Q
Undifferentiated surficial deposits
Quaternary
The deposits include alluvium, colluvium, talus, landslides, rock glaciers, eolian and paludal deposits, and a variety of lacustrine, morainal, and ice contact.
VA002
Valdez
Unconsolidated
Qs
Surficial deposits
Holocene and Pleistocene
Surficial deposits, undifferentiated
GU002
Gulkana
Holocene
Surficial deposits, undifferentiated -- Alluvium deposited by nonglacial streams and outwash deposited by glacial meltwater.
CV003
Cordova
Qu
Surficial deposits, undivided
Predominantly alluvium deposited by nonglacial streams and outwash deposited by glacial meltwater.  Consists of sand and gravel; terminal, lateral, and ground moraine composed of unsorted deposits of boulders, cobbles, gravel, and sand left by the retrea
CV002
BG003
Bering Glacier
VA003
Undifferentiated slope deposits, including glacial and alluvial deposits.
MC004
McCarthy
Alluvium, older alluvium, colluvium, talus, landslides, rock glaciers, glaciolacustrine deposits, glacial outwash deposits, and a variety of moraines
MC002
yellow
Recent glacio-fluvial deposits
Quaternary, Holocene
glacio-fluvial deposits
CV005
Glacio-fluvial deposits
CV006
Qa
Alluvial deposits
Alluvium of active flood plains and lowest terraces of major streams, and larger alluvial fans.  Boulders, gravel, and sand
NB002
Nabesna
Qau
Alluvium, undivided
Alluvium
Primarily well-sorted stratified gravel and sand deposited by nonglacial streams and outwash deposited by glacial meltwater.  Locally includes lake and terrace deposits
BG002
Qal
Alluvium along streams and in fans
Mainly in active flood plains and lowermost terraces of major and some minor streams and in larger active fans.  Stratified silt, sand, gravel, and boulders.
MC003
Active alluvium
Active alluvium in larger streams and fans
Alluvium along streams
Mainly in active flood plains of major and some minor streams.  Chiefly stratified boulders, cobbles, gravel, and sand; silt locally common.
NB008
Younger alluvium
Alluvium on active flood plains and on lowest terraces of major streams.  Chiefly boulders, gravel, and sand.
NB004
Alluvium in streams
Includes alluvium in active flood plains and in principal terraces of major and some minor streams.  Chiefly stratified silt, sand, gravel, and boulders.
VA007
Young alluvial deposits - Alluvium
Alluvium underlying active flood plains and low terraces of major and some minor streams.  Chiefly pebble to cobble gravel, and sand.  Some small deposits are finer grained and include silt, sand, and gravel
GU101
Alluvium, Modern coarse-grained stream alluvium
Active flood plains and lower terraces of larger streams.  Chiefly gravel and sand, some boulders; generally stratified
NB108
Qalf
Alluvium, Modern fine-grained stream alluvium
Restricted to active flood plains.  Chiefly sand and silt, some gravel; generally stratified
Unconsolidated detritus, chiefly silt, sand, and gravel, that generally is poorly sorted and locally is imbricated
MC100
Alluvial and outwash deposits
Mainly fluvial and fluvio-glacial gravel, sand, and mud. Includes smaller areas of talus, glacial, and lacustrine sediments
YA002
Yakutat
MS002
Mount Saint Elias
Chiefly well-sorted gravel and sand, minor silt, and boulders in higher terraces along larger streams and active alluvial fans
IB003
Icy Bay
BG004
Alluvium in active streambed and lowest terraces along larger streams and in active alluvial fans. Chiefly well-sorted gravel and  sand, minor silt and boulders
YA003
GU003
Alluvium in active streambed and lowest terraces along larger streams and in active alluvial fans. Chiefly well-sorted gravel and sand, minor silt and boulders
GU004
Alluvium underlying active flood plains and terraces of major streams.  Chiefly gravel and sand
NB109
NB007
Qaf
Alluvium in fans
Mainly large active fans and cones on steep to gentle slopes.  Chiefly poorly stratified boulders, cobbles, gravel, and sand.
Alluvial fans and cones.  Chiefly boulders, gravel, and sand.  Only larger, better defined cones differentiated from unit Qcu.
Mainly large, broad, generally active fans and cones on mountain slopes chiefly along major streams.  Chiefly sand, gravel, and boulders.
Young alluvial deposits - Alluvium in fans
Alluvium in fans deposited by active, steep-gradient streams.  Mostly pebble and cobble gravel, and sand; locally silt and boulder gravel.  Includes some glacial outwash from young phase of Alaskan Glaciation
Qoaf
Old alluvial deposits - Alluvium in fans
Alluvium in fans and cones that are not graded to present-day stream levels.  Chiefly cobble to pebble gravel, and sand; locally silt, boulder gravel, and organic deposits.  Commonly overlain by veneer of younger alluvial and colluvial deposits.  Include
Alluvium, Coarse-grained alluvial fans and cones
Chiefly gravel and sand that hve been actively water transported.
Qaff
Alluvium, Fine-grained alluvial fans and cones
Usually margins of larger fans; chiefly sand and silt
Alluvial fans
Alluvial fans and cones; only larger, better defined cones differentiated from Qcu.  Chiefly gravel and sand
Qc
Colluvial deposits
Colluvium, undivided
Qco
Colluvial deposits, river bluff type
Qsw
Slope-wash deposits
Quaternary (Holocene)
Slope wash deposits in northeast part of map.  Thought to include: Boulder- to pebble-size, angular rock debris derived from mass wasting of bedrock and overlying moraine deposits along walls of the larger valleys.  Includes undifferentiated small landsl
Qt
Talus deposits
Talus
Talus-- Boulder- to pebble-sized, angular rock debris.
Qca
Colluvium, undifferentiated
Talus, but also includes deposits of small landslides, rock glaciers, and other products of mass-wasting processes, and alluvium in small fans and cones.  Poorly sorted silt, sand, gravel, and boulders
Qcb
Bluff colluvium
Basin bluff colluvium
Chiefly talus but also includes deposits of small landslides, rock glaciers, and other mass-wasting processes.  Chiefly unsorted boulders, cobbles, gravel, and sand.
Qcu
Undifferentiated colluvium on valley walls and hill slopes.  Chiefly rubble, gravel, sand, silt, and diamicton;  typically poorly sorted.
Chiefly talus but includes deposits of small landslides, rock glaciers, and other mass-wasting processes.  Generally includes a large proportion of alluvium in small fans and cones and reworked glacial deposits.  Cheifly poorly sorted silt, sand, gravel,
Colluvial deposits - Colluvium and alluvium mixed
Predominantly colluvium but includes a large percentage of alluvium from small streams.  Mostly diamicton, gravel, and sand
Colluvial deposits - River bluffs
Colluvium on river bluffs developed in unconsolidated deposits.  Mostly diamicton, sand, gravel, and silt
Colluvial deposits - Undivided
Undivided mass-wastage deposits on moderately steep slopes underlain by bedrock or surficial deposits.  Chiefly diamicton, silty gravel, silty rubble, and sand.  Most deposits originate by downslope movements such as creep, solifluction, and various type
Qcvg
Colluvial deposits - Includes volcanic debris flows
Quaternary, Holocene and Pleistocene
Colluvium underlying gently to moderately steep slopes mostly on northwestern and northern flanks of Mount Drum above about 1200 m.  Includes volcanic debris flows and rocks derived from more easily weathered bedrock locally mixed with glacial deposits o
Colluvial, undifferentiated
Chiefly talus and slope debris that has not been actively water transported.  Includes various minor unconsolidated features.  Poorly sorted, silt to boulders
Widespread elongate lobes and coalescing aprons.  Mainly angular rock fragments
Larger areas of poorly sorted, angular deposits forming cones and aprons at the base of steep slopes
Slope deposits, undifferentiated
Sand, gravel, boulders, diamicton, and rubble colluvium (talus and small landslides), but may also include small glacial, rock glacier, and alluvial deposits
tan
Colluvium along the high steep bluffs of the Copper River and its principal tributaries.  Includes numerous local exposures of Copper River deposits (unit Qcr) and drift of older glaciations (unit Qg).  Unsorted silt, sand, gravel, and boulders
Colluvium undifferentiated
Undifferentiated colluvium on valley walls and hill slopes.  Chiefly talus and other slope debris but includes alluvium of numerous minor streams and locally, glacial, rock glacier, and other mass-wasting deposits.  Chiefly rubble, gravel, sand, and silt
Ql
Landslide deposits
Qls
Larger deposits of unsorted, angular rock debris derived by massive failure of steep bedrock slopes.
Landslides
Landslides-- Unsorted, angular rock debris derived by failure of bedrock slopes.
Includes large slump and debris avalanche deposits.  Particularly common along steep north flank of mountain escarpment south of Beaver Creek.  Slump deposits consist chiefly of masses of volcanic rock as much as hundreds of meters wide; deposits are chi
Larger landslides; arrows show downslope movement direction.
Mount St. Elias
Qcl
Colluvial deposits.  Young landslide deposits.  Chiefly debris avalanches.
Landslide deposits of all types, including slumps, block glides, earthslides, debris slides and flows, debris avalanches, and rockfalls; includes massive slump deposits within volcanic avalanche deposits (Qva) in Nadina River and nearby valleys.  May inc
Colluvial, landslide deposits
Yound fresh debris avalanches.  Chiefly coarse rubbly diamicton
Includes slumps, earth-debris flows, block glides, and debris avalanches.  Diamicton and rubble
Conglomerate
Pleistocene
Conglomerate, fluvial deposits derived from Wrangell Lava and deposited on unit QTu, undifferentiated volcanic rocks and older, pre-Wrangell rocks
Sedimentary
Qao
Older alluvium
Older alluvium in larger streams and fans
Qoa
Deposits in higher terraces along major streams and in old dissected alluvial fans.  Chiefly boulders, gravel, and sand.
Chiefly sand, gravel, and boulders; may include some diamicton. Maximum thickness about 150m.
Old alluvial deposits
Alluvium underlying intermediate and high terraces near major streams.  Chiefly pebble to cobble gravel, and sand.  Includes glacial outwash from various phases of Alaskan Glaciation.  Four sequences of deposition recognized on outwash flood plains below
Mapped on higher terraces along larger streams; probably related to the older phase of the Alaskan Glaciation.  Chiefly gravel and sand
Benches and terraces that support vegetation along ancestral flood plains.  Unconsolidated detritus, chiefly silt, sand, and gravel, that generally is poorly sorted and locally is imbricated
Chiefly well-sorted gravel and sand, also minor silt, and boulders in higher terraces along larger streams and inactive alluvial fans.  Predominantly of Pleistocene age, may include localized Holocene deposits
Alluvium in higher terraces along larger streams and in inactive alluvial fans.  Chiefly well-sorted gravel and sand, minor silt and boulders.  Predominantly of Pleistocene age, localized deposits include the Holocene
Qfl
Fluviolacustrine deposits
Deposits of lakes, ponds, and low-gradient streams.  Sand, silt, and clay
Qgl
Glaciolacustrine deposits
Deposits of glacial lakes.  Clay, silt, sand, and minor gravel
Fluviolacustrine and swamp deposits
Mud, clay and peat
Fine-grained deposits
Chiefly silt, clay, fine sand, peat, and other organic material in ponds, swamps, lagoons, and along low-gradient streams
lt green
Recent Lacustrine deposits
Lacustrine deposits
In ponds, swamps, lagoons, and along low-gradient streams.  Chiefly silt, clay, fine sand, peat and other organic material
Qb
Beaches and spits
Constructional shoreline deposits of well-sorted gravel and sand formed as spits extending westward or northwestward from headlands and beaches consisting of successive sequences of marshes and ridges extending landward from the present shoreline.
Beaches, spits, and offshore bars
Beaches, spits, and offshore bars -- Constructional shoreline deposits of well-sorted gravel and sand.
Beach
Wave deposited sand and gravel.
Marine shoreline deposits
Mainly sand and gravel of present and former beaches, beach ridges, beach bars and spits.  Includes smaller sand dunes
IB002
Lagoonal deposits
Intertidal mud and sand deposited in swamp areas between beach ridges and in tidal embayments, single polygon at toe of Malaspina Glacier
Lagoonal deposits--Fine-grained silt rich in organic material, mud, and peat.
Intertidal mud and sand deposited in swamp areas between beach ridges and in tidal embayments
Qms
Mineral spring and mud volcano deposits
Qme
Mineral spring deposits
Chiefly mud
Qsm
Upper Klawasi Mud Volcano cone.  Chiefly silt and clay deposited by mud-rich, relatively warm Na-Cl-HCO3 springs; includes some glacial drift deposits
Chiefly mud (clayey silt) deposited by warm, Na-HCO3-rich saline water charged with CO2 from 3 active springs (Klawasi mud volcanoes) west of Mt. Drum and at least one inactive spring west of Capital Mountain.  Unit also includes the Copper Center spring
Qe
Eolian deposits
Dune, and remnant sand dune, deposits.  Sand and silt
Qds
Active cliff-head dune deposits
Qd
Dunes
Well-sorted fine-to medium-grain sand with abundant driftwood and sparse pebbles along the coast south of Bering Glacier.  Dunes are nourished by prevailing southeasterly storm winds that blow across outwash deposits of the Bering Glacier.
Dunes-- Well sorted, fine grained sand and silt aligned in longitudinal ridges.
Eolian/Dune
Sand dunes
Larger sand dunes associated with present beaches and streams
Deltaic deposits
Associated with higher lake levels during the Alaskan Glaciation.  Sand and gravel
Late Pleistocene
Glaciolacustrine deposit
Interbedded lake and glacial deposits of the Copper River basin
Drift of Wisconsin Glaciation - Glaciolacustrine
Quaternary, Pleistocene
Glaciolacustrine deposits on floor and sloping shore areas of glacial Lake Atna.  Mostly clayey silt and silty fine sand; locally pebbly silt.  Sand and pebble gravel near shorelines, especially close to 745 m elevation
Pond and lake sediments - Deposits associated with high lake levels during the Alaskan Glaciation.  Others from small ponds and commonly covered with peat.  Chiefly clay and silt
Qgf
Glaciofluvial deposits
The glaciofluvial deposits, broadly distributed below 900 m in elevation, are, in part, products of intermittent deposition in a large periglacial Pleistocene lake that occupied extensive parts of the Chitina Valley and Copper River Basin.  Also included
Qcr
Copper River deposits, undifferentiated
Interbedded glaciolacustrine, glacial, and alluvial deposits including those of glacial Lake Atna at the surface.  Chiefly clayey to pebbly silt and diamicton, with many local to regional beds of gravel and sand.  Locally overlain by fine-grained alluviu
Qlg
Deposits of the Copper River Basin, undifferentiated
Chiefly diamicton interbedded with stratified lacustrine sediments.  The diamicton interbedded in the lake sediments ranges from non-sorted till to deposits of poorly sorted material that exhibits graded bedding. The lake sediments, consisting of sand, s
Qm
Moraines
Lateral, end, and a few ground moraines that are relics of extensive glaciation.  They consist of jumbled boulders with broad ranges in size and composition.  Older moraines are weathered and support vegetation
lime
Older glacial deposits
Glacial deposits
Supraglacial moraine
Unweathered, poorly sorted, pebble- to boulder sized rock debris on surfaces of alpine and valley glaciers.
Supraglacial moraine-- Unweathered, poorly sorted, debris on surfaces of glaciers.
Supraglacial deposits
Unsorted angular debris ranging in size from silt to blocks on surfaces of the present glaciers.
Qaga
Drift of Alaskan Glaciation - Ablation moraines
Chiefly ablation moraine on existing glaciers.  Largely rubble and diamicton underlain by glacier ice
Qmi
Moraines on ice
Moraines on ice that mantle active glaciers.  Dominantly fresh boulders and form veneers
Stipple
Superglacial drift
Rock debris on existing glaciers
Qsg
Superglacial Drift
Qr
Rock glacier deposits
Tallis and deposits from recently active, and recently active, rock glaciers.  Rubble and diamicton
Qrg
Rock glaciers
Unweathered, poorly sorted, pebble- to boulder sized rock debris and ice
Deposits of active rock glaciers exhibiting well-defined lobate form.  Chiefly angular blocks and diamicton
Rock glacier deposit
Deposits in bith active rock glaciers and inactive rock glaciers.  Chiefly angular blocks and diamicton.
Active and recently active rock glaciers.  Chiefly rubble and diamiction.
Chiefly angular blocks and diamicton.
Includes deposits that are active or were recently active in generally well defined lobate forms, and deposits of old, generally inactive, rock glaciers with less well defined and commonly smooth margins.  Chiefly rubble and diamicton
Diamicton of active rock glaciers
Hummocky lobate masses consisting of disarrayed angular and blocky boulders and smaller rocks that are partly cemented by ice
Chiefly blocks of rubble lying on buried glaciers exhibiting well-defined lobate forms.  May or may not include glacier cores at depth
Rock Glacier deposits
Includes deposits of active, recently active, and formerly active rock glaciers.  Chiefly rubble and diamicton
Solifluction deposits
Deposits on low-angle, low-relief slopes at relatively high elevations.  Mostly bedrock rubble but may include some Wisconsin and older glacial drift
Solifluction and older glacial deposits
Deposits on low-angle, low-relief slopes, at high elevation.  Mostly bedrock rubble, but includes some glacial drift.  Some of Qs was probably covered by Wisconsin ice, whereas all of Qs was covered by pre-Wisconsin ice
Chiefly colluvium (talus and small landslides) but may include local glacial, rock glacier, and alluvial deposits.  Sand, gravel, boulders, diamicton, and rubble
Colluvial - Solifluction
Solifluction and creep surfaces on high-level low-gradient slopes.  Chiefly bedrock rubble but may include older glacial drift deposits
Qwfe
Drift of Wisconsin Glaciation - Eskers
Prominent eskers.  Chiefly gravel and some sand
Qag
Drift of Alaskan Glaciation.  End and lateral moraine deposits of receding glaciers.  Rubble and diamicton
Younger glacial moraine
Undifferentiated terminal, lateral, and ground moraine.  Locally includes and kame and esker deposits of Guyot Glacier around Icy Bay.
Terminal, lateral, and ground moraine
Terminal, lateral and ground moraine-- Unsorted boulders, cobbles, gravel and sand deposited during retreat of glaciers.
Alaskan glaciation deposits
Terminal and lateral moraine at base of small ice field.  Chiefly diamicton
Drift of Alaska glaciation
Younger end, ground, and lateral moraine deposits
Mainly till, but locally includes lacustrine and glaciofluvial deposits.  Arrow indicates direction of ice movement as inferred from trend of elongate trenches and ridges.  Advance of Hubbard Glacier culminated in Yakutat Bay between 1700 and 1791 A.D.
Drift of Alaskan glaciation
End, lateral, and ground moraine of the Alaskan glaciations which were deposited during the recession of existing glaciers.  Diamicton and rubble; local gravel and sand.
Qam
Drift of the Alaskan Glaciation
Drift of the Alaskan Glaciation
Chiefly rubble and diamicton.
Includes end and lateral moraines of the younger and older phases of Alaska glaciation, deposited after recession of existing glaciers.  Diamiction, local gravel, and sand.
Drift of Alaskan Glaciation - Younger phase
Mostly end and lateral moraines, including some ground moraine, generally in front of existing glaciers.  Rubble, diamicton, and some gravel and sand.  May include some rock glaciers and drift of the old phase of Alaskan Glaciation
Qoag
Drift of Alaskan Glaciation - Older phase
Mostly end and lateral moraines, locally in front of rock glaciers.  Chiefly diamicton and rubble; some gravel and sand.  Covered in places by colluvial deposits
Glacial deposits of the Alaskan Glaciation
Ablation and termianl moraines directly related to existing glaciers; may include some older deposits.  Mostly rubbly till
Qmo
Older end, ground, and lateral moraine deposits
Glaciomarine till and till associated with a neoglacial advance of the Hubbard Glacier system which culminated in Yakutat Bay between 970 and 1290 A.D.
Older glacial moraine
Undifferentiated terminal, lateral, and ground moraine of Guyot Glacier around Icy Bay.
Drift of Alaskan (Neoglacial) glaciation
Diamicton, local gravel, and sand in end, lateral, and ground moraines, kames, and outwash proximal to present glaciers; includes small rock glaciers
Glacial deposits, undivided
Younger glacial deposits, undivided
glacial deposits
End, lateral, and ground moraine and kames and outwash proximal to present glaciers.  Includes rock glaciers too small to map.  Diamicton, local gravel and sand
Drift of Alaskan Glaciation
Chiefly end and lateral moraines of the stade of the Alaskan Glaciation.  Diamicton and rubble; local gravel
Drift of Alaskan (neoglacial) glaciation
Quaternary, Holocene (neoglacial)
Qoal
Mainly outwash related to Alaskan glaciation and possibly younger phase of Wisconsin glaciation.  Stratified silt, sand, gravel, and boulders.
Qwg
Drift of Wisconsin glaciation.  End, lateral, and ground moraine and fluvialglacial deposits.
Qwl
Younger Wisconsin glaciation deposits
Terminal and lateral moraines of late(?) phase of Wisconsin glaciation.  Chiefly diamicton and rubble
Qog
Older glaciation deposits
Drift of older glaciations.  Includes lake deposits in the Chitina River valley.
Drift of Wisconsin glaciation
Drift of Wisconsin glaciation.  Chiefly lateral and ground moraine of both younger and older stages of Wisconsin glaciation.  Diamicton and rubble; local gravel and sand.
Drift of older glaciations
Drift of Wisconsin glaciation.  Chiefly diamicton; local sand, gravel and boulders.
Qlo
Drift of Late Wisconsin age
Drift of Late Wisconsin age
Well-defined outwash fan.  Chiefly gravel and sand.
Qld
Drift of Late Wisconsin age
Ground moraine, chiefly diamiction.  Includes minor fluvioglacial deposits of gravel and sand and scattered pond and fine-grained alluvial deposits of sand, silt, and clay.
Qmd
Drift of Main Wisconsin age
Drift of Main Wisconsin age
Ground moraine, chiefly diamicton.
Drift of Older Glaciations
Drift of Older Glaciations
Chiefly diamicton and boulder deposits.
Qyg
Drift of younger (Wisconsin) glaciation
Well defined lateral moraines high on the valley walls of the Dadina, Chetaslina, and East Fork of the Chetaslina Rivers.  Diamicton.
Qwmc
Drift of Wisconsin Glaciation - Channeled ground moraine
Area of drift deposits, mainly ground moraine, extensively channeled and eroded by glacier melt-water streams.  Channels contain some gravel and sand, overlain in many places by silty organic deposits
Qwm
Drift of Wisconsin Glaciation - Ground moraine
Drift, mostly gently rolling to undulating ground moraine exhibiting some linear and few drumlinoidal ridges.  Includes outwash in channels cut into drift by glacier melt-water streams and some ice-contact deposits, lateral moraines, and colluvial deposi
Qwml
Drift of Wisconsin Glaciation - Lateral moraines
Mostly lateral moraines perched along valley walls.  Chiefly diamicton and rubble.
Qwme
Drift of Wisconsin Glaciation - End moraines
Principally complexes of end with some lateral moraines; includes some ground-moraine and ice-contact deposits.  Chiefly diamicton, with some gravel, sand, and silty organic deposits
Qlm
Glacial deposits of the late Wisconsin
Old terminal, lateral, and ground moraines.  Chiefly till
Qmm
Glacial deposits of the main Wisconsin Glaciation
Chiefly ground and lateral moraines.  Includes drumlinoid features.  Chiefly till
Qg
Chiefly diamicton, local gravel, and sand in end, lateral, and ground moraines of Wisconsin and older glaciations.  Locally includes kames, kame-like deposits and outwash.  Also includes glaciolacustrine deposits (Qcr) near the complex interface with Gla
Chiefly diamicton, local gravel, and sand in end, lateral, and ground moreanie of Wisconsin and older glaciations.  Locally includes kames, kame-like deposits, and outwash.
End, lateral, and ground moraine of Wisconsin and older glaciations.  Locally includes kame and kame-like deposits and outwash.  The Chitina River valley includes glaciolacustrine deposits near the complex interface with glacial Lake Atna.  Chiefly diami
Drift of Wisconsin Age - Moraines
Well-defined lateral moraines of the late Wisconsin age.  Chiefly diamicton
Drift of Wisconsin Age - Undifferentiated
Undifferentiated glacial, fluvioglacial, and volcanoglacial deposits.  Probably represent more than one episode of Wisconsin Glaciation.  Chiefly diamicton and sand and gravel
Older Wisconsin glaciation deposits
Ground moraine of main(?) phase of Wisconisin glaciation.  Diamicton, local gravel and sand
Qwo
Fluvio-glacial deposits
Outwash related to main(?) phase of Wisconsin glaciation.  Silt, sand, gravel, and boulders
Drift of Wisconsin Glaciation - Outwash
Outwash probably of main phase of glaciation.  Located in well-defined plains and broad channels; surface pitted in places.  Chiefly well bedded gravel and sand, mantled locally by organic silt
Qwf
Drift of Wisconsin Glaciation - Fluvioglacial
Fluvioglacial ice-contact deposits mainly in kames and small eskers.  Includes some small outwash and ground-moraine deposits.  Typically silt-laden pebble and some cobble gravel; locally short beds of sand and silt
Glacial drift deposits older than Wisconsin glaciation; probably of Illinoian age
Drift of older (Wisconsin and older?) glaciation
Chiefly ground moraine extensively modified by alluvial and colluvial processes.  Diamiction; locally alluvial sand, gravel, and boulders.
Qig
Drift of intermediate glaciation
Drift deposits mostly on moderately steep slopes.  Chiefly ground with some lateral moraines; a few ponds.  Mostly diamicton and some gravel.  Locally mixed with and overlain by colluvial and alluvial deposits
Qigl
Drift of intermediate glaciation - lateral moraines
Lateral moraines, some of which have gently sloping ridge crests.  Chiefly diamicton and rubble
Undifferentiated glacial and fluvioglacial deposits interlayered with occasional thin volcanic flows.  Observed only in north wall of Jacksina Glacier valley where unit is overlain by a dacitic andesite agglutinate flow (Qdaa) approximately 1.3 my old.
Drift of older glaciation
Chiefly ground-moraine and fluvial (?) deposits on a few gently sloping plateaus and ridge crests about about 1500 m elevation on northern parts of Mt. Drum.  Diamicton and accumulations of subrounded to rounded pebbles, cobbles and boulders.  Pre-Wiscon
Tg
Glacial, fluvioglacial, and boulder deposits
Tertiary
Weakly consolidated, poorly sorted, fluvioglacial deposits, glacial volcanic boulder deposits, and localized tillite
Lignitized wood
Qcg
Weakly indurated pebble to boulder conglomerate and interbedded lenses of sandstone.  Conglomerate is continuation of more extensive sedimentary rock unit mapped in the contiguous Gulkana A-1 quadrangle (Richter and others, 1994).
Qw
Wrangell Lava (younger part)
Andesite and dacite flows, dacite domes, and interbedded breccias and pyroclastic rocks (near Mount Shields stratovolcanoes). basalt, andesite, and dacite flows and basaltic lapilli tuff (near Icefields Plateau area), dacite flow (near Drop Glacier and C
Igneous
Qcc
Volcanic rocks-Capital Volcano
Caldera lavas
Qcs
Shield lavas
Qdf
Volcanic rocks-Drum Volcano
Cone building flows
Qsf
Volcanic rocks-Sanford Volcano
Basalt, andesite, and dacite lava, undifferentiated
Volcanic rocks-Wrangell Volcano
Holocene (?) and Pleistocene
Andesite flows and fragmental rocks
Qwc
Wrangell Volcano -- East Crater deposits
Wrangell Volcano -- East Crater deposits.  Altered flows, breccias, and tuffs.
Qwa
Wrangell Volcano -- Two-pyroxene high-silica andesite flows
Wrangell Volcano, two-pyroxene high-silica andesite flows.
Medium- to dark-gray, thin to thick (5-30 m) lava flows that generally exhibit oxidized and slightly scoriaceous tops and bottoms.
Qwbf
Wrangell Volcano -- Olivine basalt flow and breccia
Wrangell Volcano, olivine basalt flow and breccia.
Qwbc
Wrangell Volcano -- Cinder cone
Wrangell Volcano, cinder cone.  All rocks probably of basalt or basaltic andesite composition.
Qsd
Mount Sanford volcano -- Low-silica dacite flows
Mount Sanford volcano, low-silica dacite flows
Qsy
Mount Sanford volcano -- Young basaltic andesite, andesite, and dacite lavas, undifferentiated
Mount Sanford volcano, young basaltic andesite, andesite, and dacite lavas, undifferentiated
Qso
Mount Sanford volcano -- Older volcanic rocks
Mount Sanford volcano, older volcanic rocks.  Chiefly interlayered thick lava flows, flow breccias, and debris and mudflow deposits that are mostly of andesitic or basaltic andesitic composition.
Qbf
Flows
Flows are equivalent to the olivine andesite flows (unit Qf) mapped in the contiguous Nabesna B-6 quadrangle (Richter and others, 1993).
Qaa
Andesite agglutinate
Andesite agglutinate, local source probably derived from the collapse of a large cinder/spatter cone in the area now covered by a younger dacitic center in the adjacent Nabesna A-5 quadrangle.
Qdv
Andesite flows
Mt. Drum volcano.  Medium to dark gray, porphyritic olivine-bearing andesite lava flows containing phenocrysts of plagioclase, olivine, and orthopyroxene in a cryptocrystalline groundmass.
Mt. Wrangell west summit crater
Altered flows, breccias, and tuffs.
ALT
Mt. Wrangell shield lava
Mt. Wrangell shield lava.  Medium to dark gray, moderately to highly porphyritic two-pyroxene high-silica andesite flows.
Whole rock K/Ar ages range from 282 ka to 516 ka
Qwv
Mt. Wrangell valley-fill and basin lavas
Moderately to highly porphyritic, two-pyroxene high-silica andesite flows mineralogically and chemically identical to Mt. Wrangell shield lavas.
Whole rock K/Ar ages range from 25 ka to 270 ka
Qwu
Mt. Wrangell shield and valley fill lavas, undifferentiated
Mt. Wrangell shield and valley fill lavas, undifferentiated.  Restricted to exposures in nunataks that were not visited on the upper slopes of Mt. Wrangell.
Qah
Medium gray, slightly to moderately porphyritic andesite flows containing phenocrysts of plagioclase, orthopyroxene, hornblende, and traces of clinopyroxene and olivine in a cryptocrystalline to plagioclase rich groundmass.
Qba
Basaltic andesite flows
Dark gray, slightly porphyritic basaltic andesite flows containing phenocrysts of olivine, and a trace of clinopyroxene in a groundmass consisting of plagioclase laths.
Lava flows, pyroclastic deposits, and breccias, undifferentiated
Lava flows, pyroclastic deposits, and breccias, undifferentiated.  Chiefly a variety of dark brownish gray andesite lava flows.
Whole rock K/Ar ages of 1580 ka and 980 ka from andesitic lava flows
Qwlf
Flow and pyroclastic rocks from Mt. Wrangell - Dacite / andesite flows
Flows of dacite and andesite (?).  Rock is medium gray, locally vesicular, and contains phenocrysts
Qsl
Lava flows from Mt. Sanford
Lava flows exposed beneath glacial deposits
Wrangell Lava - Basalt and basaltic andesite flows
Dense flows with localized columnar jointing.  Gray olivine basalt.  Originated from vents in s.e. corner of map area.
K-Ar date of equivalent rocks in A-5 is 0.89 +/- 0.21 m.y.
Qabf
Wrangell Lava - Andesite and basaltic andesite flows
Thin to medium flows with oxidized dark-red scoraceous tops and bottoms.  Gray in color, with sparse olivine, hypersthene, and plagioclase phenocrysts.  Apparently related to an extensive sequence of flows in Nabesna A-5 quadrangle, where presumed local
Qwws
Wrangell volcano - Shield lavas
Chiefly andesite
Qdad
Wrangell Lava - Dacite and Andesite Domes and Flows
Broad, irregular-topped piles of massive columnar-jointed lavas.  Rocks are chiefly dark-gray to black andesites and dacites containing small phenocrysts.  Source local, probably in part extruded beneath ice cover
Qgbf
Wrangell Lava - Mt. Gordon Basalt and Andesite Flows
Thin flows with oxidized dark-red scoriaceous tops and bottoms.  Fresh rocks are dark gray and contain abundant phenocrysts
Qpaf
Wrangell Lava - Porphyritic Andesite and Dacitic Andesite Flows
Medium, dark-gray to black vesicular flows chiefly of two-pyroxene andesite.  Rocks contain abundant, large conspicuous phenocrysts.  Source unknown, probably local
Wrangell Lava - Basalt and Basaltic Andesite Flows
Dense thin to thick extensive flows, locally exhibiting pronounced columnar jointing.  Rocks are chiefly gray to dark-gray olivine basalts containing abundant phenocrysts.  Indicated source areas are the Ice Fields Plateau, Jaeger Mesa, and an eruptive c
K-Ar date on whole rock indicates age of 0.89 +/- 0.21 my
Wrangell Lava - Andesite Flows
A variety of medium to thick andesite flows apparently from a number of local but largely unknown source areas.  Rocks range from light to dark gray and are not conspicuously porphyritic
K-Ar date on plagioclase indicates age of 1.46 +/- 0.03 my
Qbt
Wrangell Lava - Basalt Tuff
Chiefly palogonitized air-fall lapilli tuff and ash and accretionary lapilli in beds and massive structureless tuff and block breccia.  Rocks are semi-indurated and characteristically buff to yellow orange.  Block, lapilli, and ash fragments consist whol
Qmbf
Wrangell Lava - Massive Basaltic Andesite Flow
Massive flow(s) of dense to vesicular basaltic andesite exhibiting pronounced columnar jointing.  Rocks are dark gray to black and contain abundant phenocrysts.  Unit caps north end of Lakes Plateau.  Source is probably local
Wrangell Lava - Basalt
Short flows and small irregular masses intimately associated with, and probably the extrusive equivalent of the palagonitic basalt tuffs (Qbt) in the Ice Fields Plateau area.  Rocks are dark gray to black and contain abundant olivine phenocrysts
Wrangell Lava - Andesite and Basaltic Andesite Flows
Flows with dark-red scoriaceous tops and bottoms.  Consists chiefly of gray to dark-gray flows containing sparse phenocrysts.  Source is local, apparently under the present ice cover in the n.e. part of the Ice Fields Plateau
Qtbf
Wrangell Lava - Thin Basalt and Basaltic Andesite Flows
Three eruptive flow centers recognized.  Similar to Mt. Gordon (Qgbf) and the young cinder cones (Qbc), but significantly older
Qws
Sanford volcano - Lava flows
Capitol volcano - Shield and intracaldera lavas
Qsp
Mount Sanford volcano -- Dacite pyroclastic flow
Mount Sanford volcano, dacite pyroclastic flow
Qdb
Dacite block and ash deposit
Contains blocks chiefly of light gray, porphyritic dacite as much as 2 m in diameter in a matrix of light gray to very light gray ash.
Qpf
Pyroclastic flow
Pale yellowish brown to moderate yellowish brown pyroclastic flow containing abundant bombs, scoria, and pumice.
Whole rock K/Ar age of 342 ka from a scoria bomb
Qht
Ho-Hum dome complex -- Dacite tephra
Ho-Hum dome complex.  Dacite tephra
Tuff
Chiefly palagonitized air-fall lapilli tuff, accretionaly lapilli, and ash.
Qwp
Flow and pyroclastic rocks from Mt. Wrangell - tuff and ash
Light-buff to light-gray deposits of tuff and probably ash flows
Qafp
Ash flow and pumice deposits from Mt. Wrangell or Mt. Drum
Semi-indurated rocks are light gray and consist of unsorted blocks, pumice, and ash of hornblende dacite generally overlying finer grained and stratified airfall beds of same composition.  Upper 20 m. form bold light-gray cliffs with weakly developed col
Wrangell Lava - Basalt tuff
Palagonitized air-fall lapilli tuff and ash, and accretionary lapilli in beds from 1 cm to 1 m in thickness.  Rocks are semi-indurated and characteristically buff to yellow orange.  Block, lapilli, and ash consist wholly of glassy scoria.  Source is prob
Qsdf
Sanford debris flow deposits
Debris derived from collapse of a dome on Sanford Volcano.  Flow traveled a great distance down the Sanford Glacier/River valley to confluence with the Copper River
QTa
Andesite mudflows, hyaloclastites, tephra, and flows
Pleistocene or Pliocene
Qdc
Dacite debris apron
Blocks and smaller fragments of hornblende dacite in crudely layered deposits.
Qcf
Chetaslina volcanic debris flow
Multi-colored, voluminous debris avalanche deposit containing megablocks of both porphyritic and aphanitic andesite lava, hydrothermally altered lava, volcanic breccia, pyroclastic flow deposits, lacustrine sediments, and glacial deposits.
Qvd
Volcaniclastic deposits - Volcanic debris flows
Includes the Chetaslina volcanic mass-flow deposit exposed along the Chetaslina and Copper Rivers and the Sanford volcanic debris flow exposed along the Sanford and Copper Rivers
Volcanic debris flow
Qda
Volcanic avalanche deposits
Nadina volcanic avalanche, landslide, and glacial deposits, undifferentiated
Mt. Drum volcano.  Chiefly varigated, crudely stratified and poorly sorted juvenile bombs, pumice, and ash and blocks of andesite and dacite.  Deposits are locally covered by, and mixed with, glacial drift.
Qva
Volcanic avalanche deposits of Nadina Valley
Semiconsolidated and crudely stratified deposits of unsorted volcanic rock debris.  Deposits range from light gray to buff to light shades of pinkish gray, green, and lavender and consist chiefly of fresh-appearing gray to buff blocks, pumice and ash of
Volcaniclastic deposits - Pyroclastic flows
Includes the extensive Nadina hot avalanche deposit from Mt. Drum and a pyroclastic flow (0.3 Ma), probably from Mt. Drum, at the junction of the two forks of the Chetaslina River
Qsh
Hyaloclastite
QTvg
Wrangell Lava - Volcanic gravel
Quaternary and Tertiary, Pleistocene, Pliocene, and Miocene
Unconsolidated to poorly consolidated.  Totally unsorted diamicton, with boulders of lava and basement rocks as much as 1 m in diameter to well-bedded, locally sorted volcaniclastic debris that may have been fluvially reworked.  Where semi-consolidated,
Qbc
Cinder cones and associated flows
Cinder cones
Qabv
Wrangell Lava - Andesite and basalt scoria
Red to black cinder cones, less than 500 m in diameter.  Usually identifiable from air photographs
Cinder cones, flows, and tuffs
Chiefly olivine basalt and basaltic andesite
Wrangell Lava - Basalt Cinder Cones
Basalt and basaltic andesite cinder cones.  Chiefly scoria, blocks, spindle bombs, and lapilli intermixed with spatter debris, agglutinates, and minor thin flows.  Many cones still retain original form
Qdac
Wrangell Lava - Dacite Cinder Cone
Chiefly dense glassy scoria.  Rocks are dark gray and contain phenocrysts
K-Ar on plagioclase indicates age of 1.34 +/- 0.20 my
Qrc
Wrangell Lava - Rhyolite Cinder Cone and Nuee Ardente Deposits
Cinder cone consists chiefly of unconsolidated rubble of dense glassy blocks, pumiceous scoria, and lapilli.  Nuee andente deposits composed largely of bread-crust blocks in a matrix of unconsolidated ash and lapilli.  Rocks are buff to light gray and co
Qzaf
Second-cycle cone-building flows - Two-pyroxene andesite
Two-pyroxene andesite and minor two-pyroxene dacite flows.  Flows are from 1 to 20 m thick, with scoriaceous tops and bottoms, and are locally highly vesicular.  Rocks are dark gray to meduim brownish gray.  They contain small phenocrysts
Qzuf
Second-cycle cone-building flows - Undivided
Undivided andesite and dacite flows
Qafb
Flows, flow breccias, and tuff
Thin to thick flows, chiefly of andesite and dacite composition, interlayered with massive breccias, palagonitized airfall beds, and probably lahars.  Deposits of buff-colored crystal-lithic tuff and breccia containing clasts of plagioclase and hornblend
Wrangell Lava - Andesite flows
Medium to thick augite-hypersthene-olivine-bearing andesite flows from local but unknown sources.  Light to dark gray rock; not conspicuously porphyritic.
K-Ar date of similar rocks indicates age of 1.46 +/- 0.03 m.y.
Qadf
Wrangell Lava - Andesite and dacite (?) flows
Thick, often glassy porphyritic flows with plagioclase the most common phenocryst.  Flows exhibit small-scale but pronounced columnar jointing.  Sources unknown, probably local
Dacite flows of Snider Peak
Massive dark-gray-weathering hornblende-rich flows that radiate from the general area of Snider Peak dome.  Flows appear to consist of complex multiple-flow cooling units suggesting possibility of more than one source.  They locally contain abumdant xeno
Qzdf
Second-cycle cone-building flows - Thick lobate flows of dacite
Thick lobate flows of dacite and minor rhyodacite that form massive piles.  Rocks are light to pinkish medium gray, weather dark reddish brown, and are porphyritic with phenocrysts
Qzof
Second-cycle cone-building flows - Olivine-bearing two-pyroxene dacite
Olivine-bearing two-pyroxene dacite and minor two-pyroxene andesite flows.  Source unknown.  Flows are thick and massive with locally pronounced columnar jointing.  Rocks are medium to dark gray and contain small phenocrysts
Qdaa
Wrangell Lava - Dacite Andesite Agglutinate Flow
Extensive single flow with well-formed columnar joints and black glassy base.  Rocks are gray to black and are mineralogically similar to unit Qdac, but contain abundant inclusions of both vitric and lithic volcanic debris.
Qdaf
Wrangell Lava - Dacite and Dacitic Andesite Flows
Massive, thick flows of dense black glassy lava
Wrangell Lava - Dacite Flow
Massive single flow unit, with dark-gray glassy base, light-gray crystalline interior, and vapor-phase vesicular top.  Rocks contain small phenocrysts
Wrangell Lava - Rhyodacite
Thick, massive flows and irregular domelike masses locally exhibiting highly contorted columnar jointing.  Rocks are light gray to pinkish gray and contain altered hornblende
Qrb
Wrangell Lava - Rhyodacite Tuff Brecia
Massive, structureless palagonitized breccia containing blocks and smaller fragments of rhyodacite.  Breccia probably represents an ice-flow contact deposit
Qrf
Rhyolite flow
Remnant of flow-banded massive and glassy rhyolite flow that apparently was extruded from rhyolite dome (Qrd).  Rock is light gray with small phenocrysts
QTb
Basalt dikes and sills
Quaternary or Tertiary
Basalt dikes and sills, possibly related to Wrangell Lavas
Qja
Jarvis volcanic complex -- Andesite flows
Jarvis volcanic complex.  Andesite flows; undifferentiated lava flows and minor lahars and flow breccias.
Qjb
Jarvis volcanic complex -- Basalt flows
Jarvis volcanic complex.  Basalt flows
Qwj
Jarvis volcanoes - Shield and intracaldera lavas
Qwr
Wrangell Lava (rhyolite cinder cone)
Rhyolite cinder cone and associated nuee ardente deposits
Collapsed dome
Qsi
Shallow plutons
Qdd
Dacite domes
Qdr
Rhyolite domes
Qsr
Rhyodacite dome and flow
Mount Sanford volcano -- Dikes, undifferentiated
Mount Sanford volcano, dikes, undifferentiated
Qh
Ho-Hum Creek dome complex
Ho-Hum dome complex.  An andesite-dacite dome-flow center northeast of the north Jarvis eruptive center.  Complex consists chiefly of an older, central dome and flows of hornblende dacite and younger flows of andesite and dacite that exhibit mixed magma
Qha
Ho-Hum dome complex -- Quartz-bearing high silica andesite flow
Ho-Hum dome complex.  Quartz-bearing high silica andesite flow
Qhad
Ho-Hum dome complex -- High silica andesite and dacite flows
Ho-Hum dome complex.  High silica andesite and dacite flows
Qhdd
Ho-Hum dome complex -- Dacite dikes
Ho-Hum dome complex.  Chiefly northerly trending dikes apparently restricted to central part of dome complex.
Qhp
Ho-Hum dome complex -- Dacite central plug
Ho-Hum dome complex.  Dacite central plug
Qhdi
Ho-Hum dome complex -- Dacite shallow intrusion (?)
Ho-Hum dome complex.  Dacite shallow intrusion (?)
Qhd
Ho-Hum dome complex -- Dacite dome and flows
Ho-Hum dome complex.  Undifferentiated dome rock and flows in central part of complex.
Qjdf
Jarvis volcanic complex -- Dacite flows
Jarvis volcanic complex.  Dacite flows
Qjd
Jarvis volcanic complex -- Dikes and plugs
Jarvis volcanic complex.  Dikes and plugs; dikes examined were dark gray, porphyritic, olivine-bearing two pyroxene andesites.
Qdi
Dacite plugs
Light gray, moderately porphyritic hornblende dacite containing phenocrysts of plagioclase, hornblende, and traces of orthopyroxene in a cryptocrystalline to microcrystalline groundmass.
Dacite flow dome
Light gray porphyritic hornblende dacite containing phenocrysts of plagioclase and hornblende that is locally rimmed with black oxides in a cryptocrystalline groundmass.
Qod
Dacite intrusion
Light olive-gray to greenish-gray porphyritic, containing phenocrysts of plagioclase, hornblende, and biotite in a cryptocrystalline groundmass locally flooded by calcite.  Description from principal exposure to the north in the Gulkana A-1 quadrangle wh
K-Ar age of 1.35 Ma
Qsrd
Rhyodacite dome of Snider Peak
Remnant core of rhyodacite dome representing one of the latest stages of eruptive activity of Mt. Drum volcano.  Rocks are light gray to light buff gray, have a sugary texture, and are locally vesicular
Qldd
Late dacite domes and associated flows
Six distinctive hornblende-biotite dacite domes and associated short massive flows mark climax of second cycle of eruptive activity of Mt. Drum volcano.  Dacites are light to medium gray and conspicuously porphyritic with abundant phenocrysts
Qedd
Early dacite domes and associated flows
Three hornblende-dacite domes.  Rocks of domes 1 and 2 are light to dark gray and porphyritic with abundant phenocrysts.  Dome-3 rocks are generally coarser grained with common to abundant biotite.
Qui
Undifferentiated plugs and small intrusive bodies - Dacite
Chiefly light to medium gray dacite rocks with phenocrysts.  One intrusive rhyodacite is light gray and contains phenocrysts
Dacite dikes
Generally associated with rhyolite and rhyodacite domes.  All dikes sampled are medium to dark gray and sparsely porphyritic with small phenocrysts
Qrd
Four conspicuously light-colored rhyolite domes that are deeply dissected by erosion and expose light-colored cores cut by numerous dark-colored dacite dikes.  Rocks are light gray, pink, and buff, and weakly porphyritic with small phenocrysts
Qrdd
Rhyodacite dome
Dissected hornblende rhyodacite dome probably related in age to rhyolite domes (Qrd).  Rock is light gray with small phenocrysts
Qwsr
Sanford volcano - Dome
Rhyolite dome and flow
Wrangell Lava - Dacitic Andesite and Dacite Flows
Flows with minor interbedded tuffs and breccias representing the main cone-building stage of Jarvis volcanoes.  Rocks are dark gray to pinkish gray.  Cut by numerous dark-colored andesite dikes
K-Ar date on plagioclase indicates age of 1.63 +/- 0.42 my
Qwjd
Jarvis volcanoes - Dome
Chiefly dacite
Rhyolite dikes and laccoliths
Qtp
Andesite plug
Medium gray, plagioclase-rich andesite porphyry containing phenocrysts of fresh, euhedral plagioclase, clinopyroxene, and orthopyroxene in a cryptocrystalline groundmass.
Whole rock K/Ar age of 529 ka
Qcd
Andesite-dacite domes (?) and breccias
Andesite-dacite domes (?) and breccias.  Light gray domes ranging from andesite containing plagioclase, orthopyroxene, clinopyroxene, and olivine to porphyritic dacite containing phenocrysts of plagioclase, clinopyroxene, orthopyroxene, and hornblende in
Whole rock K/Ar age of 874 ka
Radial dike swarm and plugs
Qci
Andesite dikes
Two dikes, of the five observed were accessible and sampled.  Both are dark gray slightly porphyritic andesite.
QTma
Wrangell Lava - Massive andesite, dacitic andesite flows and agglutinates
100 m thick flows with pronounced columnar jointing exposed in s.w. corner of map.  This is the same unit that makes up all the high Tanada peaks in B-6.  Flow rocks are gray.  Agglutinates are green with clasts of gray glassy dacitic andesite.  Rocks lo
QTwi
Older volcanic and sedimentary rocks - Icefield flows
Massive flows of high silica andesite capping the Icefields Plateau
QTwt
Tanada volcano
Quaternary and Tertiary, Pleistocene and Pliocene
Shield and intracaldera lavas, chiefly andesite
QTw
Wrangell Lava
Quaternary and Tertiary?
At least 2,000 m of flows, tephra, and minor sedimentary rocks in northeastern Valdez quadrangle.  Consists of mainly pyroxene andesite but ranges from basalt to dacite.
Dates as old as 10 Ma in adjacent Nabesna quadrangle, thought to be largely Quaternary in Valdez quadrangle.
Quaternary and Tertiary
Calc-alkaline volcanic province including flows, tephra, and sedimentary units.  Derived from shield or composite stratovolcano flows, or their satellite centers.   Flows mainly andesite, also range from basalt to rhyolite, and less abundant dacite.  Loc
Fossil leaves from Frederika Formation indicate a Miocene age
K-Ar dates of tillite of 2.7 and 10 m.y.
Wrangell Lava (older part)
Undivided andesite and basaltic andesite flows, dacite flows andÿdacite domes, tuffs and breccias, and dacitic andesite agglutinate flows.
K-Ar dates suggest a minimum of 10 m.y.
Qnf
Volcanic rocks-Nathlie Mountain eruptive center
Flows, breccias, and sedimentary rocks
QTu
Volcanic rocks
Pleistocene and Pliocene (?)
Volcanic rocks, undifferentiated
QTtd
Lavas of Tumble Creek -- Dacite flows?
Lavas of Tumble Creek.  Dacite flows?
QTta
Lavas of Tumble Creek -- Andesite and basaltic andesite flows, lahars, and hyaloclastites
Lavas of Tumble Creek.  Andesite and basaltic andesite flows, lahars, and hyaloclastites
Qwe
Early Mt. Wrangell lavas
Early Mt. Wrangell lavas.  The flows north of the Chetaslina Glacier are porphyritic, olivine-bearing, two-pyroxene andesites exhibiting magma mixing features.  The isolated flows are also olivine-bearing tow-pyroxene porphyritic to seriate andesites.
K/Ar age of 690 ka
QTaf
Extensive flows with oxidized scoriaceous tops and bottoms.  May include younger thin basalt flows from local eruptive centers.  Locally, rocks are altered to chlorite and clay minerals.  Distiguishing characteristics to QTau include a predominance of ol
QTad
Wrangell Lava - Andesite and acitic andesite dome
Gray rocks with plagioclase phenocrysts in a fine grained glassy matrix.  May be associated with younger rocks of QTau and/or QTaf
QTav
Wrangell Lava - Old andesite and basaltic (?) scoria
Zones of bright-red breccia and bomb fragments.  No topographic expression of small cone
QTau
Wrangell Lava - Andesite flows, flow breccias, and volcaniclastic rocks, undifferentiated
Gray hypersthene andesite flows with red scoriaceous tops and bottoms.  Holocrystalline rocks with labradorite phenocrysts in a trachytic groundmass of plagioclase, minor clinopyroxene, and traces of olivine.  Collective package of flows (< 5m) may excee
K-Ar age of 2.77 +/- 0.10 m.y.  Similar rocks in C-5 yielded an age of 1.97 +/- 0.15 m.y.
QTdb
Wrangell Lava - Basalt and andesite dikes
Small, nearly vertical fine-grained nonporphyritic olivine basalt and hypersthene andesite dikes.  Glassy with local columnar jointing.  Dikes almost certainly represent more than one episode of intrusion, perhaps widely separate in time
Tb
Wrangell Lava - Basalt flows
Tertiary, Miocene
Vesicular, f. - m.g., locally porphyritic flows.  Rocks locally chloritized and altered to clay minerals
K-Ar date yielded 13.9 +/- 0.8 m.y.
Quaternary and Tertiary, Holocene, Pleistocene, Pliocene, and Miocene
Differentiated calc-alkaline lava flows of andesite, basaltic andesite, and olivine andesite with minor volcanic conglomerate locally near the base.  The lavas are dark gray and weather medium brown to dark yellowish brown
Qbb
Wrangell Lava - Basalt and Basaltic Andesite Breccias
Oxidized basaltic breccias apparently from old cinder cones.  Fresh rocks are dark gray to black and contain phenocrysts
QTab
Wrangell Lava - Andesite Breccia
Quaternary and Tertiary, Pleistocene, Pliocene, and older?
Massive sequence of light-gray to drab-brown fine to coarse structureless breccia
QTbf
Extensive flows with oxidized dark-red scoriaceous tops and bottoms.  Rocks are gray and contain small phenocrysts.  Locally matrix is altered to chlorite and clay minerals
QTuf
Wrangell Lava - Undifferentiated Flows, Tuffs, and Breccias
Chiefly flows of andesite, basaltic andesite, and basalt interbedded with a variety of pyroclastic deposits, volcanic mud flow deposits, and probably some volcano-glacial deposits.  Rocks are locally altered to chlorite and clay.  Sources from a number o
K-Ar from correlative volcanic strata in B-5 suggest an age apan of 1.0 to 2.5 my
Older volcanic and sedimentary rocks - Lava flows
Chiefly andesite and dacite.  Includes the sedimentary non-marine Frederika Formation that occurs locally at the base of the Wrangell volcanic field in the southern Wrangell Mountains
QTi
Intrusive rocks
Qbp
Plug
Small plug of olivine-bearing, sparsely porphyritic basaltic andesite.
QTai
QTwr
Wrangell Lava (rhyodacite and rhyolite)
Rhyodacite and rhyolite domes, associated, nuee ardente and air-fall deposits (both locallized), local mudflow and tillite (?) deposits, and pumice lapilli tuff
Qni
Dacite pluton
Qwd
Dacite flows
QTrd
Rhyolite dome
Rhyolite dome exposed chiefly in adjacent Nabesna A-5 quadrangle.
QTda
Undifferentiated intrusive dacite and associated breccias
Intrusive bodies consist of light- to medium-gray porphyritic dacite containing phenocrysts.  Associated breccias are massive, brownish-gray, reddish-brown, and mauve rocks containing angular clasts of porphyritic dacite
QTrv
Wrangell Lava - Rhyodacite breccia
Strongly brecciated zones, probably representing vent areas, less than 100 m in diameter.  Consists of rocks probably related to QTr.  Minor dacite to rhyolitic rocks.  Locally contains small glassy plugs and scoria.  No topographic expression of cone
QTr
Wrangell Lava - Rhyodacite domes and associated flows
Massive gray rocks that weather pink-gray tan.  Commonly porphyritic with abundant phenocrysts of plagioclase (60%), hypersthene, and minor oxyhornblende and altered biotite.  Locally devitrified and altered to chlorite and clay minerals.
Plagioclase K-Ar date is 3.74 m.y.
ALT-BIO
QTdr
Wrangell Lava - Rhyodacite dikes
Medium-grained, locally pophyritic rocks with phenocrysts.  Dikes range from 1 to 29 m in width and often occur in subparallel sets.  Apparently associated with rhyodacite domes (QTr).  Host andesites (QTau) locally contain sufides, chiefly pyrite, near
QTru
Wrangell Lava - Rhyolite breccia and flows, undifferentiated
Presumably formed from debris shed from domes (QTrd).  Occur in poorly exposed dome margins
QTrt
Wrangell Lava - Rhyolite and rhyodacite pyroclastic deposits
Buff to light gray air-fall and nuee ardente deposits, locally reworked by water.  Presumably associated with rhyolite domes (QTrd).
QTrf
Wrangell Lava - Rhyolite flow
Massive, light-gray, devitrified, microcrystalline rocks with red and black vitrophyre phases exhibiting pronounced flow banding.  Presumably from rhyolite domes (QTrd)
Wrangell Lava - Rhyolite domes
Light gray to buff, massive rocks with small phenocrysts of potassium feldspar, oxyhornblende, and altered biotite in a cryptocrystalline groundmass
Older volcanic and sedimentary rocks - Domes and intrusive rocks
Quaternary (Pleistocene) and Tertiary (Pliocene and Miocene)
Chiefly dacite and rhyolite
Wrangell Lava - Rhyolite Dome
Light-colored dome with rubble carapace.  Rocks are light gray to buff and fine-grained containing sparse altered hornblende
Wrangell Lava - Rhyodacite Dome
Gray, rubble-covered dome.  Relation to other volcanic units is not certain.  Rocks are light gray to gray and contain small altered hornblende
Wrangell Lava - Rhyolite Flows and Domes
Extensive flows and domes of gray to pinkish-gray devitrified rhyolite with black porphyritic glassy base.  Devitrified rock contains sparse phenocrysts.  Glassy base contains abundant plagioclase
K-Ar date on plagioclase indicates age of 2.85 +/- 0.05 my
Ts
Sedimentary rocks
Cenozoic
QTy
Yakataga Formation
Pleistocene to Miocene
Interbedded gray to dark-gray and greenish-gray siltstone, mudstone, and sandstone predominate in lower third of formation. Till-like diamictite is interbedded with siltstone and sandstone in all but lowest part of formation and is the dominant rock type
Contains an abundant marine megafauna and microfauna
Consists of diverse marine and glaciomarine clastic rocks. Interbedded gray to dark-gray and greenish-gray siltstone, mudstone, and sandstone predominate in lower third of formation. Till-like diamictite dominant rock type in upper part of formation.
Pleistocene(?), Pliocene and Miocene
More than 4,000 m of gray to dark-gray siltstone and mudstone, interbedded with massive subquartzose sandstone, diamictite (conglomeratic sandy mudstone or tillite), and conglomerate.  Sandstone less than 25 to 30 percent of surface sections.
Contains a moderately abundant molluscan megafauna and foraminiferal microfauna.  Also rare fossil leaves and vetebrates.
Tk
Kulthieth formation
Eocene
Unit consists of massive to thin-bedded coal-bearing, arkosic sandstone, dark-gray to black carbonaceous siltstone and shale, and minor coal.  Sandstone and shale ratios in measured sections average about 1:1.  The sandstone varies from massive intervals
plants, and mollusks
Tr
Redwood Formation
Pliocene to Oligocene?
Lower sandstone member: about two-thirds thick-bedded sandstone and one-third silty sandstone and siltstone. Upper member: about one-half siltstone, mudstone and claystone, the rest is conglomerate and sandstone.
Oligocene (?) and Miocene
Marine siltstone, sandstone, and conglomerate.  The sandstone member consists of about two-thirds thick-bedded sandstone and one-third silty sandstone and siltstone.  The characteristic conglomeratic beds show complete gradation from coarse, clast-suppor
mollusks, and foraminifera
Tp
Poul Creek Formation
Miocene to Eocene
Shale and minor sandstone that is, in part, glauconitic, rich in organic material, and intercalated with intrabasinal, water-laid alkalic basaltic tuff, breccia, and pillow lava.
Tps
Sedimentary rocks, undivided
Tertiary, Oligocene and early 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 include
Poul Creek Formation: Sedimentary rocks, undivided
Miocene, Oligocene, and Eocene
Concretionary, pyritic, glauconitic, reddish-weathering, dark-gray to greenish-gray siltstone, claystone, and sandstone; shale that is rich in organic material; gray calcareous sandstone; local thin interbeds of basaltic tuff.
Poul Creek Formation:  Sedimentary rocks, undivided
Concretionary pyritic, and glauconitic reddish-weathering, ark-gray to greenish-gray siltstone, claystone, and sandstone with subordinate dark-brown, laminated organic-rich shale, and gray calcareous sandstone; also includes thin interbeds of basaltic tu
Sedimentary rocks, undivided (Poul Creek Formation)
Oligocene
Single outcrop consisting of 10 m of intensely sheared, reddish-brown weathering, dark-greenish-black glauconitic and pebbly sandstone containing abundant mafic volcanic detritus.  Thought to be correlative with Poul Creek Formation
Tpv
Volcanic rocks, undivided
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). [Note simila
Tt
Tokun Formation
Tertiary, Eocene
Consists predominantly of concretionary siltstone and lesser, variable amount of interbedded sandstone, chiefly in lower part of formation. Siltstone generally is medium to dark gray and nearly massive; locally, thin beds and lenses of lighter gray, brow
Contains a very sparse marine megafauna
Consists predominantly of concretionary siltstone and lesser, variable amount of interbedded sandstone. Siltstone is medium to dark gray and nearly massive. Spheroidal calcareous concretions as much as 1 m in maximum dimension are distributed randomly or
Oligocene and Eocene
A transgressive marine sequence.  Consists predominantly of concretionary siltstone with a lesser and variable amount of interbedded sandstone, chiefly in the lower part of the formation.  The siltstone generally is medium to dark gray and nearly massive
crabs, and mollusks
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.  Occurs in limited outc
foraminifers
Dense hard dark-gray siltstone. Where siltstone is carbonaceous, it has a coalike appearance; where its calcareous, it may be variegated from reddish brown to pale green
The dominant lithology is dense hard dark-gray siltstone.  Where the siltstone is carbonaceous, it has a coaly appearance; where it is calcareous, the siltstone may be variegated in shades of reddish brown to pale green and usually contains foraminifers.
foraminifers, and mollusks
Kulthieth Formation
lncludes 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:shale ratios in measured sections (Martin, 1908) average about 1:1. Sandston
Contains a sparse marine megafauna and locally abundant plant fossils
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. Commonly intensely deformed into imbricated stacks of fault-bounded chevron folds.
Consists of massive to thin-bedded coal-bearing, arkosic sandstone, dark-gray to black carbonaceous siltstone and shale, and minor coal.  Sandstone and shale ratios in measured sections average about 1:1.  The sandstone varies from massive intervals as m
Tertiary, Eocene and late Paleocene
At least 3,000 m of orange weathering light-gray feldspathic to lithofeldspathic sandstone and calcareous sandstone interbedded with dark-gray siltstone, pebble conglomerate, and many thin beds of coal.  Commonly well-indurated with bituminous rank coal.
Contains a sparse warm water molluscan megafauna and locally abundant sub-tropical plant fossils
Tk?
Kulthieth Formation(?)
Siltstone of Oily Lake
Dark-gray, siliciceous, organic-rich siltstone.  Exposed only near Oily Lake in the Samovar Hills
Tos
Orca Group -- sedimentary rocks, undivided
Paleocene and Eocene?
Marine argillite, siltstone, sandstone, and conglomerate.  Argillite and siltstone are more abundant than the coarser-grained rocks.  Well-bedded, repetitive finer-grained and coarser-grained strata; primary sedimentary features are diagnostic of deposit
Orca Group -- Sedimentary rocks, undivided
Tertiary, Eocene and Paleocene
Very thick, complexly deformed, monotonous sequence of thin- to thick-bedded turbidites consisting of sandstone, siltstone, and mudstone; metamorphosed to zeolite or prehnite-pumpellyite facies. Sandstone is feldspathic to litho-feldspathic. Abundant pri
In Prince William Sound area to the west, contains sparse planktonic foraminifers, fossil crabs, pelecypods, and gastropods
Eocene and Paleocene
Very thick, complexly deformed monotonous sequence of thin- to thick-bedded turbidites consisting of sandstone, siltstone, and mudstone; metamorphosed to zeolite or prehnite-pumpellyite facies. Abundant sedimentary features indicate deposition from sedim
planktonic foraminifers, fossil crabs, pelecypods and gastropods
Eocene (?) and Paleocene
A sequence of thin- to thick-bedded sandstone, siltstone, and mudstone.  Abundant sedimentary structures, such as graded bedding, crossbedding, and ripple marks, along with flute, groove, and load casts, indicate deposition from turbidity currents.  Sand
Pollen:  Alnus (Alder)  Foraminifers: Globogerina sp., G. senni, Globogerina sp. (hispid), Globorotalia sp.  Echinoids:  Holaster sp. ?Hypsopygaster sp., Nucleopygus
Tots
Orca Group -- Tuffaceous sedimentary rocks
Tuffaceous sedimentary rocks, volcaniclastic sandstone, and minor chert.  Locally, these rocks contain abundant radiolarians and diatoms of probable Tertiary age (table 2).  South of the Martin fault, this unit also includes minor pillow basalt and abund
Diatoms: Arachinodiscus cf., A. ehrenbergii, Trinacria ef., T. pileclus  Silicoflagellates:  ?Corbisema geometrica, ?Corbisema hastata, ?Corbisema triacontha, Dictyocha aspera, Navoculopgis constricta
ORCA GROUP:  A sequence of thin- to thick-bedded sandstone, siltstone, and mudstone.  Abundant sedimentary structures, such as graded bedding, crossbedding, and ripple marks, along with flute, groove, and load casts, indicate deposition from turbidity cu
ORCA GROUP:  Tuffaceous sedimentary rocks, volcaniclastic sandstone, and minor chert.  Locally, these rocks contain abundant radiolarians and diatoms of probable Tertiary age (table 2).  South of the Martin fault, this unit also includes minor pillow bas
Orca Group: --Tuffaceous sedimentary rocks
Tovs
Orca Group -- Interbedded sedimentary and volcanic rocks
Variable proportions of interbedded, tholeiitic basalt (Tov) and turbidites (Tos).
Variable proportions of interbedded, tholeiitic basalt and turbidites. Basalt--pillowed and massive flows, pillow breccia, and tuff. Turbitdites--mudstone, siltstone, and fossiliferous volcanogenic sandstone. Metamorphosed to zeolite or prehnite-pumpelly
Tosv
Orca Group -- Interbedded sedimentary and mafic volcanic rocks
Unit consists of locally variable amounts of volcanic and sedimentary rocks.  In some cases unit is marginal to thicker sequences composed of pillowed and massive basalt flows.  The lithologies are quite variable throughout the study area.  In Ragged mou
Foraminifers: Globigerina or Subbotina;  Globigerina sp. (?) Globorotalia sp.; Globigerina cf. G. senni, Globorotalia sp., ?Eoconuloides parvulus, Globigerina sp. (high spired), Globigerina sp. (hispid)
HFS
ORCA GROUP:  Unit consists of locally variable amounts of volcanic and sedimentary rocks.  In some cases unit is marginal to thicker sequences composed of pillowed and massive basalt flows.  The lithologies are quite variable throughout the study area.
Tops
Orca Group -- Pillow basalt and sedimentary rocks
ORCA GROUP:  Pillow basalt, massive basalt flows, minor volcanic breccia interbedded with sandstone, siltstone, and shale.  Distinguished from the interbedded sedimentary and mafic volcanics rocks unit on the basis of the predominance of pillow basalt in
Orca Group, turbidites
Tertiary, early Eocene and late Paleocene
Mudstone to sandstone, locally fossiliferous submarine gravity flows
Toc
Orca Group -- Conglomeratic sedimentary rocks
Very poorly bedded conglomeratic sandstone and argillite mantle the tops of volcanic sequences.  Conglomeratic rocks are very poorly sorted; clasts vary in size from granules to boulders and are supported by matrix.  Basal parts of conglomeratic frequent
Orca Group: Conglomerate
Massive, clast-supported, well-rounded pebble, cobble, and boulder conglomerate. Variable clast composition.
Orca Group:  Conglomerate
Ranges from matrix-supported pebbly mudstone and sandstone to massive clast-supported pebble, cobble, and boulder conglomerate.  The generally well-rounded clasts consist of various lithologies that have locally predominant types as follows:  greenstone,
Crab:  Branchioplax washingtoniana Pelecypod:  Acila decisa
ORCA GROUP:  Ranges from matrix-supported pebbly mudstone and sandstone to massive clast-supported pebble, cobble, and boulder conglomerate.  The generally well-rounded clasts consist of various lithologies that have locally predominant types as follows:
Czab
Olivine basalt and andesite
Ta
Andesite flows; Metamorphic Complex of Gulkana River
Tertiary (?)
Tif
Felsic to intermediate hypabyssal intrusive rocks
Dikes, sills, and small stocks, compositionally diverse, dacite predominates but rocks range from rhyodacite to quartz latite and andesite.
K-Ar age of 47 and 52 Ma reported as well as numerous 40 to 50 Ma ages and some as young as Pliocene.
Tsp
Andesite and basalt plugs(?)
Dark, generally aphanitic, dense andesite and basalt rock masses contained within breccias of unit Tsb.  Wrangell lava; Sonya Creek Shield volcano; ring fracture(?) related rocks
Tsf
Andesite flows and tephra
Dark, aphanitic lava flows and interlayered lapilli tuffs that overlie fragmental rocks of unit Tsb.  May include some basalt flows.  Wrangell lava; Sonya Creek Shield volcano; ring fracture(?) related rocks
Tsb
Andesite and basalt fragmental rocks
Dark volcanic breccias and agglomerates, all generally welded and minor mudflows that are locally palagonitized.  Breccias contain clasts as much as 5 m in diameter; agglomerates contain round and spindle bombs as much as 1 m long.  Aphanitic to locally
Tcc
Andesite cinder cones
Reddish, oxidized cinder and scoria.  West of Sonya Creek, unit may include thin andesite flows.  Wrangell lava; Sonya Creek Shield volcano; ring fracture(?) related rocks
Twl
Lavas of Wiki Peak
Extensive, thin to locally thick (as much as 35 m), lava flows and subordinate interlayered lahars and lapilli tuffs that show an aggregate thickness of more than 1000 m.  Basalt to dacite, but predominantly basaltic andesite and andesite.  Wrangell lava
20.0 +/- 0.6 my, K/Ar, whole rock from a flow high in intracaldera section
Tbc
Basalt cinder cone and flow
Red cinder cone and dark basalt flow.   Flow contains aligned microphocrysts of plagioclase, clinopyroxene, and olivine.  Wrangell lava; Sonya Creek Shield volcano; intracaldera(?) rocks
Tm
Mudflows(?)
Structureless to locally stratified mudflows(?) containing clasts of angular volcanic rock as much as 10 m in diameter and minor rounded clasts of exotic plutonic rock.  Unit appears to form basal unit in Sonya Creek caldera(?).  Wrangell lava; Sonya Cre
Tvu
Intracaldera(?) lavas, undifferentiated
Mainly lava flows of intermediate composition; also includes interlayered mafic flows, pryoclastic deposits, lahars, and tuffs.  Wrangell lava; Sonya Creek Shield volcano; intracaldera(?) rocks
Tsl
Aphanitic to porphyritic andesite and possibly dacite lava flows and minor interbedded mudflows and glassy agglomerates.  Flows are mostly flat-lying and are generally less than 10 m thick; aggregate thickness about 350 m.  Wrangell lava; Sonya Creek shi
Tsm
Andesitic mudflows
Thick (25 m), poorly sorted, and clast-supported mudflows and minor thin interbeds of mud-rich sand and gravel of andesite lava.  Unit may include a few thin andesite lava flows.  Aggregate thickness more than 230 m; base not exposed.  Wrangell lava; Son
Tsu
Shield lavas, undifferentiated
Mapped only along the north margin of the inferred caldera.  Chiefly south-dipping andesite lava flows, but includes a variety of flows and volcaniclastic rocks.  Thickness probably more than 500 m.  Wrangell lava; Sonya Creek shield volcano; shield rock
Tbpa
Prophyritic andesite flows
Very extensive and thick two-pyroxene andesite lava flows that exhibit well-defined vertical columnar jointing.  Coarsely porphyritic containing plagioclase, clinopyroxene, and orthopyroxene.  Minor lithic clasts and association with andesitic agglutinat
Tba
Andesite agglutinates
Locally extensive 2-pyroxene andesite agglutinates as much as 30 m thick.  Rock contains lithic clasts and, locally, streaks of glassy fiamme.  Unlike the associated columnar-jointed flows (Tbpa), the agglutinates are only sparsely porphyritic.  Wrangell
Tbl
Volcanic and volcaniclastic rocks, undifferentiated
Sequence of interlayered flows and lahars, chiefly andesite composition, and, locally, volcanic gravel and conglomerate.  Upper part overlies the dacite dome field and assoc. rocks (Tdh), but lower part appears to be intruded by dacite porphyry (Tdh), he
Tol
Andesite lavas and mudflows
A sequence of tilted and interlayered porphyritic to aphanitic andesite lava flows and mudflows that dip 20-30ø north.  Aggregate thickness about 1000 m, but base is not exposed.  Young Creek volcanic and volcaniclastic rocks
Two whole-rock K-Ar ages on single sample give ages of 18.6 and 19.1 Ma.  Too young, probably reset; overlain by Sonya Ck. shield lavas (20 Ma) and intruded and tilted by subvolcanic rocks (Tdd, 23 Ma)
Trl
Rocker Creek volcanic and volcaniclastic rocks, undifferentiated
Dark basalt to andesite lava flows and minor interlayered mudflows and maroon to dark-green volcanic siltstone, sandstone, and pebble conglomerate.  Structurally deformed; bedding dips 20ø to the southwest
whole-rock K-Ar age of 26 Ma from basalt lava flow
Tau
Older andesites and basaltic andesites, undivided
Pliocene
Older andesite and basaltic andesite, undivided
Trt
Rhyolite tephra
Bedded, light-colored, rhyolitic air-fall deposits locally as much as 25 m thick.  Exposed in the extreme northeast sector of caldera; may represent distal air-fall deposits of Twr.  Wrangell lava; Sonya Creek Shield volcano; intracaldera(?) rocks
Tpf
Dacite pyroclastic flow
Light-colored, paleovalley-filling dacite ash-flow tuff containing phenocrysts of plagioclase, quartz, and minor hornblende and clinopyroxene in a welded pumiceous groundmass.  Wrangell lava; Sonya Creek Shield volcano; intracaldera(?) rocks
Tsa
Dacite agglutinate
Extensive but relatively thin (25-35 m) dacite agglutinate consisting of densely welded flattened pumice, stretched glass fragments, and equidimensional lithic fragments exhibiting a well developed eutaxitic texture.  Agglutinate appears to be a single f
Trp
Rhyolite volcaniclastic rocks
Light-colored pyroclastic flows and tephra.  Pyroclasitc flows contain glassy and fine-grained breadcrust bombs in ash-rich matrix.  Source is probably the rhyolite dome of unit Trr.  Rocker Creek volcanic rocks
Twr
Rhyolite flow(s)
Thick (200 m), light-colored and intricately flow-banded rhyolite lava containing abundant, pristine black obsidian.  Locally includes as much as 2 m of overlying rhyolitic lapilli tuff and 10 m of rhyolitic volcanic sandstone.  Wrangell lava; Sonya Cree
Th
Hypabyssal rocks
Dacite, andesite, and rhyodacite porphyry.  Typically strongly porphyoritic.  Correlates with younger porphyry of Nabesna quadrangle and with hypabyssal rocks associated with the Wrangell Lava in Alaska and Canada.  Subdivision of unit Th of MacKevett (1
K-Ar on biotite of 3.8+0.8 m.y. and sanidine of 6.5+0.2 m.y.
MC006
Tsd
Dacite dome
Glassy, dense dacite dome exhibiting well-developed columnar joints.  Wrangell lava; Sonya Creek Shield volcano; ring fracture(?) related rocks
Rhyolite dome and plugs
Light-colored, crystal-poor, flow-banded rhyolite.  Rock contains a few percent of small plagioclase and biotite phenocrysts in a devitrified chalky matrix.  The dome, exposed north of Ptarmigan Lake, apparently was endogenous, and it structurally deform
Tdh
Dacite porphyry domes
Broad belt of at least eight coalesced endogenous and exogenous dacite domes that extends more that 19 km around and under the Sonya Creek shield volcano.
23 Ma, by K/Ar on hornblende from dome overlain by Sonya Creek intracaldera(?) rocks
Tdr
Light-colored, fine-grained rhyolite containing sparse microphenocrysts of plagioclase, hornblende, biotite, and locally, rosettes of black tourmaline.
Trr
Small light-colored dome or shallow intrusion that is locally highly brecciated.  Rock is fine grained and chalky and contains occasional quartz eyes.  Rocker Creek volcanic rocks
Late Tertiary, Pliocene
Dikes, sills, and small stocks of silica-rich subvolcanic phases of parts of the Wrangell Lava.  Comprise dacite and less abundant rhyodacite and andesite; rocks are very light gray to whitish and weather to buff, chalky white, or pale yellowish brown, g
K-Ar on hornblende from fresh dacite float from the Kuskulana Glacier moraine indicate an age of 3.8 +/- my
Basaltic to andesitic plugs and dikes
Tertiary, Miocene and Oligocene
Small basalt plugs and dikes.  Generally amygdaloidal and vesicular; may exhibit flow structures.  Generally too small to show on map.  Some of the basaltic rocks may be of Oligocene age based on correlation with  compositionally similar submarine flow a
Tertiary, Miocene and Oligocene(/)
Td
Dacite of Cape Saint Elias
Pliocene or Miocene
Prominent very pale gray dacite plug complex that forms Cape Saint Elias and Pinnacle Rock at southwestern end of Kayak Island. Dacite is very dense and hard and is conspicuously jointed. Microgranitic and porphyritic texture.
Whole-rock K-Ar age of 6.2 Ma
Rhyolite porphyry and granite
Pliocene(?) or Miocene(?)
Discordant hypabyssal plutons and related dikes at Mt. Owen and on east flank of Mt. Cook.  Vary from porphyritic to fine-grained, hypidiomorphic and equigranular.
Younger porphyry
Porphyries ranging from andesite to rhyodacite.  Dikes and sills with alteration.  Porphyries may represent hypabyssal equivalent of the older part of the Wrangell Lava
K-Ar data yields ages between 17 and 39 m.y.
Very dark andesite plug that may mark a principal eruptive area of the Sonya Creek volcano.  Rock is aphanitic, containing sparse microphenocrysts of plagioclase, orthopyroxene, and clinopyroxene.  Wrangell lava; Sonya Creek Shield volcano; intracaldera(
Wrangell Lava - Hornblende porphyry
Small, complex, intrusive, dacite to andesite porphyries.
K-Ar age from adjacent quad B-4 is 18.4 m.y.
Younger plutons - Wrangellia Terrane
Chiefly hornblende-feldspar and feldspar porphyry.  Some of the younger plutons may be related to Wrangell volcanism
K-Ar dates indicate ages of 17-39 Ma.
Poul Creek Formation: Volcanic rocks, undivided
Basaltic pyroclastic and flow rocks; locally interbedded with marine sedimentary rocks. Probably related genetically to mafic dikes, sills and plugs unit (Tm).
Poul Creek Formation:  Volcanic rocks, undivided
Basaltic pyroclastic and flow rocks including minor pillowed flows; locally interbedded with marine sedimentary rocks, including tuffaceous or glauconitic strata, probably genetically related to mafic dikes, sills, and plugs of the mafic plugs unit (Tm).
K/Ar date on whole rock of 31.2 + or - 1.3 Ma
Poul Creek Formation -- Volcanic rocks, undivided
Basaltic pyroclastic and flow rocks including minor pillowed flows; locally interbedded with marine sedimentary rocks, including tuffaceous or glauconitic strata, probably genetically related to mafic dikes, sills, and plugs of the mafic plugs unit (Tm)
Mafic dikes, sills, and plugs
Mafic dikes, sills, and plugs. Strongly altered intrusions of diabase, alkalic basalt, olivine basalt, and lamprophyre. Probably related genetically to extrusive volcanic rocks (Tpv) in Poul Creek Fm.
Mafic plugs
Oligocene (?)
Only includes mafic plugs in the eastern Cordova quadrangle west of Nichawak Mountain; mainly in the Blying Sound quadrangle.  Miller (1975) and Winkler and Plafker (1981) described the mafic plugs as coarse grained and diabasic with 45 percent euhedral
Tv
Basalt of Hubbs Creek
Eocene and Paleocene(?)
Mafic basalt, layered tuff, tuff breccia and breccia
Tov
Orca Group -- volcanic rocks, undivided
Tholeiitic pillow basalt, pillow breccia, and minor aquagene tuff.  Thin sequences of dark-gray argillite and siltstone are interbedded with the volcanic rocks and locally compressed between pillows.  Volcanic rocks are exclusively of oceanic tholeiite a
Orca Group -- Volcanic rocks, undivided
Thick and thin tabular bodies of altered tholeiitic basalt consist chiefly of variably pillowed, massive, or crudely columnar flows, but also include pillow breccia, aquagene tuff, and diabase or gabbro sills. Minor mudstone and siltstone that are interb
Orca Group:  Volcanic rocks, undivided
Thick and thin tabular bodies of altered tholeiitic basalt. Pillowed, massive or crudely columnar flows; pillow breccia, aquagene tuff, and diabase or gabbro sills. Local interbedding of mudstone and siltstone. Metamorphosed to zeolite or prehnite-pumpel
Mostly tabular or lenticular bodies of mafic volcanic rocks altered to greenstone and not examined in detail.  As mapped, may include pillowed or massive flows, broken pillow breccia, tuff, and dikes.
Top
Orca Group:  Pillow basalt
ORCA GROUP:  Pillow breccia and massive flows are subordinate in quantity to pillow basalt.  Minor intercalated sedimentary rocks are predominantly siliceous mudstone and argillite.  Interpillow material consists of silicious mudstone, sandstone, or carb
ORCA GROUP:  Mostly tabular or lenticular bodies of mafic volcanic rocks altered to greenstone and not examined in detail.  As mapped, may include pillowed or massive flows, broken pillow breccia, tuff, and dikes.
Pillow breccia and massive flows are subordinate in quantity to pillow basalt.  Minor intercalated sedimentary rocks are predominantly siliceous mudstone and argillite.  Interpillow material consists of silicious mudstone, sandstone, or carbonate rocks.
Orca Group:  Pillow basalt and sedimentary rocks
Pillow basalt, massive basalt flows, minor volcanic breccia interbedded with sandstone, siltstone, and shale.  Distinguished from the interbedded sedimentary and mafic volcanics rocks unit on the basis of the predominance of pillow basalt in the section.
Tgb
Layered gabbro and cumulate ultramafic rocks in Fairweather Range
Layered gabbro and cumulate ultramafic rocks in Fairweather Range -- not on map
Tdqd
Quartz diorite
Medium-grained, subhedral granular quartz diorite containing plagioclase, quartz orthoclase, chinopyroxene, and minor hornblende and biotite.  Locally highly altered.  Probably mostly subvolcanic and a variant of the diorite intrusive unit (Tdd)
Tdd
Diorite
Medium-grained, subhedral granular diorite consisting of subhedral plagioclase, clinopyroxene generally altered to actinolite, and locally minor hornblende and biotite
Porphyry
Light-gray to gray hornblende-plagioclase dacite porphyry
Granodiorite
Nonfoliate, fine- to medium-grained hypidiomorphic granular rocks of granodiorite, and subordinate granite, and local dioritic or gabbroic border zones
K-Ar on biotite and hornblende of 8.4+0.25 m.y.
Ti
Elongate plutons, emplaced in Valdez Group, of medium-grained, hypidiomorphic-granular granodiorite and tonalite, late-stage dikes and sills of dacite.  Assumed to be partial melt of flysch of Valdez Group.  Similar rocks in Bering Quad.  A dacite phase
K-Ar (from Anchorage quad) of 33.9+2 m.y.
Miocene and Oligocene
Dominantly fine- to medium-grained, equigranular to seriate hypidiomorphic muscovite-biotite and biotite granodiorite and related rocks in 10 small, widely distributed bodies cut diverse older plutonic and metamorphic rocks
K-Ar ages on mica yielded 20.9, 24.1, and 30.6 Ma; dates on possibly related dikes were 25.3 and 23.5 Ma.
Ti?
Granodiorite and granite
Chiefly light gray, fine- to coarse-grained, hypabyssal, muscovite-biotite granodiorite and granite that occur in four moderate-size stocks that chiefly intrude the Yakutat group
K-Ar dates of 46.8 to 51.1 Ma
Mount Sanit Elias
Ti3
Tonalite
Mostly biotite tonalite but also includes biotite-muscovite +/- garnet tonalite and trondhjemite.  Includes both weakly foliated, syn-D plutons (Ti3a) and unfoliated, post D plutons (Ti3b)
Ti2
Mostly hornblende-biotite tonalite but also includes biotite tonalite.  Strongly foliated and lineated plutons with fabrics subparallel to D2 in adjacent metamorphic rocks
Metamorphic
Ti3b
Mostly biotite tonalite, but also some biotite-muscovite +/- garnet trondhjemite and granodiorite.  Unfoliated plutonic rocks
Ti3a
Mostly biotite tonalite, weakly foliated, syn-D plutons
Only includes mafic plugs in the eastern Cordova quadrangle west of Nichawak Mountain mainly in the Blying Sound quadrangle.  Miller (1975) and Winkler and Plafker (1981) described the mafic plugs as coarse grained and diabasic with 45 percent euhedral p
Tgg
Granite and granodiorite
Generally medium- and medium- to coarse-grained hypidiomorphic-granular biotite granite with border phases of biotite + or - hornblende granite to granodiorite and tonalite.  Plutons of this unit are generally medium- and medium- to coarse-grained hypidi
Six K/Ar ages on hornblende, biotite, and phlogopite ranging from 50.5 to 53.5 Ma
Tertiary? (Eocene?)
Two small discordant stocks of biotite-hornblende granite and granodiorite.  Unfoliated, fine- to medium-grained hypiomorphic granular rocks.  Equal proportions granite and granodiorite.
Granite, granodiorite, and diorite -- Chugach terrane
Chiefly light gray, fine- to medium-grained, hypabyssal, biotite and biotite-muscovite granite, granodiorite, and diorite that occur in small- to medium-size stocks that chiefly intrude the Valdez Group of the Chugach terrane
Tonalite and granodiorite -- Wrangellia and Alexander terranes
Small fine- to medium-grained, light-colored tonalite and granodiorite stocks, sills and dikes, only a few of which have been delineated on the map.  The dikes consist manly of fine- to medium-grained biotite granite and lesser granodiorite and range in
Granitoid rocks
Granitoid rocks-- Biotite and biotite-hornblende granodiorite, granite, and minor tonalite; generally medium grained, hypidiomorphic, and equigranular; foliated in many places, especially near contacts with country rocks.
K-Ar ages from 50.5 to 53.5 Ma
Chiefly light gray, fine- to coarse-grained, hypabyssal, muscovite-biotite granodiorite and granite that occur in four moderate-size stocks that chiefly intrude the Yakutat Group
Tgt
Granite and tonalite (Granite)
Consists of Alsek River pluton of strongly foliate, medium-grained, equigranular, hypidiomorphic muscovite-biotite granite and the Novatak Glacier pluton of foliate, fine- to medium-grained, equigranular to seriate, hypidiomorphic hornblende-biotite tona
Alsek River pluton has yielded a middle Tertiary K-Ar date, hornblende from the Novatak glacier pluton gave a 61 Ma K-Ar age.
Tfd
Felsic dikes
Leucocratic dikes, sills, and small stocks that are not obviously connected to large intrusive bodies are found throughout the Valdez Group flysch and locally in Orca Group flysch.  They are usually prophyyritic with fine- to medium-grained phenocrysts o
Five K/Ar dates (three whole rock and two muscovite) ranging from 43.6 + or - 1.6 to 54.8 + or - 2.7 Ma.
Tqd
Foliate, fine- to medium-grained, seriate, hypidiomorphic, biotite-hornblende quartz diorite on south face of Mount Saint Elias.
Altered biotite and hornblende tonalite
Small, sericitized hornblende-biotite tonalite plugs.  Rocks are fine- to medium-grained sericitized tonalite with minor quartz diorite and granodiorite.  In most sample, muscovite replaces biotite or has formed from alteration of plagioclase.
K-Ar hornblende 46.6 +/- 1.4 and muscovite of 52.4 +/- 2.6 Ma
Tsq
Snag Creek Pluton
Medium- to coarse-grained leucocratic biotite quartz monzonite
K-Ar dates give minimum age of about 50 m.y.
Granite and tonalite (Tonalite)
Tmu
Mafic and ultramafic plutonic rocks
Eocene and Paleocene?
Mafic and ultramafic plutonic rocks-- Compositionally and texturally variable unit consists mainly of medium grained gabbro, local diabase, hornblende gabbro, peridotite, and orthopyroxenite. Gabbro is slightly to moderately foliated except near contacts
Tc
Cottonwood Creek Complex
Banded granite and quartz diorite gneiss and biotite- and augite-bearing amphibolite gradational into biotite metagranodiorite and metagranite.  Weakly metamorphosed (greenschist facies).
K-Ar of metamorphic biotite and amphibole of 17 to 20 m.y.
d
Dikes
Tertiary or Cretaceous
Dikes of hornblende-feldspar porphyry, probably andesite to dacite in composition.
TKp
Older Porphyry
Baultoff Creek region is highly altered chlorite, carbonate mineral, and zoisite matrix with plagioclase phenocrysts.  Chisana region is an andesite porphyry with plagioclase phenocrysts.  May be a hypabyssal equivalent to the Chisana Formation
TKg
Felsic granitic rocks
Tertiary and Cretaceous
Graphic granodiorite
Hornblende granodiorite with graphic quartz and potassium feldspar
TKd
Diorite (undifferentiated)
Porphyritic to eqyigranular granitic intrusives that are predominantly augite-hornblende  diorite, equigranular hornblende diorite, augite-olivine syenodiorite, and augite bearing norite
TKm
Orca Group -- melange
Consists of extensive serpentinized ultramafic rocks including dike-like bodies of rodingite, as well as blocks of layered gabbro, crossite schist, pillow basalt, marble, chert of probable Late Triassic or Early Jurassic age, and diverse metamorphosed an
Tectonite
Ku
Predominantly Upper Cretaceous sedimentary rocks
Cretaceous
Parts of the Matanuska-Wrangell terrane; locally subdivided into Moonshine Creek Formation: siltstone and sandstone, with minor conglomerate;  Schulze Formation: porcellanite, with minor sandstone and conglomerate;  Chititu Formation: mudstone and shale,
'Abundant fossils' indicate an age span from late Albian to Maestrichtian
Ks
Continental sedimentary rocks
Late Cretaceous
Conglomerate, coarse- to fine-grained sandstone, siltstone, mudstone, and subordinate shale
Petrified wood; well preserved leaves and plants
TKs
Predominantly conglomerate, grit, and coarse sandstone.  Conglomerate ranges from clast-supported massive beds to bedded conglomerate sandstone.  Clasts (up to 20 cm) rounded to subrounded crystalline rock, gneiss, gray chert, greenstone, and quartz (Cre
fragments of lignitized wood (up to 30 cm long) locally abundant
Kun
Nonmarine sedimentary rocks - Wrangellia Terrane
Conglomerate, sandstone, siltstone, and mudstone
Locally contains abundant fossils
Kmu
Matanuska Formation -- upper part
Late Cretaceous -- mid-Coniacian to Maestrichtian
A very thick sequence of marine siltstone, claystone, and sandstone in interbedded with lenticular and channelized deposits of sandstone and conglomerate.  Contact with lower part of unit presumed to an unconformity.  Deposition thought to occur on the f
Kml
Matanuska Formation -- lower part
Cretaceous -- late-early-Albian, Cenomanian, Turonian, and early Coniacian
Marine siltstone, shale, sandstone, and pebbly sandstone are interbedded with subordinate silicieous, foraminiferal shale and fine-grained zeolitized sandstone.  Contact with upper part of unit (unit Kmu) presumed to be an unconformity and is angular unc
Kl
Lower Cretaceous sedimentary rocks
Early Cretaceous
Parts of the Matanuska-Wrangell terrane; locally subdivided into unnamed Neocomian rocks:  sandstone, shale, and impure bioclastic limestone with Inoceramus;  (Albian) Kennecott Formation:  sandstone, siltstone, minor basal and intraformational conglomer
Neocomian rocks:  Inoceramus and other fossils that indicate Hauterivian and barremian;  Kennecott Formation:  Moffitites robustus, and Brewericeras hulenense
Km
Matanuska Formation
Principally shallow marine and/or terrestrial in origin. The shallow marine rocks consist of thin-bedded  brownish-weathering light-gray shaly siltstone and gray mudstone which interbeds with quartz-rich arkosic sandstone, grit and conglomerate.  Locally
Ammonites, Brewericeras hulenense and Puzosia alaskana of late early Albian age were found in the shallow marine rocks.  Fragments of lignitized wood is very abundant in the shallow marine and/or terrestrial rocks
Kk
Kennicott Formation
Early Cretaceous, Albian
Dominantly sandstone (fine-grained feldspathic graywacke and arkosic wacke) and siltstone, but includes shale and some conglomerate, whose clasts are predominantly Nikolai Greenstone, at the base.  Generally dark greenish gray and weathers to brown; is t
The pelecypods of the genus Aucellina represents the older of the two Albian faunal zones
Kkp
Kuskulana Pass Formation
Early Cretaceous, Neocomian, Barremian and Hauterivian
Thin bedded sandstone (very fine grained, dark greenish gray, arkosic-subordinate calcareous arkosic-lithic wacke), siltstone, and subordinate shale.  Limy lenses and small spheroidal concretions are sparsely distributed.  Locally cut by Tertiary hypabys
Meager ammonite and pelecypod fauna indicate Hauterivian and Barremian Stages of the Early Cretaceous; more definitive ammonite from C-7 document the Barremian Stage
Kb
Berg Creek Formation
Marine clastic rocks consisting of calcareous conglomerate, conglomeratic sandstone and siltstone, and calcarenite.  Basal strata generally are pebble, cobble, and boulder conglomerate consisting of clasts derived from nearby bedrock.
Inoceramus
Js
Unnamed Jurassic marine sedimentary rocks
Middle Jurassic (Callovian)?
Marine clastic rocks consisting mostly of sandstone, siltstone, and mudstone, which contain many interbeds of pebble- and cobble-conglomerate.  Greenish-gray sandstone predominates in lower part of the sequence, in many places it is calcareous and cross-
Unnamed Callovian fossils
Clastic sedimentary rocks
Dark greenish-gray to very dark gray shale, locally concretionary, with subordinate siltstone, arkosic sandstone, and arkosic granule- to pebble conglomerate. Chocolate-brown to reddish-brown weathering colors and hackly to slaty cleavage are conspicuous
Contains sparse but diverse megafauna of probable Neocomian age
Marine sedimentary rocks
Wrangellia terrane.  Consists of Berg Creek Formation and unnamed marine sedimentary rock
Kbc
Medium bedded with occasionaly cross-bedding, rocks consist of limestone (well sorted, light gray, impure bioclastic sandy grainstone) and subordinate verigated green-gray-brown pebble basal conglomerate.  The formation probably formed in near-shore envi
Abundant and dominant Inocerimus as well as Pinna, Simbirskites, and belemnites.  Fossils indicate the Hautervian and Barremian Stages of the Early Cretaceous
Bernard Creek terrane, deleted, now McHugh Complex
mid-Cretaceous?
Mylonitic greenschist.  Relict bedding and volcaniclastic textures are retained locally.  Elsewhere unit is nearly massive, but cataclasis and neomineralization generally are so pervasive that they obliterate any primary features.
VA005
KJm
McHugh Complex
Early Cretaceous and Jurassic?
Pervasively deformed assemblage of diverse lithologies (melange).  Lithologies include gabbro, greenstone, marble, wacke, and diverse plutonic and metamorphic rocks including blueschist.  Rocks occur in three discrete belts, the northernmost which yields
Radiolaria from chert ranges from Triassic to mid-Cretaceous (Albian or Cenomanian).
Mzm
Early(?) Cretaceous to Late Jurassic
A structurally chaotic melange-like unit of accreted oceanic rocks that crops out in a narrow belt to about 1.5 km wide. The complex consists of pervasively disrupted broken formation that originally was mainly tholeiitic pillowed basalt and related frag
Mzpg
Phyllite/greenstone melange
Structurally chaotic melange-like unit of dominantly massive medium- to dark-green metabasalt interbedded with gray to black metapelitic rocks and intercalated minor gray to white metachert; occurs structurally between the McHugh Complex and Valdez Group
Kc
Chisana Formation
Thin- to medium-bedded andesite flows and diverse volcanoclastic rocks. Probably represents Klein Creek and related mid-Cretaceous plutons of Nabesna Quad. Widespread in Nabesna Quad.
Subaqueous and subaerial volcanic and volcaniclastic rocks; Upper Part: primarily andesite, basaltic andesite flows, fragmental volcanic rocks, suordinate porphyritic andesite, thin-bedded  conglomerate, grit, sandstone, and tuff.  Lower Part: fragmental
Lignitized wood; Inoceramus; Shasticrioceras
Lower Cretaceous
Volcanic flows, massive volcanic breccias, and minor interbedded volcaniclastic rocks.  Dominantly andesites and basaltic andesites, generally containing conspicuous augite phenocrysts
Andesite flows, fragmental volcanic rocks, and volcaniclastic rocks locally strongly propylitized
Kvu
Valdez Group:  Ultramafic rocks
VALDEZ GROUP:  Serpentinized peridotite and dunite occur at three localities underlain by the Valdez Group:  two of these are on the Resurrection Peninsula and the third is near the head of Port Fidalgo.  On the Resurrection Peninsula small sparse inclus
Kug
Undifferentiated Plutonic rocks
Cretaceous (?)
Porphoritic medium-grained biotite-hornblende granodiorite, coarse-grained ophitic gabbro, and medium-grained, weakly foliated biotite-rich granodiorite-diorite
Kgq
Gardiner Creek Pluton
Part of the Middle Cretacous plutonic event.  Rocks are mainly foliated quartz monzonite.  Also coarse-grained leucocratic biotite quartz monzonite
K-Ar dates indicate emplacement of 89 to 94 m.y.
Kcg
Cheslina Pluton
Part of the Middle Cretacous plutonic event.  Rocks are mainly foliated quartz monzonite.  Also medium-grained biotite-hornblende granodiorite with hornblende monzonite
Ktq
Tok-Tetlin Pluton (Tetlin phase)
Porphhyritic biotite-hornblende quartz monzonite locally gradational to biotite-hornblende granodiorite
K-Ar dates indicate emplacement of 92 to 94 m.y.
Kmg
Tok-Tetlin Pluton (Mineral Cairn phase)
Porphyritic biotite-hornblende granodiorite and quartz monzonite with minor biotite diorite
Ktg
Tok-Tetlin Pluton (Tok phase)
Fine- to medium-grained biotite-hornblende granodiorite
Ktm
Tok-Tetlin Pluton, Mineral Cairn phase
Mineral Cairn phase.  Chiefly granodiorite but gradational into diorite and quartz monzonite.  Rocks are weakly to strongly foliated.
K-Ar dates indicate an emplacement age of 92-94 m.y. (Richter and others, 1975)
Ktt
Tok-Tetlin Pluton,Tetlin phase.
Tetlin phase.  Poyphyritic quartz monzonite with abundant and conspicuous orthoclase phenocrysts in a medium- to coarse-grained hypidiomorphic-granular matrix of plagioclase, quartz, biotite, and hornblende.  Rocks are non-foliated.
Kg
Altered tonalite
Fine- to medium-grained, equigranular to seriate, hypidiomorphic and foliate hornblende-biotite tonalite.  Mafic grains are oriented; most samples are pervasively sheared and altered along fractures.  Intrude Yakutat Group melange facies.
K-Ar age reported on something related to pluton at 100 Ma (report unclear)
Kum
Ultramafic rocks
Serpentinite, serpentinized periodotite, and dunite, with subordinate clinopyroxenite
Serpentinized peridotite and dunite occur at three localities underlain by the Valdez Group:  two of these are on the Resurrection Peninsula and the third is near the head of Port Fidalgo.  On the Resurrection Peninsula small sparse inclusions of altered
Kkg
Klein Creek Pluton
Medium grained, hypidiomorphic granular, unfoliated hornblende-biotite granodiorite and quartz monzonite.  Coextensive with, or satellites of, the Klein Creek intrusive of Nabesna Quad.
Nabesna Quad date of 111+3 m.y.
Ksg
Slana Pluton
Part of a Middle Cretaceous plutonic event.  Equigranular hornblende granodiorite.  Locally weakly foliated
Kas
Antler Creek Pluton
Part of a Middle Cretaceous plutonic event.  Equigranular hornblende syenodiorite.  Weakly foliated
K-Ar data yields ages between 105 and 117 m.y.
Kah
Border of Antler Creek Pluton
Part of a Middle Cretaceous plutonic event.  Coarse-grained hornblendite
Part of a Middle Cretaceous plutonic event.  Equigranular hornblende-biotite granodiorite and quartz monzonite with minor hornblende syenodiorite, biotite gabbro, and hornblende diorite
Kng
Nabesna Pluton
Part of a Middle Cretaceous plutonic event.  Equigranular hornblende-biotite granodiorite with quartz diorite, diorite, and trondhjemite.  Propylitic and argillic alteration common
Granodiorite pluton
Granodiorite pluton, Wrangellia terrane
Klein Creek pluton
Hornblende-biotite granodiorite and quartz monzonite.
K-Ar ages indicate emplacement age of 105-117 Ma
Medium grained biotite-hornblende granodiorite with hypidiomorphic-granular texture; locally weakly to strongly foliated
K-Ar date indicates age of 125 +/- 4 my
Granodiorite and quartz diorite
Fine to medium-grained, subhedral, granular rocks containing hornblende, plagioclase, and quartz, with minor biotite, augite, and potassium feldspar.  Chloritization and saussuritization common.  Host marine sedimentary rocks (KJs), limestone (Trtl, Trml
Knp
Quartz-feldspar porphyry
Part of a Middle Cretaceous plutonic event.  Equigranular, quartz-feldspar, porphyry with altered plagioclase
Kbd
Buck Creek Pluton
Part of a Middle Cretaceous plutonic event.  Equigranular hornblende quartz diorite and syenodiorite, and subordinate leucocratic hornblende granodiorite.  Locally strongly foliated
Ksd
Suslota Pass Pluton
Part of a Middle Cretaceous plutonic event.  Equigranular hornblende diorite
Kdd
Devils Mountain Pluton
Part of a Middle Cretaceous plutonic event.  Equigranular hornblende diorite, quartz diorite, and hornblende granodiorite.  Strongly porpytically altered.
Kcs
Chisana Pluton
Part of a Middle Cretaceous plutonic event.  Equigranular clinopyroxene diorite, clinopyroxene syenodiorite, and clinopyroxene-hornblende monzonite
Kkd
Hornblende-rich diorite
Part of a Middle Cretaceous plutonic event.  Equigranular hornblende-rich diorite
Kd
Horneblende Diorite
Small stocks, chiefly of hornblende diorite.  Hornblende largely altered to chlorite.
Undifferentiated Granitic Rocks
middle Cretaceous
Chiefly altered quartz diorite and granodiorite
Knt
Trondhjemite
Part of a Middle Cretaceous plutonic event.  Medium- to coarse-grained leucocratic trondhjemite with sodic plagioclase, quartz, and biotite
KTj
Tertiary or middle Cretaceous
White (C.I. 0-5), fine-to medium grained, small trondhjemite stoks and associated dikes consisting of plagioclase and -quartz with sparse biotite and white mica in the southeastern part of the D-2 quadrangle
Kfc
Fox Creek terrane  Unit deleted on new VA map
Intercalcated lower greenschist and transistional blueschist facies metasedimentary and mafic metavolcanic rocks.  Over broad areas the rocks have a cataclastic fabric, locally relict primary sedimentary and volcaniclastic textures are retained.  Unit is
Khc
Haley Creek terrane
Metamorphosed complexly deformed and tectonically mixed plutonic and sedimentary rocks.  Metaplutonic rocks are most abundant in southern part of the terrane and are compositionally diverse and weakly to strongly foliated.  Although diorite and granodior
Kvs
Valdez Group -- Metasedimentary rocks, undivided
Weakly to strongly foliated marine argillite, siltstone, sandstone, and conglomeratic sandstone.  Lower greenschist facies metamorphism.  Probable volcanic source terrane.
Maestrichtian pelecypods collected outside of Valdez quadrangle.
Kvm
Valdez Group -- Phyllite and schist. Delete unit on new VA map
Low-grade metamorphosed (lower greenschist facies) pelitic rocks consisting of homogeneous phyllite and schist.  These rocks shown much stronger foliation than the undivided metasedimentary rocks (unit Kvs) of the Valdez Group.  Probable volcanic source
KJv
Valdez Group
Cretaceous and Jurassic (?)
Thin- to medium-bedded metamorphosed flysch, interlayered metagraywacke and argillite, minor schist, slate, and phyllite; metamorphosed to chlorite- or biotite-grade greenschist-facies mineral assemblages
'Metafossils' recorded by Jones and Clark (1973) yield Maestrichain age
Kv
Valdez Group -- Metaflysch
Mainly phyllitic metapelite (70-80 percent) and subordinate metagraywacke in thin to very thick beds with minor metavolcanic rocks metamorphosed mainly to lower greenschist facies. Locally hornfelsed and massive near Tertiary plutons.  The metapelite is
Valdez Group: Metasedimentary rocks, undivided
Thick sequence of rhythmically alternating, multiply-deformed, metamorphosed turbidites that consist of metasandstone, metasiltstone, argillite, slate and phyllite and rare beds of pebbly argillite. Beds generally a few centimeters to a few meters thick.
Valdez Group:  Sedimentary rocks, undivided
Thick sequences of deformed and metamorphosed flysch consisting of metasandstone, metasiltstone, argillite, slate, and phyllite, with rare beds of conglomerate and pebbly argillite.  In many places primary internal sedimentary structures, consisting of g
Pelecypod:  Inoceramus kusiroensis, Inoceramus ulrichi, and Inoceramya concentrica
K/Ar date on biotite semischist of 51.5 + or - 1.5 Ma
Valdex Group:  Sedimentary rocks, undivided
VALDEZ GROUP:  Thick sequences of deformed and metamorphosed flysch consisting of metasandstone, metasiltstone, argillite, slate, and phyllite, with rare beds of conglomerate and pebbly argillite.  In many places primary internal sedimentary structures,
Kvvm
Valdez Group -- Interbedded metavolcanic and metasedimentary rocks-
Approximately equal amounts of interbedded metavolcanic and metasedimentary rocks. Metavolcanic rocks are chiefly semischistose metatuff and breccia, including local probable pillow lava.  Metasedimentary rocks chiefly slate and phyllite, although metasi
Kvvs
Valdez Group: Interbedded metavolcanic and metasedimentary rocks
Equal proportions of interbedded metavolcanic and metasedimentary rocks. Metavolcanic--semischistose metatuff and breccia and minor pillow basalt. Metasedimentary--slate, phyllite, with metasilstone and metasandstone interbedding. Variable metamorphic gr
Valdez Group:  Interbedded volcanic and sedimentary rocks
This unit is composed of approximately equal amounts of interbedded volcanic rocks, consisting of volcanic breccia, tuff, tuffaceous sediment, and minor pillow basalt, and sedimentary rocks, consisting of sandstone, siltstone, shale, and chert.  The two
K-Ar date on amphibote-bearing greenschist of 47.6 +/- 1.4 Ma
VALDEZ GROUP:  This unit is composed of approximately equal amounts of interbedded volcanic rocks, consisting of volcanic breccia, tuff, tuffaceous sediment, and minor pillow basalt, and sedimentary rocks, consisting of sandstone, siltstone, shale, and c
K-Ar date on amphibote-bearing greenschist of 47.6 + or - 1.4 Ma
Kvv
Valdez Group -- Metavolcanic rocks, undivided
Mafic metatuff and minor massive or weakly foliated greenstone having rarely preserved vague pillow shapes.  Lower greenschist facies metamorphism.  Most of these metavolcanic rocks are schistose and the metavolcanic are often the loci of intense deforma
K-Ar whole-rock age on metatuff of 53.5 +/- 1.6 Ma is thought to date matamorphism.
Valdez Group: Metavolcanic rocks, undivided
Tholeiitic metabasalt and basaltic metatuff, including local pillow lava, pillow brecia, and gabbroic dikes and sills. Metabasalt form rugged, nearly massive outcrops, whereas semischistose metatuff forms more subdued outcrops. Variable metamorphic grade
Kvgr
Valdez Group:  Greenstone
This unit consists of massive greenstone, metamorphosed pillow basalt, and mafic dikes exposed near the heads of Woodworth and Schwan Glaciers.  Elsewhere in the Cordova and Valdez quadrangles, the unit includes lenticular bodies of chorite schist that m
VALDEZ GROUP:  This unit consists of massive greenstone, metamorphosed pillow basalt, and mafic dikes exposed near the heads of Woodworth and Schwan Glaciers.  Elsewhere in the Cordova and Valdez quadrangles, the unit includes lenticular bodies of chorit
Valdez Group -- Amphibolite schist
Late(?) Cretaceous
Mostly massive, black to greenish-black fine- to medium-grained amphibolite schist  Probably derived from massive basalt and gabbro.  Coded as 2710 on WRST map
Valdez Group -- Schistose metaflysch
Medium to medium-light gray, very fine- to medium-grained schistose metapelite, metagraywacke, and minor metatuff. Commonly weathers to blocky or tabular fragments and form banded gray outcrops streaked with iron-oxide stains.
Valdez Group: Schist
Homogenous pelitic schist and minor amphibolite; includes spotted biotite-plagioclase-quartz schist. Common banding probably represents original layering. Transitional into gneissose rocks to the east and into greenschist-facies rocks of metasedimentary
Mostly massive, black to greenish-black fine- to medium-grained amphibolite schist  Probably derived from massive basalt and gabbro.
Kvm?
Schist of Mount Augusta -- Amphibolite schist
Cretaceous(?)
Dark-greenish black, fine-grained, partially segregated amphibolite schist
Ksm
Valdez Group -- Pelitic and quartzofeldspathic schist and gneiss
Reddish weathering, varibly banded, strongly schistose to granoblastic pelitic and quartzofeldspathic schist and gneiss.  Typically a garnetiferous graphitic schist.  Sedimentary clastic protolith.
Valdez Group, amphibolite-facies flysch
Dominantly schist.  Flysch metamorphosed to lower greenschist facies
Kvg
Valdez Group -- Schistose to gneissic metaflysch and migmatite
Amphibolite-facies schist, banded gneiss, and migmatitic gneiss.  Fine- to coarse-grained but mostly medium- to coarse-grained.  Gray to light gray, and characteristically weathers rusty brown. Layering is irregular and inhomogeneous with discontinuous q
ap
SCHIST OF MOUNT AUGUSTA -- Pelitic schist
Reddish-weathering, quartzofeldspathic pelitic schist; characteristic assemblages consist of plagioclase (An 15), biotite, and quartz with accessory magnetite and sulfides.  Locally contains porphyroblasts of euhedral garnet and poikilitic staurolite.  O
K-Ar dating of a biotite and hornblende pair in the adjacent Saint Elias quadrangle yields recrystallization ages of 17-23 m.y.
av
SCHIST OF MOUNT AUGUSTA -- Amphibolite schist
Cretaceous(?) and Jurassic(?)
Dark-greenish black, fine-grained, partially segregated, amphibolite schist having assemblages of hornblende and plagioclase (An > 15) with minor quartz, magnetite, and sphene.  Probably mainly derived from mafic basaltic flow rocks.  Occurs in a large f
avp
SCHIST OF MOUNT AUGUSTA -- Intercalated quartzofeldspathic schist and amphibolite
Intercalated quartzofeldspathic schist and amphibolite.  Large fault-bounded block of metavolcanic and metasedimentary rocks metamorphosed to dominantly epidote-amphibolite facies assemblages that are in part doubly foliated.  Inferred to be correlative
Valdez Group: Gneiss
Muscovite-biotite-quartz-plagioclase (+/- sillimanite and garnet) schist, banded gneiss, and migmatitic gneiss; many local intrusive stringers, dikes, and sills of granodiorite and granite. Transitional into schistose rocks to the north, south, and west.
Valdez Group:  Paragneiss
Predominantly metasedimentary rocks with well-developed gneissic foliation consisting of alternating quartz and feldspar-rich layers with biotite-rich layers.  The paragneiss is brown weathering, medium grained, and banded on a 2 to 4 mm scale.  However,
VALDEZ GROUP:  Predominantly metasedimentary rocks with well-developed gneissic foliation consisting of alternating quartz and feldspar-rich layers with biotite-rich layers.  The paragneiss is brown weathering, medium grained, and banded on a 2 to 4 mm s
Kvg/Tg
Valdez Group -- Schistose to gneissic metaflysch and migmatite and stockwork of dikes?
Kvsm
Valdez Group -- Undifferentiated metavolcanic and metasedimentary rocks
Largely interbedded mafic to intermediate metavolcanic rocks that were mainly volcaniclastic and metaclastic.  Metasedimentary sequence locally includes metachert and thin lenses of marble.
Kvsm?
Schist of Mount Augusta -- Interbedded quartzofeldspathic schist and amphibolite
Reddish weathering doubly foliated quartzofeldspathic schist interbedded with amphibolite schist
Ksm?
Kpm
Pelitic and quartzofeldspathic schist and gneiss
Pelitic and quartzofeldspathic schist and gneiss with abundant sills, dikes, and small intrusive bodies of felsic granitic rocks
green
Schist
Cretaceous ?
Upper greenschist to amphibolite facies schist derived from metamorphism of interbedded graywacke and argillite of the Valdez Group
pink
Transitional gneiss
Age not given
Upper amphibolite facies schist and gneiss interlayered at scale of meters to centimeters.  Top of unit marked by appearance of quartofeldspathic segregations in metapelite and base of unit marked by loss of stratal continuity through development of gnei
gray
Gneiss
Gray, banded quartzofeldspathic gneiss
orange
Orthogneiss
Metamorphosed plutonic rocks.  Mostly Ti2 plutons within the gneissic core of the complex
KJs
Cretaceous and Jurassic
Thin- to medium-bedded argillite and graywacke, metamorphosed to hornfels near Klein Creek pluton.  Part of informally designated Nutzotin Mountains sequence.
Buchia pelecypod, indicating Late Jurassic age
Early Cretaceous and Late Jurassic
Upper Part: Argillite, graywacke, and mudstones, capped by sandstone, siltstone, and shale.  Middle (major) Part: Argillite, siltstone, and graywacke, that alternate with a pebble to cobble conglomerate, pebbly graywacke, and an argillite.  Lower Part: A
Buchia indicate Late Jurassic and Early Cretaceous age
Thin- to medium-bedded argillite and graywacke.  Graywacke is typically graded and rhythmically bedded.  Metamorphosed to hornfels near Klein Creek pluton.  Part of the informal Nutzotin Mountains sequence
Graded sedimentary rocks and conglomerate.  Argillite grading to stiltstone to graywacke with interbedded massive, fine- to coarse-grained graywacke, and pebble and boulder conglomerate.  Locally known as the Nutzotin Mountains Sequence.
Ja
Argillite
Late Jurassic
Dark shaly argillite in poorly defined beds with abundant thin beds and lenses of dense dark-gray iron-carbonate-bearing mudstone and siltstone.  Minor interbeds of gray calcareous siltstone and sandstone.
Nutzotin Mountain Sequence
Lower Cretacous and Upper Jurassic
Marine assemblage of dark argillite, gray siltstone, and graded beds of argillite-siltstone-graywacke.  Contact metamorphism with the quartz diorite (Kg) has resulted in a banded calc-silicate hornfels
Sparse Buchia indicate a late Mesozoic age
TKc
Conglomerate and sandstone
Green-gray to brown-gray pebble-to-boulder conglomerate, conglomeritic sandstone, and coarse-grained sandstone
Kys
Yakutat Group -- flysch facies
Cretaceous and Jurassic(?)
Yakutat Group is a heterogeneous assemblage including clastic sedimentary rocks, altered volcanic rocks, chert, carbonate, and granitic rocks.  Two major subdivisions that are commonly structurally juxtaposed, a flysch facies and a melange facies.  Flysc
Kys?
Yakutat Group -- flysch facies(?)
Yakutat Group is a heterogeneous assemblage including clastic sedimentary rocks, altered volcanic rocks, chert, carbonate, and granitic rocks.  Two major subdivisions that are commonly structurally juxtaposed, a flysch facies and a melange facies.  This
Contains very sparse warm water molluscan fauna and abundant carbonized sub-tropical plant remains.
Kgd
Granodiorite -- Wrangellia Terrane
hbqd
Hornblende-biotite quartz diorite; Peninsular Terrane
Jurassic or Cretaceous
Hornblende-biotite quartz diorite
hbqm
Hornblende-biotite quartz monzonite; Peninsular Terrane
Hornblende-biotite quartz monzonite
hbgd
Hornblende-biotite granodiorite; Peninsular Terrane
Hornblende-biotite granodiorite
Kyx
Yakutat Group -- melange facies
Yakutat Group is a heterogeneous assemblage including clastic sedimentary rocks, altered volcanic rocks, chert, carbonate, and granitic rocks.  Two major subdivisions that are commonly structurally juxtaposed, a flysch facies and a melange facies.  Melan
s
Sandstone
Larger lenticular bodies to 300m thick of massive laumonite-rich lithofeldspathic to feldspatholitihic sandstone mainly within the flysch facies.  Probably represent deep sea channel fills with andesitic volcanic detritus dominant in the lithic component
c
Larger lenses and beds of well rounded and sorted pebble and cobble conglomerate to 200m thick that are locally developed within both the flysch and melange facies.  Includes abundant angular blocks of gray oolitic limestone containing chert nodules in K
g
Greenstone
Larger greenstone masses within the melange facies of the Yakutat Group, generally massive and structureless but locally with faint pillow forms and agglomeratic texture.  Commonly with epidote-rich pods and stringers and cut by diorite dikes.  Associate
Jurassic
Large bodies of foliate, fine- to medium-grained hornblende biotite tonalite associated with meta-greenstones.  Interpreted as allochthonous blocks in the melange.
K-Ar ages ranging from 146-178 m.y.
Kyb
Metamorphic rocks of the Brabazon Range
Mainly amphibolite facies rocks more than 1,000 -m-thick.  Grades over narrow interval into zeolite- and prehnite-pumpellyite-grade rocks of the Yakutat Group.  Protolith mainly graywacke-carbonaceous pelite sequence recrystallized to quartzofeldspathic
Kym
Schist of Nunatak Fiord -- schist
Creatceous(?)
Typically fine- to medium-grained, semigranoblastic quartzofeldspathic schist.
Kyn
Schist of Nunatak Fiord -- Amphibolite-diorite complex at the Nunatak
High-grade amphibolite-diorite complex characterized by segregation and injection gneisses.  Probable metamorphosed equivalent of Yakutat Group flysch facies.
Discordant K-Ar biotite-hornblende pair yielded 30 and 47 Ma, respectively.
Kyvm
Schist of Nunatak Fiord -- Metavolcanic rocks of Novatak Glacier area
Predominantly massive porphyritic mafic flow rocks interbedded with thinly laminated green to light-gray metatuff.  Metamorphosed to fine-grained, schistose, partly segregated epidote-amphibolite and amphibolite-facies assemblages.
Kyxm
Schist of Nunatak Fiord -- Schist of Novatak Glacier area
Lithologically diverse sequence of metasediementary and metavolcanic rocks.  Mainly thin-bedded metapelite, tuffaceous metapelite, pelitic schist, and quartzofeldspathic schist with subordinate stretched pebble conglomerate, metachert, gray-weathering ma
K-Ar recrystallization age of 65 Ma
Undivided Jurassic marine sedimentary rocks
Lower parts of the Matanuska-Wrangell terrane; subdivided into Lubbe Creek Formation: spiculite and minor coquina; Nizina Mountain Formation: graywacke; Root Glacier Formation: mudstone, siltstone, and subordinate sandstone, shale, and conglomerate.  Bro
'Abundant fossils' indicate an age span from Pliensbachian to Kimmeridgian
Jk
Kotsina Conglomerate
Middle or Late Jurassic?
Well-indurated massive to very thick-bedded cobble- and pebble-conglomerate, with some bouldery strata.  Olive-gray lithic and feldspathic sandstone, siltstone, and carbonaceous shale are interbedded in many places and increase in proportion west of Long
Plant scraps
K-Ar age on biotite from a clast of 161 Ma and on hornblende from cross-cutting dike of 145 Ma
Late and Middle Jurassic
Thin- to thick-bedded conglomerate with locally derived pebbles and cobbles and subordinate sandstone and shale.  Extends into Valdez Quad. Correlates to rocks in Talkeetna Mtns
'Isotopic age' indicates an age span from late Jurassic to Middle to Late Jurassic
JTrc
Marine clastic and carbonate rocks, undivided
Late or Middle Jurassic to Late Triassic
Wrangellia terrane, Consists of Kotsina Conglomerate (Middle or Late Jurassic), lower part of the McCarthy Formation (Late Triassic), and the Chitistone and Nizina Limestones (Late Triassic)
Early Cretaceous and Late Jurassic, Berriasian, Thithonian, and Kimmeridgian
Forming bold, dark greenish gray, craggy outcrops, rocks consist of well-indurated massive cobble and pebble conglomerate, minor boulder conglomerate, with some arenite sandstone and siltstone interbeds.  Conglomerate clasts derived from Triassic limesto
Isotopic age determined with a conglomerate clast and cross-cutting dike from the nearby Valdez quad yielded ages of 142 +/- 5 and 157 +/- my
Jtk
Talkeetna Formation
Early Jurassic
Marine and non-marine andesitic and basaltic tuff, tuff breccia, and volcanogenic sedimentary rocks.  Small, isolated bodies of light- to dark-gray unfossiliferous saccharoidal limestone may be parts of the units in the Valdez quadrangle.
Mollusks and brachiopods
Jtrd
Rhyodacite flows; Talkeetna Formation
Rhyodacite flows with minor sandstones and lesser dacite flows
Jta
Hornblende andesite flows; Talkeetna Formation
Hornblende andesite flows
Jts
Talkeetna Formation, sandstone
Sandstone with sparse volcaniclastic rocks
Jum
Early Jurassic or older
Dunite, harzburgitic dunite, wehrlite, websterite, and clinopyroxenite comprise the Tonsina ultramafic complex.  The rocks are folded but not intensely sheared or serpentinized.
Ju
Jurassic?
Serpentized pyroxenite?  Occurs within mafic plutonic complex (unit Jmp), generally localized in strongly sheared zones.  Many areas of unit are too small to map.
Jlg
Layered quartz gabbro
Conspicously layered, hypiodiomorphic-granular textured quartz gabbro.  Layers enriched in clinopyroxene or in plagioclase and quartz give unit its prominent banded appearance.  Prehnite-pumpellyite metamorphosed, little deformed and dips quite uniformly
K-Ar age on pyroxene of 185 +/- 19 Ma is highly suspect, however matches ages on Afognak Pluton, the pluton of the Barren Islands and reputed ages on small dioritic plutons near Seldovia.
Jgr
Biotite-epidote granite
Middle Jurassic
Irregularily shaped small stocks of pink-weathering medium-grained granite.  Green biotite and granular to coarse-grained epidote are constant accessories
Jgd
Biotite-hornblende granodiorite
Irregularily shaped small stocks of pink-weathering medium-grained granite.  Green biotite is a constant accessory; hornblende and epidote are less abundant and are not present in all samples.
Granodiorite to quartz diorite
Juarssic?
Weakly foliated to foliated granodiorite to quartz diorite. Possibly equivalent to rocks of the Chitina Valley batholith Granite Range plutonic suite in the northern Chugach Mountians
Jc
Chitina Valley batholith
Weakly to strongly foliated compositionally diverse plutonic rocks.  Dominant lithology is fine-to medium-grained hypiomorphic granular quartz monzodiorite, but quartz diorite, tonalite, and granodiorite are nearly as abundant.
K-Ar hornblende ages range from 147 +/- 7 to 157 +/- 8 Ma, biotite ages are 134 and 144 +/- 7 Ma; one mineral pair is slightly discordant.
Chitina Valley Batholith
Strongly foliated Tonalite, granodiorite, and rocks rangong from granite to quartz diorite.  No known volcanic equivalents, however, coextensive with batholithic rocks of Bering Glacier Quad.  Also correlates with granitic rocks of the E Valdez Quad
Hornblende radiometric age range of 138 to 146+4 m.y.
JTrq
Hornblende quartz-diorite
Jurassic and Triassic
Part of "diorite complex."  Medium- to coarse-grained hornblende quartz-diorite, hornblende-biotite quartz diorite, and subordinate leucocratic quartz diorite
K-Ar dates of Middle Jurassic for plutonic rocks and Late Triassic for metamorphic rocks
Jt
Tonalite, diorite, and leucodiorite of Chitina Valley batholith
Tonalite, diorite, and leucodiorite of Chitina Valley batholith. Mainly diorite, leucodiorite, and tonalite, but locally includes gabbro, especially near contacts.  Generally medium-grained but varies from fine to coarse and pegmatitic.  Ranges from weak
Wrangellia terrane,  Chitina Valley batholith
Early Cretaceous and Late Jurassic, Berriasian and Thithonian
Poorly foliated, fine to medium-grained hypidiomorphic-granular granodiorite with subordinate granitic and dioritic phases.  Rocks cut locally by Tertiary hypabyssal rocks.  Sporadic vienlets consist of quartz or calcite, prehnite, and rare stilbite.  Th
K-Ar dates (on hornblende) in granodiorites yielded the following ages:  134 +/- 7, 142 +/- 4, 145 +/- 4, 142 +/- 4, and 141 +/- 5 my
Chitna Valley batholith
Chiefly quartz monzodiorite, but compositionally diverse, ranging from granite to diorite.  Generally foliated and locally gniessic, especially in plutons enclosed in the Strelna Metamorphics
K-Ar ages range from 157 to 138 Ma with foliated phases yielding datas as young as 122 Ma
Chitina valley batholith - Wrangellia Terrane
Chiefly quartz monzodiorite, but compositionally diverse ranging from granite to diorite.  Generally foliated and locally gneissic, especially in plutons enclosed in the Strelna Metamorphics (PPasm)
K-Ar dates indicate plutonic ages of 138-157 Ma; ages and foliated phases are as young as 122 Ma
Jmp
Mafic plutonic complex
Early or Middle Jurassic
Consists dominantly of layered hornblende-pyroxene gabbro and leucogabbro, with minor ultramafic, dioritic, and tonalitic rocks.  The southern margin of complex is a major fault zone; cataclastic modification of mineral layering in the complex near the f
K-Ar ages on low-potassium hornblende and chloritized biotite range from 153 to 171 Ma.
Jgl
Hornblende gabbro and leucogabbro
Layered gabbro and leucogabbro; layered gabbro is dominantly hornblende gabbro; hornblende-augite gabbro is common, however, with the hornblende replacing or molded upon the augite; and layers and lenses of hornblendite occur at several places.  Mafic pa
K-Ar ages on hornblende of 419 +/-21, 188 +/-8, and 171 +/- 5 Ma; the older age is considered suspect.
shgb
Schistose hornblende gabbro; Metamorphic Complex of Gulkana River
Late Jurassic or older
Schistose hornblende gabbro
scgb
Schistose clinopyroxene gabbro; Metamorphic Complex of Gulkana River
Schistose clinopyroxene gabbro
Klc
Schist of Liberty Creek
mid-Cretaceous? or Jurassic??
Well-foliated, multiply-deformed greenschist and transitional blueschist facies mafic metavolcanic and metasedimentary rocks.  Schistocity is well-developed although primary sedimentary or volcaniclastic features are retained locally.  There are no marke
Jgb
Greenschist and transitional blueschist
Chiefly intercalated greenschist and blueschist, but includes lawsonite, muscovite, or actinolite schist, carbonaceous schist, highly siliceous rocks containing stilpnomelane, and foliated calcareous rocks.  Similar to Raspberry, Seldovia, and Knik River
K-Ar ages on crossite and muscovite range from 152 to 175 Ma, thought to be metamorphic ages.
JTrm
McCarthy Formation -- lower member
Early Jurassic? and Late Triassic (Norian)
Marine limestone, shale, and chert.  Lower member consists of interbedded finely-laminated, dark-gray, impure limestone, subordinate fissile shale, and minor chert.
Monotis and both calcareous and silicieous microfossils.
Minimum age from intruding granodiorite of 144 Ma
McCarthy Formation
Early Jurassic and Late Triassic
Formerly named McCarthy Shales.  Upper: thin bedded, fine-grained spiculite, impure chert, impure limestone, and shale; Lower: thin-bedded impure limestone (wackestone), calcareous carbonaceous shale, and impure, locally spiculitic, chert.  Temporal, but
Upper: 'paleontological evidence' indicates an age span from Hettangian to Pliensbachian Lower: Monotis pelecypods and other 'fossils' indicate Norian age
Named by MacKevett (1963) for exposures in the Wrangell Mountains.  Exposed in Bering Glacier D-2 quadrangle only along the south side of the Chitina River where it consists of a few hundred meters of consists mostly of dark-gray to black, calcareous car
Paleontologic evidence (cited in MacKevett, 1970a, b; 1971, p. 15, 29) documents Early Jurassic ages that range from Hettangian to Pliensbachian Stages
JTrml
McCarthy Formation - Lower member
Early Jurassic and Late Triassic, Norian
Impure limestone (wackestone and subordinate lime mudstone) intercalated with shale (dark gray, fissile, finely laminated calcareous carbonaceous containing abundant microfossils) and minor chert (gray/brownish-black microcrystalline silica).  Limestone
Widespread pelecypods of the genus Monotis indicate the late Norian Stage of the Late Triassic found in the lower parts of the member
Limestone
Late Triassic
Upper Part: thin-bedded, fine-grained limestone, interbedded with thin beds of  argillite and carbonaceous shale.  Minor beds of calcareous sandstone and grit  Lower Part: fine-grained, massive limestone with chert lenses
Monotis subcircularis; hydrozoa (Lovcenipora?); Spondylspira
Trtl
Thin-bedded limestone
Dark-gray fine-grained limestone thick with thin interbeds of dark carbonaceous shale.
Trml
Massive limestone
Massive limestone with lenses and modules of black and gray chert and irregular patchworks of disseminated fine-grained quartz.  Commonly strongly brecciated and veined by coarsely crystaline calcite.
Fine-grained limestone in beds (<2 m) interbedded with carbonaceous shale and argillite.  Chiefly micrite and biomicrite, locally dolomitized.  Contact metamorphism with quartz diorite produced a garnet-rich calc-silicate skarn locally containing dissemi
Age based on fossil evidence in Nabesna C-5
Massive fine-grained limestone.  Locally abundant lenses of chert and irregular patchwork of siliceous material.  Chiefly micrite and microsparite, locally dolomitized.  Contact metamorphism with quartz diorite produced a garnet-rich calc-silicate skarn
Chitistone and Nizina Limestones
Late Triassic (Karnian and Norian)
Light- to medium-gray limestone of diverse textural varieties and include minor dolomite lower in the sequence and nodules and lenses of dark-gray chert high in the sequence.  Lower thicker-bedded sequence is Chitistone Limestone, upper, thinner-bedded s
Trcn
Chritistone and Nizina Limestones
Both have marked lateral changes in thickness.  Lowest Chitistine: dolomite algal-mat chips, stromatolites and evaporites.  Upper Chitistine: diverse limestone including lime mudstones, wackestone, packstone, and grainstone.  Nizina: diverse limestone wi
Chitistone: Tropites indicate a Karnian age.  Nizina: ammonites and pelecypods indicate an age span from Late Karnian to Middle Norian
Trm
Marble
Fine- to medium-grained calcite-rich marble, locally dolomitic, sometimes schitose or banded.  Contact-metamorphosed  Chritistone and Nizina Limestones, near granitic plutons of the Chitina Valley batholith.
Trn
Late and Middle Triassic
The limestone is medium- to thick-bedded, white to medium gray, and commonly emits fetid odors when freshly broken. Undifferentiated Chitistone and Nizina limestones occur locally along the south side of the Chitina River in the D-2 quadrangle and betwee
Unfossiliferous; in the McCarthy quadrangle to the north, diagnostic fossils indicate a Late Triassic age (MacKevett, 1978).
Trnz
Nizina Limestone
Late Triassic, Norian and Karnian
Rocks consist of thin-bedded limestone (shades of gray, fine-grained wackestone and lime mudstone with a hackly fracture) and abundant greenish-black chert in thin lenses.  Unit has been cut by the Chitina batholith and Tertiary hypabyssal rocks
Sponge spicules, radiolarians, and comminuted shelly debris occur in the upper strata.  Poorly preserved, fragmented pelecypods of the genus Halobia were found
Trnzm
Nizina Limestone - Marble
Generally consists of fine-grained granoblastic calcite with minor bands of diopside and epidote.  Locallized into small masses that have been recrystallized near the Chitina Valley batholith
Trc
Chitistone Limestone
Late Triassic, Karnian
Medium to thick bedded lime mudstone (dark greenish gray, fine-grained and incipiently recrystallized), and less abundant wackestone.  Limy dolomite and dolomitic limestone in lower strata reflecting sabkha facies.  Widespread calcite veinlets, and poorl
Undiagnostic comminuted remains of echinoids and gastropods.  Elsewhere  the Chitistone is documented by the ammonite Tropites
Trcm
Chitistone Limestone - Marble
Small masses of marble and skarn near the granodiorite of the Chitina Valley batholith.  Locally banded, the marble is fine to medium grained granoblastic calcite.  The skarn consists mainly of diopside and has local pods and disseminations of pyrite, py
Chiefly limestone and dolostone; minor chert and marble.  Both units locally fossiliferous
Abundant algal-mat chips and stromatolites,
Conglomerate and shale
Middle Triassic
Intermixed conglomerate and carbonaceous shale and argillite.  Conglomerate contains subangular to rounded clasts
Shale beds contain abundant Daonella of Middle Triassic age
Trg
Gabbro
Late and (or) Middle Triassic
Medium- to coarse-grained, subophitiic gabbro
Gabbro and diabase and gabbronorite dikes -- Wrangellia Terrane
Late Triassic (?)
Clinopyroxene-hornblende gabbro and diabase and gabbronorite dikes
Trcg
Stocks and plugs -- Wrangellia Terrane
Clinopyroxene-hornblende stocks and plugs
Late Middle Triassic and Early Late Triassic, Karnian and Ladinian
Rock is dark green gray, fine to meduim grained, subophitic; interpreted as feeders and progenitors of Nikolai basaltic lavas.  Having rare porphyritic phases, unit forms small plutons, dikes and sills cutting, predominantly, the Hasen Creek Formation wi
JTrs
Quartz-feldspar schist and cataclastite
Part of "diorite complex."  Quartz-feldspar schist and cataclastite
JTrg
Pink biotite-hornblende syenite-monzonite gneiss
Part of "diorite complex."  Pink biotite-hornblende syenite -monzonite gneiss with thin layers of gray hornblende diorite gneiss, and minor dark biotite schist.  Small syenite pegmatite dikes
Nikolai Greenstone
Middle and (or) Late Triassic
Weakly metamorphosed, lightly altered tholeiitic basalt that is characteristically amygdaloidal and poorly bedded.  Metamorphosed to prehnite-pumpellyite facies
K-Ar whole-rock isochron of 112 +/- 11 Ma thought to indicate collosion of Wrangellia with North America
Dominently slightly porphyritic tholeiitic basalt sequence;  basal sections include pillow basalt and intercalated argillite;  basal sections elsewhere are volcanic conglomerate with dominent intermixed pahoehoe and aa, typically altered and locally meta
Ladinian aged pelecypods and Karnian aged ammonites
Triassic
Subaerial porphyritic basalt flows interbedded with volcaniclastic rocks; basal sections include volcanic conglomerate-breccia with dominent intermixed pahoehoe and aa
Trng
Dominantly thick flow units of slightly porphyritic tholeiitic basalt with medium-grained plagioclase (labradorite) and less abundant clinopyroxene phenocrysts in fine-grained intergranular groundmasses rich in plagioclase and clinopyroxene.  Characteris
Amygdaloidal tholeiitic basalt lava flows and minor associated volcaniclastic rocks.  Pillow structures common along lower Ptarmigan Creek, but lavas are typically subaerial
Amygdaloidal basalt flows separated locally by volcaniclastic beds.  Intermixed aa and pahoehoe flows with individual flow units.
Late and (or) Middle Triassic)
Wrangellia terrane, Nikolai Greenstone
Upper and/or Middle Triassic
Green amygdaloidal basalt flows, separated by locally thin volcaniclastic beds.  Intermixed aa and pahoehoe flows.  Rocks largely thermally metamorphosed to fine-grained assemblages of actinolite, epidote, and chlorite.  Includes a number of Triassic gab
A voluminous undifferentiated tholeiitic basalt that attains a composite thickness of 3000 m.  Unit is composed of very fine to fine grained flows which contain abundant amygdules and is partially porphyritic.  It has been intruded by the Chitina Valley
GG
Gabbroic phaciods in McHugh Complex
Jurassic and Late Triassic(?)
Strongly altered gabbroic phacoids that are tectonic inclusions in the McHugh Complex
VA004
ds
Dadina schist
Late Paleozoic (?) or older
Coarse quartz-biotite schist, altered and cataclastic meta-andesite, over lain(?) by amphibolite schist, mica-schist, and minor meta-limestone.  Intruded by unmetamorphosed coarse-grained quartz diorite dikes.  Also includes sheared meta-gabbro.  Dadina
Kag
Haley Creek terrane -- metaplutonic rocks
K-Ar ages on hornblende range from 122 to 148 Ma.  A muscovite age is 133 +/- 4 Ma
Jag
Uranatina River metaplutonic unit
Jurassic and Middle Pennsylvanian
Portion of tectonic inclusion 10 by 15 km in McHugh Complex consisting of layered quartz gabbro, amphibolite, and orthogneiss.  This unit consists of compositionally banded very mafic amphibolite to hornblende-biotie dioritic and quartz dioritic gneiss.
Low-potassium hornblende yielded K-Ar age of 267 +/- 8 Ma (mid-Permian), thought to approximate time of metamorphism.
sqm
Schistose quartz monzonite; Metamorphic Complex of Gulkana River
Schistose quartz monzonite
sqd
Schistose quartz diorite; Metamorphic Complex of Gulkana River
Schistose quartz diorite
sgd
Schistose granodiorite; Metamorphic Complex of Gulkana River
Schistose granodiorite
shd
Schistose hornblende diorite; Metamorphic Complex of Gulkana River
Schistose hornblende diorite
ag
Amphibolite gneiss; Metamorphic Complex of Gulkana River
Amphibolite gneiss
Pzs
Skolai Group -- greenstone unit
Late Paleozoic, Middle Pennsylvanian to Early Permian
Diverse Upper Paleozoic volcanic, volcaniclastic, and marine sedimentary rocks.  Unit consists largely of two lithologies, map unit Pzs is dark, greenish-gray poorly bedded greenstone, characterized by prehnite-pumpellyite mineral assemblages, locally re
Pzg
Gabbro and leucogabbro
Late Paleozoic, Permian to Pennsylvanian
Gabbroic rocks rocks consisting of sills, dikes, and discordant plutons.  Medium- to coarse-grained, massive to foliated, altered gabbro, leucogabbro, and minor diorite.  Coextensive with layered gabbro in the McCarthy quadrangle.
K-Ar age on actinolitic amphibole of 246 +/- 12 Ma, thought to be minimum age, may be partially reset by intrusion of nearby Late Jurassic hornblende granodiorite pluton.
Pgo
Gabbro and Orthogneiss
Pennsylvanian
Interlayered quartz monzonite gneiss, monzonite gneiss, and associated altered and foliated gabbro, with minor dioritic phases.  Gabbro and orthogneiss extend into Valdez Quad.
Biotite of the gneiss yields a radiometric date of 271+11 m.y.
Gabbro and Anorthosite
Late Paleozoic (?)
Medium-grained leucocratic gabbro and hornblende gabbro mixed with altered anorthosite
Pzum
Serpentinized peridotite (lherzolite) and dunite
Pu
Serpentinized alpine-type, intensly sheared, ultramafic rock; includes some partly serpentinized gabbro.  Correlates with ultramafic rocks of Nabesna Quad.
mha
Metamorphosed hornblende andesite; Metamorphic Complex of Gulkana River
Metamorphosed hornblende andesite
PPasm
Metamorphosed Skolai Group
Early Permian and Pennsylvanian
Greenschist- to amphibolite-facies metamorphic rocks, mainly schist, phyllite, amphibolite, and marble.  Corresponds to the Mississippian Strelna Formation.
'Fossil collections' indicate an Early Permian age.
PPs
Skolai Group
Wrangellia terrane, Skolai Group
Ps
Slana Spur Formation
Early Permian
Part of Mankomen Group.  Volcanic siltstone, sandstone, and conglomerate with subordinate lapilli tuff, volcanic breccia and impure biomicritic limestone.   Equivalent to parts of the Cache Creek Group and the Skolai Group
Middle and Late Pennsylvanian and Early Permian
Pzvc
Late Paleozoic
Dark-gray thin-bedded fine- to medium-grained volcanic sandstone, cherty argillite, quartzite, and tuff.  Weakly metamorphosed (greenschist facies). May be equivalent to Tetlna Volcanics (PPt) or Devonian terrane (Dp).
Pzv
Late (?) Paleozoic
Dark-greenish-gray fine-grained to weakly porphyritic andesite and basalt flows with abundant reddish jasperoid breccia, and minor intebeds of red and green cherty mudstone. Weakly metamorphosed (greenschist facies). May be equivalent to Tetlna Volcanics
mcb
Metamorphosed clinopyroxene basalt; Metamorphic Complex of Gulkana River
Metamorphosed clinopyroxene basalt
am
Amphibolite; Metamorphic Complex of Gulkana River
Amphibolite
Ph
Hasen Creek Formation
Argillite, shale, sandstone, chert, limestone, and minor conglomerate.  Locally thermally metamorphosed near Jurassic plutons.
Permian
Marine argillite and minor sandstone and chert, locally fossiliferous.  May include some volcaniclastic rocks.  Abundant Triassic gabbro sills.  Correlative with the Mankomen Group in Nabesna quadrangle
Skolai Group - Hasen Creek Formation
Early Permian, Guadalupian, Leonardian, and Wolfcampian
Weakly metamorphosed, diverse, thin bedded argillite, with less abundant lithic graywacke, conglomerate, shale, chert, schist, marble, and limestone (carbonates are unit Phl).  The argillite and shale are shades of gray, yellowish brown, fine grained, si
Phl
Skolai Group - Limestone and marble
The limestone predominantly occurs at the base of the section and sporadically ditributed limestone and marble elsewhere.  Coarse-grained bioclastic grainstone with local conglomeratic facies (containing pebbles derived from the Station Creek and Hansen
Abundant crinoid columnals and lesser brachiopods, bryozoans, and gastropods.  The multiple species of the brachiopod assemblage represents typical arctic Permian fauna of late Leonardian to early Guadalupian age
Pl
Limestone of the Hasen Creek Formation
Thin- to thick-bedded, fossiliferous, limestone.  Includes Golden Horn Limestone Lentil.  Correlates with the Eagle Creek Formation of the Mankomen Group in eastern Alaska Range in Nabesna Quad.  Also correlates with Cache Creek Group of Yukon Territory.
Corals, crinoids, brachiopods, bryozoans,fusilinid indicate Early Permian (Wolfcampian)
Thin unit (10-30 m) of sand- and silt-rich limestone that appears to separate sedimentary rocks of the Hasen Creek Fm (Ph) from the underlying volcaniclastic rocks of the Station Creek Fm (PlPsc).  Found in small block of Paleozoic and Mesozoic rocks nor
abundant crinoid and coral fragments
Pel
Part of Mankomen Group.  Thin- to thick-bedded fossiliferous limestone occuring at the base of the Eagle Creek Formation.  Base is a coarse-grained clastic limestone.  Gabbroic dikes and sills.  Equivalent to parts of the Cache Creek Group and the Skolai
Pm
Monzonitic-Granitic Complex
Medium-grained, equigranular granitic rocks with fine- to coarse-grained variants.  Abundant granite and quartz monzonite and some quartz syenite, syenite, and monzonite, with border zones of quartz monzodiorite, monzodiorite, and gabbro.  In both the Be
Hornblende of monzonite and quartz monzonite gives age of 295+8 and 297+9 m.y..
Pam
Monzonite, syenite, gabbro
Middle Pennsylvanian
Massive to schistose, medium- to coarse-grained monzonite, syenite, gabbro, contains local inclusions of meta-andesite.  Chiefly pink to gray-green monzonite and syenite, consisting of hornblende, K-spar, biotite, and plagioclase with local K-spar rich a
Pag
Diorite and quartz diorite
middle Paleozoic(?) and older(?) (Pennsylvanian?)
Granite and syenite, medium- to coarse-grained, and schistose. Syenite chiefly schistose, gray-green hornblende-Kspar-biotite-plagioclase syenite. Local K-spar rich areas up to 8 cm diameter. Contains local inclusions of meta-andesite.
PPf
Ahtell Pluton
Permian and Pennsylvanian
Fine-grained biotite granite
PPp
Porphyritic hornblende granodiorite
PPg
Biotite-hornblende granite and granodiorite
JTrd
Part of "diorite complex."  Hornblende diorite with subordinate hornblende granodiorite, hornblende-biotite quartz monzonite, biotite quartz monzonite, hornblende diorite gneiss, clinopyroxene-hornblende gneiss, hypersthene-hornblende gneiss, and amphibo
Mza
Anorthosite
Mesozoic
Part of "diorite complex."  Medium- to coarse-grained bytownite anorthosite with hypidiomorphic to allotriomorphic texture.  Diopside pyroxene and gabbro pegmatite
PPa
Diorite Complex
Altered diabase and gabbronorite
PPd
Diorite, granodiorite, and gabbronorite
Psm
Strelna Metamorphic Complex
Mesozoic or Paleozoic
A diverse and intimately mixed group of low- to medium-grade greenschist and amphibolite which also includes abundant pelitic and psammitic schist, metachert, and gneiss having pronouced mortar structure.  Contains no marble but does contain extensive ma
K-Ar age on hornblende from metagabbro of 152 +/- 6 Ma; thought to be reset.
Amphibolite facies rocks
Jurassic(?)
Portion of tectonic inclusion 10 by 15 km in McHugh Complex consisting of layered quartz gabbro, amphibolite, and orthogneiss.  This unit consists of nondescript, amphibolite facies, weakly foliated to nonfoliated granular rocks of uncertain protolith.
qmfs
Quartz-muscovite-feldspar schist; Metamorphic Complex of Gulkana River
Quartz-muscovite-feldspar schist
mmp
Metamorphosed pelitic and calc-schist; Metamorphic Complex of Gulkana River
Metamorphosed pelitic and calc-schist
Pas
Strelna Metamorphics, Metasedimentary and metavolcanic rocks
Pennsylvanian, and older(?)
Metasedimentary and metavolcanic rocks.  Dominantly interlayered quartz-feldspar mica schist and mica-quartz schist and subordinate marble beds or lenses.
JPhc
Haley Creek metamorphic assemblage
Late Jurassic and Pennsylvanian or older?
Wrangellia terrane, Haley Creek metamorphic assemblage, Consists of Uranatina River metaplutonic unit (Jurassic and Pennsylvanian) and Strelna Metamorphics (Early Pennsylvanian and older?)
Mankomen Group (undivided)
Thermally altered, weakly foliated, Mankomen Group.  Wollaston-, diopside-, and garnet-bearing marble, calcareous metasiltstone and metasandstone, and pyroxene and hornblende hornfels
Mankomen Group
Lower Permian
Argillite with subordinate interbedded calcareous siltstone and grit.  Alternating beds of argillite and siltstone, grading to silty limestone showing a ribbon-like appearance in the upper strata.  Locally intruded by gabbro dikes and sills of Triassic a
Cephlapods, brachiopods, and corals indicate an Early Permian age
Pe
Eagle Creek Formation
Part of Mankomen Group.  Thin-bedded argillite and siliceous siltstone, with interbedded of calcereous siltstone and sandstone, biomicritic limestone, and  a pebble to cobble conglomerate.  Gabbroic dikes and sills.  Equivalent to parts of the Cache Cree
Daonella; Abundant brachiopods, cephalopods, corals, foraminifera, and bryozoan
Pzm
Skolai Group -- marble unit
Subordinate light- or medium-gray and buff calcareous rocks, mostly recrystallized to marble but containing scanty fragments of fossils, interbedded with dark-gray calcareous siltstone and shale.  Change unit designator to ma, per Winkler (1998)
Scanty fragments of bryozoans, crinoids, corals, and brachiopods.
M
Haley Creek terrane -- schistose marble
Schistose marble.  Individual marble layers can be traced for several km, however the layers vary greatly in thickness, terminate abruptly in places, and are generally thoroughly folded.  Small isolated bodies of marble mark unmapped fault within the Hal
Marble of the metamorphosed Skolai Group
Fine- to medium-grained banded impure marble, locally deformed.  Interpreted as temporal equivalent of limestones of the Hasen Creek Formation
Poorly preserved Early Permian fossils
Pasm
Strelna Metamorphics, Marble
Early Pennsylvanian
White to gray marble (m) forms conspicuous deformed and folded bands and pods throughout the unit.  Individual marble beds vary markedly in thickness along strike; maximum .measured thickness of the unit is about 1,200 meters. The unit is commonly compos
PPasc
Station Creek Formation
A volcanoclastics member, which grades from coarse volcanic breccia through volcanic graywacke to volcanilutite;  Also a volcanic flow member, locally pillowed and brecciated, and includes altered lavas of andesites and basalts, and minor intercalated vo
PlPsc
Pennsylvanian and Permian
Chlorite-rich amygdaloidal andesitic lava flows and volcaniclastic rocks.  Correlative with the Tetelna Volcanics in the Nabesna quadrangle
PPasvc
Station Creek Formation - Volcaniclastic member
Lower Permian, Early and Middle Pennsylvanian
A volcanic pebble conglomerate and coarse volcanic graywacke with subordinate intercalated broken-pillow breccia and volcanic flows.  Mainly greenish-gray, the rocks are generally metamorphosed to greenschist
Pasmv
Station Creek Formation - Volcanic flow member
Dark greenish-gray metaandesite or metabasalt flows and some compositionally similar broken-pillow lavas metamorphosed to greenschist.  Pillow structures are preserved in several flows.  The unit is locally cut by gabbro dikes.
PPt
Tetelna Volcanics
Volcanic flows of porphyritic andesite, volcanic mud and debris avalances, lapilli-pumice tuffs, and fine- to coarse-grained volcaniclastics ranging from mudstone to conglomerate, and volcanic-rich limestone.  Areas of contact metamorphism creating folia
Brachiopods and cephalopods
Pt
Tetelna Volcanics, hornblende andesite and other volcanic rocks, metamorphosed to greenschist facies.
PPat
Interbedded volcanic flows, volcanic mud and debris avalanches, lapilli-pumice tuffs, volcanic mudstone to volcanic sandstone, and volcanic pebble conglomerates all intruded by gabbro dikes and sills.  Volcanic rocks chiefly andesite and dacite in compos
Interbedded flows of andesite, massive lahars, lapilli-pumice tuffs, and volcaniclastic rocks ranging from mudstone to conglomerate, locally graded
Dl
Devonian
Gray to dark-gray recrystallized limestone.  Regionally metamorphosed (greenschist facies)
Rugose and tabulate corals
MzPzi
Diorite-gabbro
Dark-greenish-gray, fine- to coarse-grained augite- and hornblende-bearing mafic diorite and gabbro.  Regionally metamorphosed (greenschist facies)
Pzk
Kaskawulsh Group of Kindle
Devonian (?) and Older (?) Paleozoic
Mainly thick-bedded, fine- to coarse-grained, locally schistose, banded, or granulated marble, also schist, phyllite, and minor amphibolite, all strongly schistose.
Tabulate horn corals suggest a Devonian age
Dkm
Kaskawulsh Group, Calcschist
early Late or Middle Devonian
Massive to thick-bedded, gray to white fine- to coarse-grained marble, dolomite, and muscovite-quartz-calcite schist; commonly complexly and tightly folded into isoclines.
Contains sparse tabulate corals and Amphipora of Middle or early Late Devonian age
Kaskawulsh Group -- marble
Devonian and older(?)
Massive to thin-bedded white, gray, and black marble in complexly folded beds and lenses totalling more than 1,000-m-thick.
Metasedimentary and meta-igneous rocks
Devonian and older (?)
Coasre grained recrystallized limestone.  Locally fossiliferous.
Dp
Phyllite
Dark- to light-gray phyllite and brownish-gray metaconglomerate, containing clasts of quartz mica schist, quartzite, calcareous mica schist, quartz-chlorite schist and thin marble lenses.  Regionally thermally metamorphosed (greenschist facies)
Kaskawulsh Group, Metavolcanic rocks
Mississppian to Ordovician
Chiefly schistose, fine-grained metaandesite tuff and flows, and coarse-grained breccia and conglomerate, along with minor dark-gray argillite. Metavolcanic and volcaniclastic rocks massive to crudely layered.  Metavolcanic breccia and conglomerate conta
Pav
Metamorphic rocks between Border Ranges and Hubbard Faults, Metavolcanic rocks
Mainly dark green metatuff with minor carbonate and chert
Pavs
Metamorphic rocks between Border Ranges and Hubbard Faults, Metasedimentary and metavolcanic rocks
Pzvp
Kaskawulsh Group -- interbedded metavolcanic and metasedimentary rocks
Foliated and doubly folded massive to thinly banded mafic metavolcanic rocks; typically greenschist, semischist to mica schist, and thin pods and beds of marble.
Kaskawulsh Group -- metavolcanic rocks
Massive to thinly banded, green to greenish black recrystallized mafic volcanic rocks
Dms
Dark-gray phyllite, dark-gray to buff quartzite, calcareous quartzite, porcellanite, buff to light-gray calcareous quartz mica schist, and light-gray marble.  Regionally metamorphosed (greenschist facies)
Chiefly phyllite with subordinate schistose pebble conglomerate, containing stretched clasts of quartzite, limestone, schist, and phyllite, gray micaceous quartzite, and calcareous quartz-mica schist.
Dhp
Hornfelsed phyllite.  Cordierite- and andalusite-bearing knotty schists peripheral mostly to the Mineral Cairn phase (Kmg) of the Tok-Tetlin pluton.
Dg
Dark-greenish-gray massive greenstone.  Locally contains thin septa of phyllite.  Regionally metamorphosed (greenschist facies)
Massive greenstone, consisting of fine-grained epidote, chlorite, and altered feldspar with segregations of actinolite and occasional small phenocrysts of clinopyroxene.  May be intrusive.
Quartz mica schist
Early(?) Paleozoic
Tan, light-gray, and light-gray-green quartz-muscovite schist, quartz-muscovite-chlorite schist, dark-gray graphitic schist, and minor calcareous mica schist.  Regionally metamorphosed (greenschist facies)
Pzp
Kaskawulsh Group -- metasiltite
Dark-reddish brown weathering, black massive meta-siltstone interbedded with marble.
VA008
VA006
Chiefly talus but includes deposits of small landslides, rock glaciers, and other mass-wasting processes.  Generally includes a large proportion of alluvium in small fans and cones and reworked glacial deposits.  Sand, gravel, boulders, diamicton, and ru
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
Slumps, earth-debris flows, block glides, and debris avalanches.  Diamicton and rubble
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
In ponds, swamps, lagoons, and along low-gradient streams.  Chiefly silt, clay, fine sand, peat, and other organic material
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
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
Copper River deposits
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
overprint
Well-defined lobate forms that may include glacier ice cores.  Chiefly blocks of rubble
Neoglacial deposits of end, lateral, and ground moraines, kames and outwash proximal to present glaciers; includes small rock glaciers.  Diamicton, local gravel, and sand
Valdez Group -- Amphibolite-facies flysch
Flysch metamorphosed to amphibolite-facies schist
JTrt
Early Jurassic and Late Triassic(?)
Dominantly andesitic volcaniclastic rocks, products of Late Triassic and Early Jurassic oceanic volcanic arc
Jnt
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
K-Ar dates indicate ages of 188-171 Ma
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
K-Ar dates indicate plutonic ages of 157-138 Ma, foliated phase ages are as young as 122 Ma
Mafic and ultramafic rocks
Gabbro, pyroxenite, peridotite and dunite.  Includes the Nelchina River Gabbronorite, the Tonsina ultramafic, and a mafic sequence of Winkler and others (1980).
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
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
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
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.
PPas
Skolai Group, undivided
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
Not mapped
Quarternary, Pleistocene
Olivine basalt and basaltic andesite
Shield lavas -- Mount Wrangell volcano
Holocene and Pleistocene, 0.65 Ma and younger
Chiefly andesitic flows
Volcanic debris flows
Shield and intracaldera lavas -- Mount Jarvis volcanoes
Pleistocene, 1.7-1.0 Ma
Extensive flat-lying andesitic flows
Lava flows and sedimentary rocks -- Older volcanic and sedimentary rocks
Pleistocene, Pliocene, or Miocene
Flat-lying andesite and dacite lava flows; a Tertiary tillite and the fossil-rich conglomeratic sandstone Frederika Formation
Domes and intrusive rocks -- Older volcanic and sedimentary rocks
Tw
Lava flows and lahars -- Older volcanic rocks
Miocene or Oligocene
Basaltic andesite, andesite, and dacite lava flows; andesitic lahar deposits
Granodiorite -- Hypabyssal and plutonic rocks
Pleistocene, Pliocene, Miocene, or Oligocene
Plutonic phase of the Wrangell Lava exposed mainly at Hawkins Glacier head, marginal to Mount Blackburn volcano caldera
Marine sedimentary rocks -- Wrangellia terrane
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
Mlange 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
Greenschist-facies flysch -- Valdez Group
Flysch metamorphosed to lower greenschist-facies.  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.  Metamorphic grade increase
Spiculite, impure chert and limestone, and shale deposited in a starved marine basin environment
Fossils locally abundant
Triassic limestone
Locally fossil-rich, thin-bedded limestone and interbedded argillite in partially starved marine basin; overlies shallow marine to intertidal fossil-poor cherty massive limestone
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
Altered tholeiitic basalt.  Largely subareial, locally submarine in northeastern part of quadrangle. where basal sections contain pillow basalt and intercalated argillite.  elsewhere, base generally characterized by volcanic conglomerate as much as 70-m-
Late and(or) Middle Triassic
Widespread sequence of tholeiitic flood basalt flows, mainly subaerial and characteristically amygdaloidal, include subordinate volcaniclastic interbeds and volcanic conglomerate basal sections.  Metamorphosed to prehnite-pumpellyite facies although alte
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
PPam
Permian, 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)
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
In active streambeds and lowest terraces along larger streams and active alluvial fans.  Chiefly well sorted gravel and sand; minor silt and boulders
CV004
Colluvium consisting of talus and small landslides, also includes small glacial, rock glacier, and alluvial deposits.  Sand, gravel, boulders, diamicton, and rubble
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
Dacite, andesite, and rhyodacite porphyry.  Typically strongly porphyoritic.  Correlates with younger porphyry of Nabesna quadrangle and with hypabyssal rocks associated with the Wrangell Lava in Alaska and Canada