomerate (Winkler and Plafker, 1981).  "Lower unnamed sandstone member consists of about two-thirds thick-bedded sandstone and one-third silty sandstone and siltstone.  Upper Puffy Member is more diverse and
Tps
Poul Creek Formation, Sedimentary rocks
Tertiary, early Miocene to late Eocene
"Concretionary, pyritic, glauconitic, reddish-weathering, dark-gray to greenish-gray siltstone, claystone, and sandstone; subordinate dark-brown, laminated shale that is rich in organic material, silty shale, and gray calcareous sandstone; locally includ
Tpv
Poul Creek Formation, Volcanic rocks
"Basaltic pyroclastic and flow rocks, including minor pillowed lava flows; locally interbedded with marine sedimentary rocks, including tuffaceous or glauconitic strata, probably related genetically to mafic dikes, sills, and plugs unit (Tm)" (Winkler an
Tt
Tokun Formation
Tertiary, Eocene
"Consists predominantly of concretionary siltstone and lesser, variable amount of interbedded sandstone, chiefly in lower part of formation.  Thick sandstone beds exposed near Point Hey and on Kayak and Wingham Islands presumably correlate with lower par
Tkt
Kulthieth Formation
"Includes at least 1,500 m of interbedded, massive to thin-bedded, coal bearing arkosic sandstone, dark-gray to black carbonaceous siltstone and shale, and minor coal.  Sandstone to shale ratios in measured sections of the Kulthieth Formation (Martin, 19
Tsw
Stillwater Formation
"Primarily consists of dense hard dark-gray siltstone.  Where siltstone is carbonaceous, it has a coal-like appearance; where it is calcareous, it may be variegated from reddish brown to pale green and usually contains foraminifers" (Winkler and Plafker,
Tos
Orca Group, Sedimentary rocks, undivided
Tertiary, early middle Eocene to late Paleocene
Thin- to thick-bedded graywacke sandstone, siltstone, mudstone, slate, and locally, minor conglomerate, which display abundant sedimentary structures, such as graded bedding, crossbedding, and ripple marks, along with flute, groove, and load casts, indic
Toc
Orca Group, Conglomerate
"Ranges from matrix-supported pebbly mudstone and sandstone to massive clast-supported pebble, cobble, and boulder conglomerate" (Nelson and others, 1985).  Generally well-rounded clasts consist primarily of extrabasinal felsic volcanic and igneous rocks
Kvs
Valdez Group, Metasedimentary rocks, undivided
Upper Cretaceous
Dark-gray, thin- to thick-bedded, laumontite to mid-greenschist facies metamorphosed, moderately to poorly sorted sandstone, siltstone, and mudstone flysch; sandstone is fine- to coarse-grained and mainly composed of plagioclase, quartz, and igneous rock
Kvvs
Valdez Group, Interbedded metavolcanic and metasedimentary rocks
Approximately equal portions of interbedded metavolcanic and metasedimentary rocks (Winkler and Plafker, 1981; Nelson and others, 1985; Winkler and Plafker, 1993).  Metavolcanic rocks include semischistose volcanic breccia, tuff, tuffaceous sediment, and
Kvv
Valdez Group, Metavolcanic rocks, undivided
Tholeiitic metabasalt, massive greenstone, and basaltic metatuff, including local pillow lava, pillow breccia, and gabbroic dikes and sills (Winkler and Plafker, 1993) in the Cordova quadrangle.  Metabasalt forms rugged, nearly massive outcrops, whereas
Kvt
Valdez Group, Aquagene tuff
Metamorphosed aquagene tuff is green to dark-gray, fine-grained, and finely laminated containing plagioclase phenocrysts; metamorphosed to chlorite and biotite zones of greenschist facies; chlorite, epidote, and locally, actinolite are abundant; remnants
Kvgs
Valdez Group, Schist
In the Valdez Group, schistose metamorphic rocks are found in two general modes of occurrence.  In the Cordova quadrangle, Winkler and Plafker (1993) describe a "chiefly homogenous pelitic schist and minor amphibolite; [unit which] also includes spotted
Kvgg
Valdez Group, Gniess
"Muscovite-biotite-quartz-plagioclase (ñ sillimanite and garnet) schist, banded gneiss, and migmatitic gneiss; potassium-feldspar-bearing segregations in migmatite; many local intrusive stringers, dikes, and sills of granodiorite and granite; transitiona
Kvm
Valdez Group, Mlange of Iceworm Peak of Kusky and others (1997)
Tectonic mlange consisting of blocks of graywacke in a phacoidally cleaved matrix of slate having a Valdez Group protolith for both matrix and blocks (Bradley and others, 1999; Bradley and Wilson, 2000).  Mapped only in the Seldovia and Kenai quadrangle
KMm
McHugh Complex
Cretaceous to Mississippian
"Mlange of siltstone, sandstone, mud-chip sandstone, conglomeratic sandstone, tuff, and less abundant gabbro, serpentinite, bedded chert, and pillow basalt; fine-grained sedimentary strata commonly streaked out; sedimentary and igneous rocks are broken
KJms
McHugh Complex, graywacke and conglomerate
Early Cretaceous to Early Jurassic, Pliensbachian
Consists of fault-bounded blocks of massive conglomerate and graywacke that range up to several kilometers in structural thickness (Bradley and others, 1999).  Bradley and others (1999) reported that deformation has generally obliterated primary sediment
KTrmc
McHugh Complex, basalt and chert
Early Cretaceous, Albian to Middle Triassic, Ladinian
"Pillow and massive basalt, depositionally overlain by complexly folded and faulted radiolarian chert" (Bradley and others, 1999).  Bradley and others (1999, citing a C.D. Blome, USGS written commun. of 1994) reported radiolaria in bedded chert ranging i
Mzg
McHugh Complex, Gabbro
Mesozoic
Dark-green, medium- to coarse-grained gabbro and minor leucogabbro and plagiogranite (Bradley and others, 1999).  Occurs as fault-bounded bodies in the McHugh Complex; following Bradley and others (1999), only the larger bodies are shown here; others are
Mzu
McHugh Complex, Ultramafic plutonic rocks
Predominantly layered, variably serpentinized dunite containing rare to locally abundant layers of chromite and pyroxenite and fault slices of garnet pyroxenite and serpentinite (Bradley and others, 1999).  Bradley and others (1999) reported at least 7 f
Tdc
Dacite of Cape Saint Elias
Tertiary, Pliocene or Miocene
Described by Winkler and Plafker (1993) as follows:  "Prominent very pale gray dacite plug complex that forms Cape Saint Elias and Pinnacle Rock at the southwestern end of Kayak Island (Plafker, 1974).  Dacite is very dense and hard and is conspicuously
Tm
Mafic plugs
Tertiary, Oligocene?
Strongly altered dikes, sills, and plugs of diabase, alkalic basalt, olivine basalt, and lamprophyre, mostly on or near Kayak Island.  Winkler and Plafker (1993) suggested these hypabyssal rocks were probably genetically related to extrusive volcanic roc
Tg
Granitic rocks
Tertiary, Oligocene? and latest Eocene
Plutons in the Seward quadrangle are dominantly light-gray, medium- to coarse-grained biotite ñhornblende granodiorite and granite stocks; larger stocks commonly grade inward from marginal zones containing more biotite (and locally hornblende) to more le
Tgd
Gabbro and diorite
Tertiary, Oligocene and older
Dominantly, dark-gray medium- to coarse-grained gabbro and subordinate diorite, both having finer grained borders of quartz gabbro and quartz diorite (Tysdal and Case, 1979; Nelson and others, 1985).  Gabbro generally composed of subequal amounts of labr
Tgg
Granite and granodiorite
Generally medium- and medium- to coarse-grained hypidiomorphic-granular biotite granite having border phases of biotite-hornblende granite, granodiorite, and tonalite (Nelson and others, 1985) located in the Cordova quadrangle.  Also includes uncommon da
Tgh
Granitic rocks of Harding Icefield region
Primarily "medium- to dark-gray foliated medium- to coarse-grained biotite-muscovite-(hornblende) granite and granodiorite; marginal phases are locally biotite-muscovite-(hornblende) tonalite" (Tysdal and Case, 1979).  Consists of a large batholith exten
Tov
Ophiolitic rocks of Prince William Sound, Volcanic rocks, undivided
"Thick and thin tabular bodies of altered tholeiitic basalt consist of pillowed, massive, or crudely columnar flows, but also include pillow breccia, aquagene tuff, and diabase or gabbro sills; pillows have chilled margins that are palagonitic and amygda
Ophiolitic rocks of Prince William Sound, Pillow basalt
"Pale- to dark-green aphyric to porphyritic, frequently amygdaloidal, pillow basalt composed of plagioclase and clinopyroxene; plagioclase commonly replaced by albite and epidote, and clinopyroxene by hornblende, actinolite, and(or) chlorite; vesicles mo
Tovs
Ophiolitic rocks of Prince William Sound, Volcanic and sedimentary rocks
Consists of locally variable amounts of tholeiitic basalt, and tuffaceous and generally minor turbiditic sedimentary rocks (Winkler and Plafker, 1993; Nelson and others, 1985; Tysdal and others, 1976).  The lithology is quite variable throughout the stud
Tod
Ophiolitic rocks of Prince William Sound, Sheeted basalt dikes
Mafic sheeted-dike complexes consisting of dark-green, gray, and brown, aphanitic to porphyritic; chiefly basaltic, but locally gabbroic to dioritic, dikes (Tysdal and others, 1977; Tysdal and Case, 1979).  In the Knight Island area, felsic plagioclase-q
Togb
Ophiolitic rocks of Prince William Sound, Gabbro
"Medium- and dark-gray to green coarse-grained chiefly clinopyroxene-plagioclase rocks with ophitic to subophitic texture and gabbroic to dioritic composition; locally pegmatitic with clinopyroxene crystals as much as 5 cm long; clinopyroxene commonly is
Tou
Ophiolitic rocks of Prince William Sound, Ultramafic rocks
"Dunite, locally with layers of chromite, moderately to mostly altered to serpentine, serpentine-talc, and talc schist; lustrous pale- to dark-green and black, locally reddish weathering rock that forms dike-like and irregularly shaped intrusive bodies"
Tmu
Mafic and ultramafic plutonic rocks
Tertiary, Eocene and Paleocene?
"Compositionally and texturally variable unit consists mainly of clinopyroxene gabbro, two-pyroxene gabbro, and local diabase, hornblende gabbro, peridotite, and orthopyroxenite.  Gabbro commonly is medium-grained and equigranular and is slightly to mode
TKd
Dikes
early Tertiary to Early Cretaceous
Dikes of dacite, rhyolite, andesite, and rare basalt intrude rocks of the Valdez Group (Kvs) and McHugh Complex (KMm) (Bradley and others, 1999).  Analyzed samples of dikes yield a wide range of ages, as shown in Table 1.  A basaltic-andesite dike intrud
bu
Bedrock unknown
Unit does not appear on published map
Tuxedni Group, Red Glacier Formation
Middle Jurassic, lower Bajocian to lower middle Bajocian
Thin-bedded to massive, red-brown weathering, dark-gray to moderate olive-gray, highly arenaceous siltstone, locally containing lenticular interbeds and concretions of reddish-gray, dense limestone and very minor coal seams (Detterman and Hartsock, 1966)