Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska

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Title:
Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska
Abstract:
This report provides detailed (1:63,360-scale) mapping of the Tanana A-1 and A-2 quadrangles (500 square miles; equivalent to eight 7.5-minute quadrangles). The area is part of the Manley Hot Springs-Tofty mining districts and adjacent to the Rampart mining district to the south of the Tanana B-1 Quadrangle. This report includes detailed bedrock, surficial, structural, and stratigraphic data. Based on the resulting geologic maps, field investigations, and laboratory materials analyses, the report also includes derivative maps of geologic construction materials and geologic hazards. The Tanana A-1 and A-2 Quadrangles and surrounding area comprise several isolated mountainous ridges in the western Yukon-Tanana Upland of interior Alaska.
Supplemental_Information:
The layers listed below are present as ArcGIS shape files. Attribute information for the following layers (entities) is included in this metadata file under the "Entity_and_Attribute_Information" section. Each layer is listed and described in detail under its own heading starting "Entity_Type_Label." The numerical value(s) "1" and/or "2" included in the layer names correspond to the quadrangle(s) Tanana A-1 and/or Tanana A-2, respectively. Layers include:
hflsa1_comp_polygon     comprehensive geologic unit polygons (hornfels)
hflsa2_comp_polygon     comprehensive geologic unit polygons (hornfels)
tana12_att_point     points for the strike, dip, and plunge of bedding planes, foliation, and various lineaments
tana1bedcon_arc     comprehensive geologic unit contacts
tana1bur_arc     vector lines for various types of geophysical features
tana1comp_polygon     comprehensive geologic unit polygons
tana1fld_point     points and vector lines for types of anticlines or synclines
tana1fldline_arc     types of folds, anticlines, synclines, or lines depicting a cross-section
tana1srf_polygon     comprehensive geologic polygons
tana1strline_arc     vector lines for types of faults
tana2bedcon_arc     comprehensive geologic unit contacts
tana2bur_arc     vector lines for various types of geophysical features
tana2comp_polygon     comprehensive geologic unit polygons
tana2fld_point     points and vector lines for types of anticlines or synclines
tana2fldline_arc     types of folds, anticlines, synclines, or lines depicting a cross-section
tana2srf_polygon     comprehensive geologic polygons
tana2strline_arc     vector lines for types of faults
  1. How should this data set be cited?

    Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Pinney, D.S., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Public Data File PDF 98-37A v 1.1, State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (DGGS), Fairbanks, AK, USA.

    Online Links:

    Other_Citation_Details: text report, 19 p., 1 sheet, scale 1:63,360

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -151.018782
    East_Bounding_Coordinate: -149.971866
    North_Bounding_Coordinate: 65.259054
    South_Bounding_Coordinate: 64.990820

  3. What does it look like?

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 1997
    Ending_Date: 1998
    Currentness_Reference: publication date

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: map and vector digital data

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

    2. What coordinate system is used to represent geographic features?

      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 5
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -153.000000
      Latitude_of_Projection_Origin: 0.000000
      False_Easting: 500000.000000
      False_Northing: 0.000000

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.000064
      Ordinates (y-coordinates) are specified to the nearest 0.000064
      Planar coordinates are specified in meters

      The horizontal datum used is D_Clarke_1866.
      The ellipsoid used is Clarke 1866.
      The semi-major axis of the ellipsoid used is 6,378,206.4.
      The flattening of the ellipsoid used is 1/294.978698.

  7. How does the data set describe geographic features?

    tana1comp_polygon.shp
    Object type is vector, there are 1064 rows associated with this entity, and the entity values refer to comprehensive geologic polygons (Source: Alaska Division of Geological & Geophysical Surveys)

    BUNIT
    Interpretive geologic map unit labels (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    KwcvWilber Creek unit siliciclastic and volcaniclastic rocks (late Albian(?): Weber and others, 1992)-Very dark gray to dark greenish dark gray, volcanic clast-bearing, poorly sorted, sub-angular, medium- to coarse-grained, marine, argillaceous lithic sandstone, shale and siltstone. Estimates of the framework grain composition are: 55 percent chert, 25 percent quartz, 15 percent plagioclase (which includes about 5 percent obvious volcanic clasts), and 5 percent sedimentary and metamorphic rock fragments, and minor white mica.
    KwcsWilber Creek unit sandstone, shale, siltstone, undivided (Albian: Weber and others, 1992)-Very dark gray to dark greenish gray, poorly sorted, marine, argillaceous lithic sandstone, shale and siltstone containing white mica-bearing argillaceous sandstone as laminae and thin interbeds; rare conglomerate. Beds are typically thin, parallel, laterally continuous, sharp-based, and graded; from fine- to medium-grained at the base, grading up to silt at the top of beds.
    KJwqWolverine quartzite unit (Early Cretaceous and Late Jurassic: Weber and others, 1992)-Very light gray to tan, white- to medium gray-weathering, moderately well sorted, sub-rounded, fine- to medium-grained quartzite, and sublitharenite with interbedded shaley rocks. Estimates of sandstone clast composition indicate greater than 90 percent quartz (rare light-blue color), two to five percent chert, and locally trace amounts of feldspar and white mica.
    KJwsWolverine quartzite unit sandstone and shale-undivided (Early Cretaceous and Late Jurassic: Weber and others, 1992)-Medium gray to light gray, locally black, lichen-covered, quartz-rich sandstone and interbedded shale. Sandstone is silica-cemented, well indurated quartzarenite but lacks the prominent outcrop pattern, continuity, and thickness of the quartzite unit (map unit 'KJwq').
    TrPs***Note: typographical error exists on the Preliminary Geologic Map of the Tanana A-1 and A-2 Quadrangles, Central Alaska (Publication PDF98-37A-SH1). Unit TrPa does not exist. Unit label should read TrPs.*** Argillite, sandstone and shale (Triassic and Permian: Reifenstuhl and others, 1997a)-Dark gray to very dark gray, typically fine- to very fine-grained, argillaceous siliciclastic rocks, with common orange-brown weathering surfaces. Rocks have a better developed low-grade metamorphic fabric (phyllitic) compared to the Cretaceous to Jurassic age sandstone and shale lithologies above (map units 'KJwq', 'KJws').
    TrPpConglomerate (Triassic and Permian: Reifenstuhl and others, 1997a)-Very dark gray, orange-brown-weathering, matrix-supported, chert-pebble to cobble conglomerate. Matrix is dark gray argillite to very fine sand, and clasts are sub-rounded pebble to cobble size.
    MgGlobe quartzite unit (Mississippian: Weber and others, 1992; Mortensen and Thompson, 1990)-Light gray, light- to medium-gray weathering and iron-stained, fine- to medium-grained, bimodal to moderately sorted, distinctive vitreous quartzite, with interbedded medium to dark gray slate, phyllite, and shaley rocks. Framework grains are well rounded to sub-rounded monocrystalline quartz, and minor chert clasts.
    DlDevonian limestone fault slivers at Granite Creek [Famennian (late Late Devonian): this report]-Dark gray, light gray-weathering, lime mudstone. Uppermost strata of the largest fault sliver include abundant floating quartz grains up to 3 mm in diameter, which are increasingly abundant down-section.
    DcConglomerate (Late Devonian?: this report)-Dark gray to very dark gray, brown-weathering, clast-supported, chert-pebble to cobble conglomerate; matrix consists of siliciclastic and carbonate material, and clasts are sub-rounded pebble to cobble size.
    PzlcaChert and cherty argillite (Ordovician)-Heterogeneous unit composed dominantly of light gray to gray, thinly laminated, recrystallized sericitic chert and siliceous argillite, commonly with phyllitic argillite partings; 'cherty argillite' typically has cherty or mylonitic aspect on weathered surfaces, but fine-grained elastic or recrystallized texture on fresh surfaces.
    PzlvVolcanic unit (Ordovician)-Greenish-gray, chloritic and feldspathic rocks and greenstone. Protolith of volcanic rocks is volcaniclastic, tuffaceous, and flow rocks of basaltic to intermediate composition. Some rocks are diabasic and may be meta-intrusive rocks; the number of metavolcanic layers is uncertain.
    PzloOrum limestone (Middle Ordovician to Neoproterozoic: informal name, Hopkins and Taber, unpublished manuscript)-Light to medium gray, tan to reddish brown-weathering, extensively recrystallized, typically thin- to medium-bedded lime mudstone. Unit is locally thick-bedded, and locally includes ooid grainstones and cryptalgal lamination.
    OfcFossil Creek volcanics (Late to Early Ordovician: Weber and others, 1992)-Heterogeneous assemblage of basalt, agglomerate, volcaniclastic conglomerate, lime wackestone, calcareous feldspathic sandstone, shale, siltstone, chert, slate, and phyllite.
    PzPadDolostone and limestone-White to light gray, massive-bedded, locally laminated, siliceous dolostone and medium gray to dark gray lime mudstone, in approximately equal amounts. Dolostone is typically extensively silicified and characterized by box-work silica network.
    PzPagGreenstone-Dark greenish gray, massive to well foliated, locally magnetic greenstone, amygdaloidal greenstone, and agglomeratic greenstone; basaltic to intermediate composition. Contains calcite amygdule fillings, locally abundant pyrite cubes, and slightly stretched volcanic and carbonate clasts up to cobble size.
    PzPacCherty argillite and chert-Heterogeneous unit of dominantly black to dark gray chert and siliceous to carbonaceous argillite with well developed phyllitic to subphyllitic slate-like cleavage, and containing one or more dark gray limestone layers or lenses. The geochemical signature of this unit is typical of the chert in the Amy Creek unit (Haug and others, 1997) of Weber and others (1988).
    PzPwgSiliciclastic rock-Medium gray, tan-weathering, thin-bedded, fine-grained argillaceous sandstone, siltstone, rare greenstone (?), and phyllitic argillite. Locally, these rocks include up to 30 percent calcite that likely represents recrystallized matrix. Black, non-calcareous, carbonaceous, phyllitic argillite interbeds and partings are common.
    TgHot Springs granite pluton (58 Ma) - Medium- to coarse-grained biotite granite and rare tourmaline-biotite granite. Outcrops as subdued, blocky rubble or a brown gruss. The dominant textural variety contains coarse-grained potassium feldspar (30 percent) in a matrix of medium-grained smoky quartz (30 percent), albitic plagioclase (30 percent), and slightly chloritized biotite (10 percent).
    KmzdMonzodiorite- Black and white 'peppered', medium-grained, subequigranular, alkalic plutonic rock lacking quartz and with more plagioclase than alkali feldspar. Mafic minerals (clinopyroxene > biotite > hornblende) commonly make up more than 50 percent of the rock.
    JRcCarbonatite - (approximately 200 Ma) Medium- to coarse-grained, dolomite-calcite-magnetite-apatite-rich rock, which weathers to a deep red gossan and is characterized by an intense magnetic high. Occurs as two steeply dipping sills (?) up to 30 m thick, which may be a single sill or dike that is repeated by isoclinal folding.

    SUNIT
    Surficial geologic map unit labels (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    bExposed bedrock- bedrock with essentially no cover
    bcThinly covered bedrock - bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris
    QafAlluvial fan deposits - Fan-shaped, heterogeneous mixtures of gravel with some sand and silt and few to numerous, subangular to rounded boulders, especially in proximal areas; clasts locally derived; may include debris-flow deposits; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels; locally covered by reworked silt.
    QaAlluvium in modern stream channels - Elongated deposits of stratified gravel and sand with few to numerous boulders underlying active streams, flood plains, and associated low terraces; well sorted and medium to thick bedded, locally cross-bedded; shows fining-upward cycles.
    QapAlluvial plain deposits - Irregular blankets and low-angle fans of stratified gravel and sand with silt interbeds and few to numerous boulders underlying much of Baker Creek flats; well sorted and medium to thick bedded, locally cross-bedded; surface flat to gently sloping with numerous shallow, interconnected channels.
    QasSilty alluvium in modern stream channels - Irregular, elongated deposits of stratified silt beneath modern channels and flood plains of streams draining loess-mantled slopes; may include fine-grained debris flow deposits, especially in the upper reaches; moderately to well sorted and medium to thin bedded, locally cross-bedded.
    QfpFlood plain alluvium bordering modern streams - Elongated deposits of stratified pebble-cobble gravel and medium sand with few to numerous boulders forming modern flood plains and associated low (~3 m) terraces; typically mantled by thin layer of silty over-bank deposits
    QsfSilt fan deposits - Fan-shaped deposits of dark brown to gray silt with some sand and angular to subrounded pebbles in proximal areas; may include fine-grained debris flow deposits, especially in the upper reaches; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels
    QagOld, high-level alluvial gravels - Irregular residual deposits of gold-bearing, pebble-cobble gravel with well rounded quartzite boulders up to 3 m diameter preserved on high interfluves in the Eureka Creek area; up to 4 m thick, but generally much thinner; locally extensively reworked by mining activity
    QacUndifferentiated alluvial and colluvial valley-fill deposits - Fan-shaped and elongated heterogeneous mixtures of subangular rock fragments and gravel with some silt and sand deposited in upper stream courses primarily by brief, intense summer stream flow, debris flows, and gelifluction; surface smooth, except for local low scarps and shallow, steep-sided channels.
    QcUndifferentiated colluvium - Irregular, heterogeneous blankets, aprons, and fans of angular to subrounded rock fragments, gravel, sand, and silt that are left on slopes, slope bases, or high-level surfaces by residual weathering and complex mass-movement processes, including rolling, sliding, flowing, gelifluction, and frost creep
    QcaColluvial apron and fan deposits - Apron- and fan-shaped, heterogeneous mixtures of angular rock fragments with trace to some gravel, sand, and silt deposited at the bases of steep walls of modern stream valleys; may include or be capped by a considerable amount of redeposited eolian silt; locally washed by meltwater and slope runoff; surface steep to gently sloping.
    QelLoess - Homogeneous blankets of well sorted, mottled, light grayish-brown silt deposited by eolian processes; generally structureless, but with broadly horizontal bedding and some laminations, wavy bedding, and small-scale cross-bedding; contains scattered small charcoal fragments and root casts; local cryoturbation structures
    QelpPitted loess - Homogeneous blankets of mottled, light grayish-brown silt and organic silt deposited by eolian processes and subsequently modified by melting of ice-rich permafrost; generally massive to locally bedded
    QerReworked upland silt - Heterogeneous blankets of silt and organic silt originally laid down by eolian processes and subsequent minor to extensive reworking by fluvial and colluvial processes; includes silt-rich debris-flow deposits; may contain angular clasts of local origin; massive to thinly bedded, with some wavy bedding and cross-bedding; commonly perennially frozen and ice rich
    QldDelta deposits - Fan-shaped, heterogeneous mixture of well sorted silt, sand, and gravel; thick to thin bedded; shows cross-bedding and fining-upward cycles; surface smooth, except for numerous shallow, interconnected channels.
    QsSwamp deposits - Semicircular to irregular deposits of silt and peat in poorly drained areas; saturated and locally frozen below a depth of about 1 m, locally ice rich; surface flat and smooth, may have standing water.
    QmtMine tailings - Water-washed pebble-cobble gravel with trace to some sand reworked by placer mining operations; typically well sorted; surface irregular or forming symmetrical ridges and cones.
    WATERbody of water

    UNIT
    Generic geologic map unit labels (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    KwcvWilber Creek unit siliciclastic and volcaniclastic rocks (late Albian(?): Weber and others, 1992) - Very dark gray to dark greenish dark gray, volcanic clast-bearing, poorly sorted, sub-angular, medium- to coarse-grained, marine, argillaceous lithic sandstone, shale and siltstone. Estimates of the framework grain composition are: 55 percent chert, 25 percent quartz, 15 percent plagioclase (which includes about 5 percent obvious volcanic clasts), and 5 percent sedimentary and metamorphic rock fragments, and minor white mica.
    KwcsWilber Creek unit sandstone, shale, siltstone, undivided (Albian: Weber and others, 1992) - Very dark gray to dark greenish gray, poorly sorted, marine, argillaceous lithic sandstone, shale, and siltstone containing white mica-bearing argillaceous sandstone as laminae and thin interbeds; rare conglomerate. Beds are typically thin, parallel, laterally continuous, sharp-based, and graded; from fine to medium grained at the base, grading up to silt at the top of beds.
    KJwqWolverine quartzite unit (Early Cretaceous and Late Jurassic: Weber and others, 1992) - Very light gray to tan, white- to medium gray-weathering, moderately well sorted, subrounded, fine- to medium-grained quartzite, and sublitharenite with interbedded shaley rocks. Estimates of sandstone clast composition indicate greater than 90 percent quartz (rare light-blue color), two to five percent chert, and locally trace amounts of feldspar and white mica.
    KJwsWolverine quartzite unit sandstone and shale-undivided (Early Cretaceous and Late Jurassic: Weber and others, 1992) - Medium gray to light gray, locally black, lichen-covered, quartz-rich sandstone and interbedded shale. Sandstone is silica-cemented, well-indurated quartzarenite but lacks the prominent outcrop pattern, continuity, and thickness of the quartzite unit (map unit 'KJwq').
    TrPs***Note: typographical error exists on the Preliminary Geologic Map of the Tanana A-1 and A-2 Quadrangles, Central Alaska (Publication PDF98-37A-SH1). Unit TrPa does not exist. Unit label should read TrPs.*** Argillite, sandstone and shale (Triassic and Permian: Reifenstuhl and others, 1997a) - Dark gray to very dark gray, typically fine to very fine grained, argillaceous siliciclastic rocks, with common orange-brown weathering surfaces. Rocks have a better developed low-grade metamorphic fabric (phyllitic) compared to the Cretaceous to Jurassic age sandstone and shale lithologies above (map units 'KJwq', 'KJws').
    TrPpConglomerate (Triassic and Permian: Reifenstuhl and others, 1997a) - Very dark gray, orange-brown-weathering, matrix-supported, chert-pebble to cobble conglomerate. Matrix is dark gray argillite to very fine sand, and clasts are sub-rounded pebble to cobble size.
    MgGlobe quartzite unit (Mississippian: Weber and others, 1992; Mortensen and Thompson, 1990) - Light gray, light- to medium-gray weathering and iron-stained, fine to medium-grained, bimodal to moderately sorted, distinctive vitreous quartzite, with interbedded medium to dark gray slate, phyllite, and shaley rocks. Framework grains are well rounded to subrounded monocrystalline quartz, and minor chert clasts.
    DlDevonian limestone fault slivers at Granite Creek [Famennian (late Late Devonian): this report] - Dark gray, light gray-weathering, lime mudstone. Uppermost strata of the largest fault sliver include abundant floating quartz grains up to 3 mm in diameter, which are increasingly abundant down-section.
    DcConglomerate (Late Devonian?: this report) - Dark gray to very dark gray, brown-weathering, clast-supported, chert-pebble to cobble conglomerate; matrix consists of siliciclastic and carbonate material, and clasts are sub-rounded pebble to cobble size.
    PzlcaChert and cherty argillite (Ordovician) - Heterogeneous unit composed dominantly of light gray to gray, thinly laminated, recrystallized sericitic chert and siliceous argillite, commonly with phyllitic argillite partings; 'cherty argillite' typically has cherty or mylonitic aspect on weathered surfaces, but fine-grained elastic or recrystallized texture on fresh surfaces.
    PzlvVolcanic unit (Ordovician) - Greenish-gray, chloritic and feldspathic rocks and greenstone. Protolith of volcanic rocks is volcaniclastic, tuffaceous, and flow rocks of basaltic to intermediate composition. Some rocks are diabasic and may be meta-intrusive rocks; the number of metavolcanic layers uncertain.
    PzloOrum limestone (Middle Ordovician to Neoproterozoic: informal name, Hopkins and Taber, unpublished manuscript) - Light to medium gray, tan to reddish brown-weathering, extensively recrystallized, typically thin- to medium-bedded lime mudstone. Unit is locally thick-bedded, and locally includes ooid grainstones and cryptalgal lamination.
    OfcFossil Creek volcanics (Late to Early Ordovician: Weber and others, 1992) - Heterogeneous assemblage of basalt, agglomerate, volcaniclastic conglomerate, lime wackestone, calcareous feldspathic sandstone, shale, siltstone, chert, slate, and phyllite.
    PzPadDolostone and limestone - White to light gray, massive-bedded, locally laminated, siliceous dolostone and medium gray to dark gray lime mudstone, in approximately equal amounts. Dolostone is typically extensively silicified and characterized by box-work silica network.
    PzPagGreenstone - Dark greenish gray, massive to well-foliated, locally magnetic greenstone, amygdaloidal greenstone, and agglomeratic greenstone; basaltic to intermediate composition. Contains calcite amygdule fillings, locally abundant pyrite cubes, and slightly stretched volcanic and carbonate clasts up to cobble size.
    PzPacCherty argillite and chert - Heterogeneous unit of dominantly black to dark gray chert and siliceous to carbonaceous argillite with well-developed phyllitic to subphyllitic slate-like cleavage, and containing one or more dark gray limestone layers or lenses. The geochemical signature of this unit is typical of the chert in the Amy Creek unit (Haug and others, 1997) of Weber and others (1988).
    PzPwgSiliciclastic rock - Medium gray, tan-weathering, thin-bedded, fine-grained argillaceous sandstone, siltstone, rare greenstone (?), and phyllitic argillite. Locally, these rocks include up to 30 percent calcite that likely represents recrystallized matrix. Black, non-calcareous, carbonaceous, phyllitic argillite interbeds and partings are common.
    TgHot Springs granite pluton (58 Ma) - Medium- to coarse-grained biotite granite and rare tourmaline-biotite granite. Outcrops as subdued, blocky rubble or a brown gruss. The dominant textural variety contains coarse-grained potassium feldspar (30 percent) in a matrix of medium-grained smoky quartz (30 percent), albitic plagioclase (30 percent), and slightly chloritized biotite (10 percent).
    KmzdMonzodiorite - Black and white 'peppered,' medium-grained, subequigranular, alkalic plutonic rock lacking quartz and with more plagioclase than alkali feldspar. Mafic minerals (clinopyroxene > biotite > hornblende) commonly make up more than 50 percent of the rock.
    QafAlluvial fan deposits - Fan-shaped, heterogeneous mixtures of gravel with some sand and silt and few to numerous, subangular to rounded boulders, especially in proximal areas; clasts locally derived; may include debris-flow deposits; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels; locally covered by reworked silt.
    QaAlluvium in modern stream channels - Elongated deposits of stratified gravel and sand with few to numerous boulders underlying active streams, flood plains, and associated low terraces; well sorted and medium to thick bedded, locally cross-bedded; shows fining-upward cycles.
    QapAlluvial plain deposits - Irregular blankets and low-angle fans of stratified gravel and sand with silt interbeds and few to numerous boulders underlying much of Baker Creek flats; well sorted and medium to thick bedded, locally cross-bedded; surface flat to gently sloping with numerous shallow, interconnected channels
    QasSilty alluvium in modern stream channels - Irregular, elongated deposits of stratified silt beneath modern channels and flood plains of streams draining loess-mantled slopes; may include fine-grained debris flow deposits, especially in the upper reaches; moderately to well sorted and medium to thin bedded, locally cross-bedded.
    QfpFloodplain alluvium bordering modern streams - Elongated deposits of stratified pebble-cobble gravel and medium sand with few to numerous boulders forming modern flood plains and associated low (~3 m) terraces; typically mantled by thin layer of silty over-bank deposits
    QsfSilt fan deposits - Fan-shaped deposits of dark brown to gray silt with some sand and angular to subrounded pebbles in proximal areas; may include fine-grained debris flow deposits, especially in the upper reaches; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels
    QagOld, high-level alluvial gravels - Irregular residual deposits of gold-bearing, pebble-cobble gravel with well rounded quartzite boulders up to 3 m diameter preserved on high interfluves in the Eureka Creek area; up to 4 m thick, but generally much thinner; locally extensively reworked by mining activity
    QacUndifferentiated alluvial and colluvial valley-fill deposits - Fan-shaped and elongated heterogeneous mixtures of subangular rock fragments and gravel with some silt and sand deposited in upper stream courses primarily by brief, intense summer stream flow, debris flows, and gelifluction; surface smooth, except for local low scarps and shallow, steep-sided channels.
    QcUndifferentiated colluvium - Irregular, heterogeneous blankets, aprons, and fans of angular to subrounded rock fragments, gravel, sand, and silt that are left on slopes, slope bases, or high-level surfaces by residual weathering and complex mass-movement processes, including rolling, sliding, flowing, gelifluction, and frost creep
    QcaColluvial apron and fan deposits - Apron- and fan-shaped, heterogeneous mixtures of angular rock fragments with trace to some gravel, sand, and silt deposited at the bases of steep walls of modern stream valleys; may include or be capped by a considerable amount of redeposited eolian silt; locally washed by meltwater and slope runoff; surface steep to gently sloping.
    QelLoess - Homogeneous blankets of well-sorted, mottled, light grayish-brown silt deposited by eolian processes; generally structureless, but with broadly horizontal bedding and some laminations, wavy bedding, and small-scale cross-bedding; contains scattered small charcoal fragments and root casts; local cryoturbation structures
    QelpPitted loess - Homogeneous blankets of mottled, light grayish-brown silt and organic silt deposited by eolian processes and subsequently modified by melting of ice-rich permafrost; generally massive to locally bedded
    QerReworked upland silt - Heterogeneous blankets of silt and organic silt originally laid down by eolian processes and subsequent minor to extensive reworking by fluvial and colluvial processes; includes silt-rich debris-flow deposits; may contain angular clasts of local origin; massive to thinly bedded, with some wavy bedding and cross-bedding; commonly perennially frozen and ice rich
    QldDelta deposits - Fan-shaped, heterogeneous mixture of well sorted silt, sand, and gravel; thick to thin bedded; shows cross-bedding and fining-upward cycles; surface smooth, except for numerous shallow, interconnected channels.
    QsSwamp deposits - Semicircular to irregular deposits of silt and peat in poorly drained areas; saturated and locally frozen below a depth of about 1 m, locally ice rich; surface flat and smooth, may have standing water.
    QmtMine tailings - Water-washed pebble-cobble gravel with trace to some sand reworked by placer mining operations; typically well sorted; surface irregular or forming symmetrical ridges and cones.
    WATERbody of water

    MAT
    Preliminary engineering-geologic map unit labels (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    GSFluvial and glaciofluvial gravel, sand, and silt. Chiefly (estimated >80 percent) clean sand and gravel. Grain size, sorting, and degree of stratification are variable. Permafrost may be present, especially in older deposits. Component geologic units include Qa, Qag, Qap, Qfp, and Qmt. Source of geologic units: Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Pinney, D.S., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Alaska Division of Geological & Geophysical Surveys Public Data File 98-37A.
    GMPoorly to moderately well-sorted clay, silt, sand, gravel, and diamicton of colluvial and fluvial origins. Includes angular, unsorted talus debris and chaotically deformed colluvium derived from landslides. Component geologic units include Qac, Qaf, Qc, and Qca. Source of geologic units: Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Pinney, D.S., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Alaska Division of Geological & Geophysical Surveys Public Data File 98-37A.
    SMSilt deposited primarily by wind and reworked by fluvial and colluvial processes. May be organic-rich. Commonly frozen and ice-rich, especially on north-facing slopes. Chiefly fine materials. Component geologic units include Qas, Qel, Qelp, Qer, Qld, and Qsf. Source of geologic units: Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Pinney, D.S., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Alaska Division of Geological & Geophysical Surveys Public Data File 98-37A.
    OROrganic-rich silt and peat in bogs and thaw lake basins. Commonly frozen and ice-rich due to the excellent insulating properties of peat. Generally water-saturated. Component geologic units include Qs. Source of geologic units: Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Pinney, D.S., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Alaska Division of Geological & Geophysical Surveys Public Data File 98-37A.
    BCMedium-jointed, fine- to coarse-grained sedimentary carbonate rocks. Includes limestone, dolostone, and marble. Component geologic units include Dl, Pzlo, and PzPad. Source of geologic units: Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Pinney, D.S., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Alaska Division of Geological & Geophysical Surveys Public Data File 98-37A.
    BGCoarse-jointed, coarse-grained igneous lithologies. Chiefly granitic rocks. Component geologic units include Kgs, Kmo, Kmzd, Ksy, and Tg. Source of geologic units: Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Pinney, D.S., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Alaska Division of Geological & Geophysical Surveys Public Data File 98-37A.
    BMMedium-jointed, fine- to medium-grained quartzose sedimentary rocks. Includes quartzose sandstone and conglomerate, quartzite, chert, and hornfels. Component geologic units include Dc, KJwq, Kwcq, Mg, Pzlca, and TrPp. Source of geologic units: Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Pinney, D.S., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Alaska Division of Geological & Geophysical Surveys Public Data File 98-37A.
    BVMedium-jointed, fine-grained igneous rocks. Chiefly volcanic flow rock, dikes, and greenstone. Component geologic units include Kdm, Ofc, Pzlv, and PzPag. Source of geologic units: Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Pinney, D.S., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Alaska Division of Geological & Geophysical Surveys Public Data File 98-37A.
    BURocks of mixed lithology and very fine-grained sedimentary lithologies that are generally poorly suited for use as construction materials. Includes shale, siltstone, and argillite. Component geologic units include Kdm, Ofc, Pzlv, and PzPag. Source of geologic units: Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Pinney, D.S., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Alaska Division of Geological & Geophysical Surveys Public Data File 98-37A.
    H20body of water

    tana2comp_polygon.shp
    Object type is vector, there are 1,266 rows associated with this entity, and the entity values refer to comprehensive geologic polygons (Source: Alaska Division of Geological & Geophysical Surveys)

    BUNIT
    Interpretive geologic map unit labels (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    FZONEKaltag Fault Zone - Major dextral strike-slip fault zone connecting Tintina Fault Zone. The Kaltag fault zone is topographically subdued but cuts the Amy Creek dolomite unit and the Livengood Chert unit.
    KwcqWilber Creek unit quartzite (Albian: Weber and others, 1992) - Medium gray to light gray, highly quartzitic, hard, dense, argillaceous lithic quartzite. Quartzite interbeds occur locally as abundant laminae up to 20 cm thick in the Wilber Creek unit (map unit 'Kwcs') on the northern side of Manley Dome (where it is a mappable unit).
    KdmMafic dikes (95 Ma) - Very dark gray and greenish very dark gray, very fine grained hypabyssal dikes. Composition ranges from monzodiorite to monzonite, with little or no quartz, abundant clinopyroxene, and plagioclase subequal in abundance to alkali feldspar.
    KgsGranite and quartz syenite - Buff to light gray, fine to coarse grained, sub-equigranular, holocrystalline rock. The rock exhibits slight hydrothermal alteration, with feldspar partly converted to fine-grained white mica. Quartz/(quartz + total feldspar) ratios vary from 15 to 35 percent, and the bulk of the feldspar appears to be K-feldspar.
    KsySyenite and quartz syenite - Black and white-'peppered,' coarse to medium grained, subequigranular to trachytoid, syenite, and quartz syenite. With the exception of euhedral, megacrystic, alkali feldspar, the minerals are typically subhedral and anhedral.
    KmoMonzonite - Black and white 'peppered,' coarse to medium grained, locally foliated, subequigranular to trachytoid, porphyritic monzonite and quartz monzonite. Mineralogy is typically subhedral and anhedral, with the exception of euhedral megacrystic alkali feldspar.
    PzumUltramafic rocks (approximately 540 Ma) - Serpentinite, gabbro, and minor roddingite, which weather to a buff-colored massive rubble. Predominantly serpentinite, consisting of fine-grained, moderately foliated to unfoliated serpentine-talc with 2 to 5 percent fine- to medium-grained magnetite, 0 to 20 percent magnesite, 0 to 25 percent altered, medium-grained orthopyroxene, 0.1 to 0.5 percent fine- to medium-grained chromite, and 0 to 1 percent fine-grained chlorite.
    KwcvWilber Creek unit siliciclastic and volcaniclastic rocks (late Albian(?): Weber and others, 1992) - Very dark gray to dark greenish dark gray, volcanic clast-bearing, poorly sorted, sub-angular, medium- to coarse-grained, marine, argillaceous lithic sandstone, shale and siltstone. Estimates of the framework grain composition are 55 percent chert, 25 percent quartz, 15 percent plagioclase (which includes about 5 percent obvious volcanic clasts), and 5 percent sedimentary and metamorphic rock fragments, and minor white mica.
    KwcsWilber Creek unit sandstone, shale, siltstone, undivided (Albian: Weber and others, 1992) - Very dark gray to dark greenish gray, poorly sorted, marine, argillaceous lithic sandstone, shale, and siltstone containing white mica-bearing argillaceous sandstone as laminae and thin interbeds; rare conglomerate. Beds are typically thin, parallel, laterally continuous, sharp-based, and graded; from fine to medium grained at the base, grading up to silt at the top of beds.
    KJwqWolverine quartzite unit (Early Cretaceous and Late Jurassic: Weber and others, 1992) - Very light gray to tan, white- to medium gray-weathering, moderately well-sorted, subrounded, fine- to medium-grained quartzite, and sublitharenite with interbedded shaley rocks. Estimates of sandstone clast composition indicate greater than 90 percent quartz (rare light-blue color), two to five percent chert, and locally trace amounts of feldspar and white mica.
    KJwsWolverine quartzite unit sandstone and shale, undivided (Early Cretaceous and Late Jurassic: Weber and others, 1992) - Medium gray to light gray, locally black, lichen-covered, quartz-rich sandstone and interbedded shale. Sandstone is silica-cemented, well-indurated quartzarenite but lacks the prominent outcrop pattern, continuity, and thickness of the quartzite unit (map unit 'KJwq').
    TrPs***Note: typographical error exists on the Preliminary Geologic Map of the Tanana A-1 and A-2 Quadrangles, Central Alaska (Publication PDF98-37A-SH1). Unit TrPa does not exist. Unit label should read TrPs.*** Argillite, sandstone, and shale (Triassic and Permian: Reifenstuhl and others, 1997a) - Dark gray to very dark gray, typically fine to very fine grained, argillaceous siliciclastic rocks,with common orange-brown weathering surfaces. Rocks have a better developed low-grade metamorphic fabric (phyllitic) compared to the Cretaceous to Jurassic age sandstone and shale lithologies above (map units 'KJwq', 'KJws').
    TrPpConglomerate (Triassic and Permian: Reifenstuhl and others, 1997a) - Very dark gray, orange-brown-weathering, matrix-supported, chert-pebble to cobble conglomerate. Matrix is dark gray argillite to very fine sand, and clasts are sub-rounded pebble to cobble size.
    DcConglomerate (Late Devonian?: this report) - Dark gray to very dark gray, brown-weathering, clast-supported, chert-pebble to cobble conglomerate; matrix consists of siliciclastic and carbonate material, and clasts are sub-rounded pebble to cobble size.
    PzlcaChert and cherty argillite (Ordovician) - Heterogeneous unit composed dominantly of light gray to gray, thinly laminated, recrystallized sericitic chert and siliceous argillite, commonly with phyllitic argillite partings; 'cherty argillite' typically has cherty or mylonitic aspect on weathered surfaces, but fine-grained elastic or recrystallized texture on fresh surfaces.
    PzlvVolcanic unit (Ordovician) - Greenish-gray, chloritic and feldspathic rocks and greenstone. Protolith of volcanic rocks is volcaniclastic, tuffaceous, and flow rocks of basaltic to intermediate composition. Some rocks are diabasic and may be meta-intrusive rocks; the number of metavolcanic layers uncertain.
    PzloOrum limestone (Middle Ordovician to Neoproterozoic: informal name, Hopkins and Taber, unpublished manuscript) - Light to medium gray, tan to reddish brown-weathering, extensively recrystallized, typically thin- to medium-bedded lime mudstone. Unit is locally thick-bedded, and locally includes ooid grainstones and cryptalgal lamination.
    PzPadDolostone and limestone - White to light gray, massive-bedded, locally laminated, siliceous dolostone and medium gray to dark gray lime mudstone, in approximately equal amounts. Dolostone is typically extensively silicified and characterized by box-work silica network.
    PzPacCherty-argillite and chert - Heterogeneous unit of dominantly black to dark gray chert and siliceous to carbonaceous argillite with well-developed phyllitic to subphyllitic slate-like cleavage, and containing one or more dark gray limestone layers or lenses. The geochemical signature of this unit is typical of the chert in the Amy Creek unit (Haug and others, 1997) of Weber and others (1988).
    TgHot Springs granite pluton (58 Ma) - Medium- to coarse-grained biotite granite and rare tourmaline-biotite granite. Outcrops as subdued, blocky rubble or a brown gruss. The dominant textural variety contains coarse-grained potassium feldspar (30 percent) in a matrix of medium-grained smoky quartz (30 percent), albitic plagioclase (30 percent), and slightly chloritized biotite (10 percent).
    KmzdMonzodiorite - Black and white 'peppered,' medium grained, subequigranular, alkalic plutonic rock lacking quartz and with more plagioclase than alkali feldspar. Mafic minerals (clinopyroxene > biotite > hornblende) commonly make up more than 50 percent of the rock.
    JRcCarbonatite (approximately 200 Ma) - Medium to coarse grained, dolomite-calcite-magnetite-apatite-rich rock, which weathers to a deep red gossan and is characterized by an intense magnetic high. Occurs as two steeply dipping sills (?) up to 30 m thick, which may be a single sill or dike that is repeated by isoclinal folding.

    SUNIT
    Surficial geologic map unit labels (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    bExposed bedrock - Bedrock with essentially no cover
    bcThinly covered bedrock - Bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris
    QafAlluvial fan deposits - Fan-shaped, heterogeneous mixtures of gravel with some sand and silt and few to numerous, subangular to rounded boulders, especially in proximal areas; clasts locally derived; may include debris-flow deposits; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels; locally covered by reworked silt.
    QaAlluvium in modern stream channels - Elongated deposits of stratified gravel and sand with few to numerous boulders underlying active streams, flood plains, and associated low terraces; well sorted and medium to thick bedded, locally cross-bedded; shows fining-upward cycles.
    QapAlluvial plain deposits - Irregular blankets and low-angle fans of stratified gravel and sand with silt interbeds and few to numerous boulders underlying much of Baker Creek flats; well sorted and medium to thick bedded, locally cross-bedded; surface flat to gently sloping with numerous shallow, interconnected channels
    QasSilty alluvium in modern stream channels - Irregular, elongated deposits of stratified silt beneath modern channels and flood plains of streams draining loess-mantled slopes; may include fine-grained debris flow deposits, especially in the upper reaches; moderately to well sorted and medium to thin bedded, locally cross-bedded.
    QfpFloodplain alluvium bordering modern streams - Elongated deposits of stratified pebble-cobble gravel and medium sand with few to numerous boulders forming modern flood plains and associated low (~3 m) terraces; typically mantled by thin layer of silty over-bank deposits
    QsfSilt fan deposits - Fan-shaped deposits of dark brown to gray silt with some sand and angular to subrounded pebbles in proximal areas; may include fine-grained debris flow deposits, especially in the upper reaches; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels
    QacUndifferentiated alluvial and colluvial valley-fill deposits - Fan-shaped and elongated heterogeneous mixtures of subangular rock fragments and gravel with some silt and sand deposited in upper stream courses primarily by brief, intense summer stream flow, debris flows, and gelifluction; surface smooth, except for local low scarps and shallow, steep-sided channels.
    QcUndifferentiated colluvium - Irregular, heterogeneous blankets, aprons, and fans of angular to subrounded rock fragments, gravel, sand, and silt that are left on slopes, slope bases, or high-level surfaces by residual weathering and complex mass-movement processes, including rolling, sliding, flowing, gelifluction, and frost creep
    QcaColluvial apron and fan deposits - Apron- and fan-shaped, heterogeneous mixtures of angular rock fragments with trace to some gravel, sand, and silt deposited at the bases of steep walls of modern stream valleys; may include or be capped by a considerable amount of redeposited eolian silt; locally washed by meltwater and slope runoff; surface steep to gently sloping.
    QelLoess - Homogeneous blankets of well-sorted, mottled, light grayish-brown silt deposited by eolian processes; generally structureless, but with broadly horizontal bedding and some laminations, wavy bedding, and small-scale cross-bedding; contains scattered small charcoal fragments and root casts; local cryoturbation structures
    QelpPitted loess - Homogeneous blankets of mottled, light grayish-brown silt and organic silt deposited by eolian processes and subsequently modified by melting of ice-rich permafrost; generally massive to locally bedded
    QerReworked upland silt - Heterogeneous blankets of silt and organic silt originally laid down by eolian processes and subsequent minor to extensive reworking by fluvial and colluvial processes; includes silt-rich debris-flow deposits; may contain angular clasts of local origin; massive to thinly bedded, with some wavy bedding and cross-bedding; commonly perennially frozen and ice rich
    QsSwamp deposits - Semicircular to irregular deposits of silt and peat in poorly drained areas; saturated and locally frozen below a depth of about 1 m, locally ice rich; surface flat and smooth, may have standing water
    QmtMine tailings - Water-washed pebble-cobble gravel with trace to some sand reworked by placer mining operations; typically well sorted; surface irregular or forming symmetrical ridges and cones

    UNIT
    Generic geologic map unit labels (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    KwcsWilber Creek unit sandstone, shale, siltstone, undivided (Albian: Weber and others, 1992) - Very dark gray to dark greenish gray, poorly sorted, marine, argillaceous lithic sandstone, shale, and siltstone containing white mica-bearing argillaceous sandstone as laminae and thin interbeds; rare conglomerate. Beds are typically thin, parallel, laterally continuous, sharp-based, and graded; from fine to medium grained at the base, grading up to silt at the top of beds.
    KJwqWolverine quartzite unit (Early Cretaceous and Late Jurassic: Weber and others, 1992) - Very light gray to tan, white- to medium gray-weathering, moderately well-sorted, subrounded, fine- to medium-grained quartzite, and sublitharenite with interbedded shaley rocks. Estimates of sandstone clast composition indicate greater than 90 percent quartz (rare light-blue color), two to five percent chert, and locally trace amounts of feldspar and white mica.
    KJwsWolverine quartzite unit sandstone and shale, undivided (Early Cretaceous and Late Jurassic: Weber and others, 1992) - Medium gray to light gray, locally black, lichen-covered, quartz-rich sandstone and interbedded shale. Sandstone is silica-cemented, well-indurated quartzarenite but lacks the prominent outcrop pattern, continuity, and thickness of the quartzite unit (map unit 'KJwq').
    TrPs***Note: typographical error exists on the Preliminary Geologic Map of the Tanana A-1 and A-2 Quadrangles, Central Alaska (Publication PDF98-37A-SH1). Unit TrPa does not exist. Unit label should read TrPs.*** Argillite, sandstone and shale (Triassic and Permian: Reifenstuhl and others, 1997a) - Dark gray to very dark gray, typically fine to very fine grained, argillaceous siliciclastic rocks,with common orange-brown weathering surfaces. Rocks have a better developed low-grade metamorphic fabric (phyllitic) compared to the Cretaceous to Jurassic age sandstone and shale lithologies above (map units 'KJwq', 'KJws').
    TrPpConglomerate (Triassic and Permian: Reifenstuhl and others, 1997a) - Very dark gray, orange-brown weathering, matrix-supported, chert-pebble to cobble conglomerate. Matrix is dark gray argillite to very fine sand, and clasts are sub-rounded pebble to cobble size.
    DcConglomerate (Late Devonian?: this report) - Dark gray to very dark gray, brown-weathering, clast-supported, chert-pebble to cobble conglomerate; matrix consists of siliciclastic and carbonate material, and clasts are sub-rounded pebble to cobble size.
    PzlcaChert and cherty argillite (Ordovician) - Heterogeneous unit composed dominantly of light gray to gray, thinly laminated, recrystallized sericitic chert and siliceous argillite, commonly with phyllitic argillite partings; 'cherty argillite' typically has cherty or mylonitic aspect on weathered surfaces, but fine-grained elastic or recrystallized texture on fresh surfaces.
    PzlvVolcanic unit (Ordovician) - Greenish-gray, chloritic and feldspathic rocks and greenstone. Protolith of volcanic rocks is volcaniclastic, tuffaceous, and flow rocks of basaltic to intermediate composition. Some rocks are diabasic and may be meta-intrusive rocks; the number of metavolcanic layers uncertain.
    PzloOrum limestone (Middle Ordovician to Neoproterozoic: informal name, Hopkins and Taber, unpublished manuscript) - Light to medium gray, tan to reddish brown-weathering, extensively recrystallized, typically thin- to medium-bedded lime mudstone. Unit is locally thick-bedded, and locally includes ooid grainstones and cryptalgal lamination.
    PzPadDolostone and limestone - White to light gray, massive-bedded, locally laminated, siliceous dolostone and medium gray to dark gray lime mudstone, in approximately equal amounts. Dolostone is typically extensively silicified and characterized by box-work silica network.
    PzPacCherty-argillite and chert - Heterogeneous unit of dominantly black to dark gray chert and siliceous to carbonaceous argillite with well-developed phyllitic to subphyllitic slate-like cleavage, and containing one or more dark gray limestone layers or lenses. The geochemical signature of this unit is typical of the chert in the Amy Creek unit (Haug and others, 1997) of Weber and others (1988).
    TgHot Springs granite pluton (58 Ma) - Medium- to coarse-grained biotite granite and rare tourmaline-biotite granite. Outcrops as subdued, blocky rubble or a brown gruss. The dominant textural variety contains coarse-grained potassium feldspar (30 percent) in a matrix of medium-grained smoky quartz (30 percent), albitic plagioclase (30 percent), and slightly chloritized biotite (10 percent).
    KmzdMonzodiorite- Black and white 'peppered,' medium grained, subequigranular, alkalic plutonic rock lacking quartz and with more plagioclase than alkali feldspar. Mafic minerals (clinopyroxene > biotite > hornblende) commonly make up more than 50 percent of the rock.
    QafAlluvial fan deposits - Fan-shaped, heterogeneous mixtures of gravel with some sand and silt and few to numerous, subangular to rounded boulders, especially in proximal areas; clasts locally derived; may include debris-flow deposits; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels; locally covered by reworked silt.
    QaAlluvium in modern stream channels - Elongated deposits of stratified gravel and sand with few to numerous boulders underlying active streams, flood plains, and associated low terraces; well sorted and medium to thick bedded, locally cross-bedded; shows fining-upward cycles.
    QapAlluvial plain deposits - Irregular blankets and low-angle fans of stratified gravel and sand with silt interbeds and few to numerous boulders underlying much of Baker Creek flats; well sorted and medium to thick bedded, locally cross-bedded; surface flat to gently sloping with numerous shallow, interconnected channels
    QasSilty alluvium in modern stream channels - Irregular, elongated deposits of stratified silt beneath modern channels and flood plains of streams draining loess-mantled slopes; may include fine-grained debris flow deposits, especially in the upper reaches; moderately to well sorted and medium to thin bedded, locally cross-bedded.
    QfpFloodplain alluvium bordering modern streams - Elongated deposits of stratified pebble-cobble gravel and medium sand with few to numerous boulders forming modern flood plains and associated low (~3 m) terraces; typically mantled by thin layer of silty over-bank deposits
    QsfSilt fan deposits - Fan-shaped deposits of dark brown to gray silt with some sand and angular to subrounded pebbles in proximal areas; may include fine-grained debris flow deposits, especially in the upper reaches; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels
    QacUndifferentiated alluvial and colluvial valley-fill deposits - Fan-shaped and elongated heterogeneous mixtures of subangular rock fragments and gravel with some silt and sand deposited in upper stream courses primarily by brief, intense summer stream flow, debris flows, and gelifluction; surface smooth, except for local low scarps and shallow, steep-sided channels.
    QcUndifferentiated colluvium - Irregular, heterogeneous blankets, aprons, and fans of angular to subrounded rock fragments, gravel, sand, and silt that are left on slopes, slope bases, or high-level surfaces by residual weathering and complex mass-movement processes, including rolling, sliding, flowing, gelifluction, and frost creep
    QcaColluvial apron and fan deposits - Apron- and fan-shaped, heterogeneous mixtures of angular rock fragments with trace to some gravel, sand, and silt deposited at the bases of steep walls of modern stream valleys; may include or be capped by a considerable amount of redeposited eolian silt; locally washed by meltwater and slope runoff; surface steep to gently sloping.
    QelLoess - Homogeneous blankets of well-sorted, mottled, light grayish-brown silt deposited by eolian processes; generally structureless, but with broadly horizontal bedding and some laminations, wavy bedding, and small-scale cross-bedding; contains scattered small charcoal fragments and root casts; local cryoturbation structures
    QelpPitted loess - Homogeneous blankets of mottled, light grayish-brown silt and organic silt deposited by eolian processes and subsequently modified by melting of ice-rich permafrost; generally massive to locally bedded
    QerReworked upland silt - Heterogeneous blankets of silt and organic silt originally laid down by eolian processes and subsequent minor to extensive reworking by fluvial and colluvial processes; includes silt-rich debris-flow deposits; may contain angular clasts of local origin; massive to thinly bedded, with some wavy bedding and cross-bedding; commonly perennially frozen and ice rich
    QsSwamp deposits - Semicircular to irregular deposits of silt and peat in poorly-drained areas; saturated and locally frozen below a depth of about 1 m, locally ice rich; surface flat and smooth, may have standing water.
    QmtMine tailings - Water-washed pebble-cobble gravel with trace to some sand reworked by placer mining operations; typically well sorted; surface irregular or forming symmetrical ridges and cones.
    KwcqWilber Creek unit quartzite (Albian: Weber and others, 1992) - Medium to light gray, highly quartzitic, hard, dense, argillaceous lithic quartzite. Quartzite interbeds occur locally as abundant laminae up to 20 cm thick in the Wilber Creek unit (map unit 'Kwcs') on the northern side of Manley Dome (where it is a mappable unit).
    KdmMafic dikes (95 Ma) - Very dark gray and greenish very dark gray, very fine grained hypabyssal dikes. Composition ranges from monzodiorite to monzonite, with little or no quartz, abundant clinopyroxene, and plagioclase subequal in abundance to alkali feldspar.
    KgsGranite and quartz syenite - Buff to light gray, fine to coarse grained, sub-equigranular, holocrystalline rock. The rock exhibits slight hydrothermal alteration, with feldspar partly converted to fine-grained white mica. Quartz/(quartz + total feldspar) ratios vary from 15 to 35 percent, and the bulk of the feldspar appears to be K-feldspar.
    KsySyenite and quartz syenite - Black and white-'peppered,' coarse to medium grained, subequigranular to trachytoid, syenite and quartz syenite. With the exception of euhedral, megacrystic, alkali feldspar, the minerals are typically subhedral and anhedral.
    KmoMonzonite - Black and white 'peppered,' coarse to medium grained, locally foliated, subequigranular to trachytoid, porphyritic monzonite and quartz monzonite. Mineralogy is typically subhedral and anhedral, with the exception of euhedral megacrystic alkali feldspar.
    PzumUltramafic rocks (approximately 540 Ma) - Serpentinite, gabbro, and minor roddingite, which weather to a buff-colored massive rubble. Predominantly serpentinite, consisting of fine-grained, moderately foliated to unfoliated serpentine-talc with 2 to 5 percent fine- to medium-grained magnetite, 0 to 20 percent magnesite, 0 to 25 percent altered, medium-grained orthopyroxene, 0.1 to 0.5 percent fine- to medium-grained chromite, and 0 to 1 percent fine-grained chlorite.
    JRcCarbonatite (approximately 200 Ma) - Medium to coarse grained, dolomite-calcite-magnetite-apatite-rich rock, which weathers to a deep red gossan and is characterized by an intense magnetic high. Occurs as two steeply-dipping sills (?) up to 30 m thick, which may be a single sill or dike that is repeated by isoclinal folding.

    MAT
    Preliminary engineering-geologic map unit labels (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    GSFluvial and glaciofluvial gravel, sand, and silt. Chiefly (estimated >80 percent) clean sand and gravel. Grain size, sorting and degree of stratification are variable. Permafrost may be present, especially in older deposits. Component geologic units include Qa, Qag, Qap, Qfp, and Qmt. Source of geologic units: Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Pinney, D.S., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Alaska Division of Geological & Geophysical Surveys Public Data File 98-37A.
    GMPoorly- to moderately well-sorted clay, silt, sand, gravel, and diamicton of colluvial and fluvial origins. Includes angular, unsorted talus debris and chaotically deformed colluvium derived from landslides. Component geologic units include Qac, Qaf, Qc, and Qca. Source of geologic units: Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Pinney, D.S., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Alaska Division of Geological & Geophysical Surveys Public Data File 98-37A.
    SMSilt deposited primarily by wind and reworked by fluvial and colluvial processes. May be organic-rich. Commonly frozen and ice-rich, especially on north-facing slopes. Chiefly fine materials. Component geologic units include Qas, Qel, Qelp, Qer, Qld, and Qsf. Source of geologic units: Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Pinney, D.S., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Alaska Division of Geological & Geophysical Surveys Public Data File 98-37A.
    OROrganic-rich silt and peat in bogs and thaw lake basins. Commonly frozen and ice-rich due to the excellent insulating properties of peat. Generally water-saturated. Component geologic units include Qs. Source of geologic units: Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Pinney, D.S., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Alaska Division of Geological & Geophysical Surveys Public Data File 98-37A.
    BCMedium-jointed, fine- to coarse-grained sedimentary carbonate rocks. Includes limestone, dolostone, and marble. Component geologic units include Dl, Pzlo, and PzPad. Source of geologic units: Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Pinney, D.S., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Alaska Division of Geological & Geophysical Surveys Public Data File 98-37A.
    BGCoarse-jointed, coarse-grained igneous lithologies. Chiefly granitic rocks. Component geologic units include Kgs, Kmo, Kmzd, Ksy, and Tg. Source of geologic units: Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Pinney, D.S., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Alaska Division of Geological & Geophysical Surveys Public Data File 98-37A.
    BMMedium-jointed, fine- to medium-grained quartzose sedimentary rocks. Includes quartzose sandstone and conglomerate, quartzite, chert, and hornfels. Component geologic units include Dc, KJwq, Kwcq, Mg, Pzlca, and TrPp. Source of geologic units: Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Pinney, D.S., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Alaska Division of Geological & Geophysical Surveys Public Data File 98-37A.
    BORocks of lithologies not listed in other materials classes, but which may be suited for use as construction materials or for other specialized purposes. Includes carbonatite and ultramafic rocks. Component geologic units include JRc and Pzum. Source of geologic units: Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Pinney, D.S., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Alaska Division of Geological & Geophysical Surveys Public Data File 98-37A.
    BVMedium-jointed, fine-grained igneous rocks. Chiefly volcanic flow rock, dikes, and greenstone. Component geologic units include Kdm, Ofc, Pzlv, and PzPag. Source of geologic units: Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Pinney, D.S., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Alaska Division of Geological & Geophysical Surveys Public Data File 98-37A.
    BURocks of mixed lithology and very fine-grained sedimentary lithologies that are generally poorly suited for use as construction materials. Includes shale, siltstone, and argillite. Component geologic units include Kdm, Ofc, Pzlv, and PzPag. Source of geologic units: Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Pinney, D.S., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Alaska Division of Geological & Geophysical Surveys Public Data File 98-37A.

    hflsa1_comp_polygon.shp
    Object type is vector, there are 497 rows associated with this entity, and the entity values refer to comprehensive geologic polygons (Source: Alaska Division of Geological & Geophysical Surveys)

    SUNIT
    Surficial geologic map unit labels (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    bExposed bedrock - bedrock with essentially no cover
    bcThinly covered bedrock - bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris
    QafAlluvial fan deposits - Fan-shaped, heterogeneous mixtures of gravel with some sand and silt and few to numerous, subangular to rounded boulders, especially in proximal areas; clasts locally derived; may include debris-flow deposits; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels; locally covered by reworked silt.
    QaAlluvium in modern stream channels - Elongated deposits of stratified gravel and sand with few to numerous boulders underlying active streams, flood plains, and associated low terraces; well sorted and medium to thick bedded, locally cross-bedded; shows fining-upward cycles.
    QapAlluvial plain deposits - Irregular blankets and low-angle fans of stratified gravel and sand with silt interbeds and few to numerous boulders underlying much of Baker Creek flats; well sorted and medium to thick bedded, locally cross-bedded; surface flat to gently sloping with numerous shallow, interconnected channels
    QasSilty alluvium in modern stream channels - Irregular, elongated deposits of stratified silt beneath modern channels and flood plains of streams draining loess-mantled slopes; may include fine-grained debris flow deposits, especially in the upper reaches; moderately to well sorted and medium to thin bedded, locally cross-bedded.
    QfpFloodplain alluvium bordering modern streams - Elongated deposits of stratified pebble-cobble gravel and medium sand with few to numerous boulders forming modern flood plains and associated low (~3 m) terraces; typically mantled by thin layer of silty over-bank deposits
    QsfSilt fan deposits - Fan-shaped deposits of dark brown to gray silt with some sand and angular to subrounded pebbles in proximal areas; may include fine-grained debris flow deposits, especially in the upper reaches; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels
    QagOld, high-level alluvial gravels - Irregular residual deposits of gold-bearing, pebble-cobble gravel with well rounded quartzite boulders up to 3 m diameter preserved on high interfluves in the Eureka Creek area; up to 4 m thick, but generally much thinner; locally extensively reworked by mining activity
    QacUndifferentiated alluvial and colluvial valley-fill deposits - Fan-shaped and elongated heterogeneous mixtures of subangular rock fragments and gravel with some silt and sand deposited in upper stream courses primarily by brief, intense summer stream flow, debris flows, and gelifluction; surface smooth, except for local low scarps and shallow, steep-sided channels.
    QcUndifferentiated colluvium - Irregular, heterogeneous blankets, aprons, and fans of angular to subrounded rock fragments, gravel, sand, and silt that are left on slopes, slope bases, or high-level surfaces by residual weathering and complex mass-movement processes, including rolling, sliding, flowing, gelifluction, and frost creep
    QcaColluvial apron and fan deposits - Apron- and fan-shaped, heterogeneous mixtures of angular rock fragments with trace to some gravel, sand, and silt deposited at the bases of steep walls of modern stream valleys; may include or be capped by a considerable amount of redeposited eolian silt; locally washed by meltwater and slope runoff; surface steep to gently sloping.
    QelLoess - Homogeneous blankets of well-sorted, mottled, light grayish-brown silt deposited by eolian processes; generally structureless, but with broadly horizontal bedding and some laminations, wavy bedding, and small-scale cross-bedding; contains scattered small charcoal fragments and root casts; local cryoturbation structures
    QelpPitted loess - Homogeneous blankets of mottled, light grayish-brown silt and organic silt deposited by eolian processes and subsequently modified by melting of ice-rich permafrost; generally massive to locally bedded
    QerReworked upland silt - Heterogeneous blankets of silt and organic silt originally laid down by eolian processes and subsequent minor to extensive reworking by fluvial and colluvial processes; includes silt-rich debris-flow deposits; may contain angular clasts of local origin; massive to thinly bedded, with some wavy bedding and cross-bedding; commonly perennially frozen and ice rich
    QldDelta deposits - Fan-shaped, heterogeneous mixture of well sorted silt, sand, and gravel; thick to thin bedded; shows cross-bedding and fining-upward cycles; surface smooth, except for numerous shallow, interconnected channels.
    QsSwamp deposits - Semicircular to irregular deposits of silt and peat in poorly-drained areas; saturated and locally frozen below a depth of about 1 m, locally ice rich; surface flat and smooth, may have standing water.
    QmtMine tailings - Water-washed pebble-cobble gravel with trace to some sand reworked by placer mining operations; typically well sorted; surface irregular or forming symmetrical ridges and cones.
    nmNot mapped, body of water, region is irrelevant and not meaningful for the particular data layer. : the polygon having the software-defined attribute/column FID whose value is 451 represents Baker Lake. The annotation "Baker Lake", as seen on the Preliminary Geologic Map of the Tanana A-1 and A-2 Quadrangles, Central Alaska (Publication PDF98-37A-SH1), is not preserved in the geologic polygon table.***

    UNIT
    Generic geologic map unit labels (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    HFELSHornfels near intrusions are very dark gray to black, very fine to fine grained, hard, dense rocks with common disoriented crystals or rosettes of muscovite, biotite, and locally andalusite. Typically formed by contact metamorphism.

    hflsa2_comp_polygon.shp
    Object type is vector, there are 595 rows associated with this entity, and the entity values refer to comprehensive geologic polygons (Source: Alaska Division of Geological & Geophysical Surveys)

    SUNIT
    Surficial geologic map unit labels (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    bExposed bedrock - bedrock with essentially no cover
    bcThinly covered bedrock - bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris
    QafAlluvial fan deposits - Fan-shaped, heterogeneous mixtures of gravel with some sand and silt and few to numerous, subangular to rounded boulders, especially in proximal areas; clasts locally derived; may include debris-flow deposits; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels; locally covered by reworked silt.
    QaAlluvium in modern stream channels - Elongated deposits of stratified gravel and sand with few to numerous boulders underlying active streams, flood plains, and associated low terraces; well sorted and medium to thick bedded, locally cross-bedded; shows fining-upward cycles.
    QapAlluvial plain deposits - Irregular blankets and low-angle fans of stratified gravel and sand with silt interbeds and few to numerous boulders underlying much of Baker Creek flats; well sorted and medium to thick bedded, locally cross-bedded; surface flat to gently sloping with numerous shallow, interconnected channels
    QasSilty alluvium in modern stream channels - Irregular, elongated deposits of stratified silt beneath modern channels and flood plains of streams draining loess-mantled slopes; may include fine-grained debris flow deposits, especially in the upper reaches; moderately to well sorted and medium to thin bedded, locally cross-bedded.
    QfpFloodplain alluvium bordering modern streams - Elongated deposits of stratified pebble-cobble gravel and medium sand with few to numerous boulders forming modern flood plains and associated low (~3 m) terraces; typically mantled by thin layer of silty over-bank deposits
    QsfSilt fan deposits - Fan-shaped deposits of dark brown to gray silt with some sand and angular to subrounded pebbles in proximal areas; may include fine-grained debris flow deposits, especially in the upper reaches; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels
    QacUndifferentiated alluvial and colluvial valley-fill deposits - Fan-shaped and elongated heterogeneous mixtures of subangular rock fragments and gravel with some silt and sand deposited in upper stream courses primarily by brief, intense summer stream flow, debris flows, and gelifluction; surface smooth, except for local low scarps and shallow, steep-sided channels.
    QcUndifferentiated colluvium - Irregular, heterogeneous blankets, aprons, and fans of angular to subrounded rock fragments, gravel, sand, and silt that are left on slopes, slope bases, or high-level surfaces by residual weathering and complex mass-movement processes, including rolling, sliding, flowing, gelifluction, and frost creep
    QcaColluvial apron and fan deposits - Apron- and fan-shaped, heterogeneous mixtures of angular rock fragments with trace to some gravel, sand, and silt deposited at the bases of steep walls of modern stream valleys; may include or be capped by a considerable amount of redeposited eolian silt; locally washed by meltwater and slope runoff; surface steep to gently sloping.
    QelLoess - Homogeneous blankets of well-sorted, mottled, light grayish-brown silt deposited by eolian processes; generally structureless, but with broadly horizontal bedding and some laminations, wavy bedding, and small-scale cross-bedding; contains scattered small charcoal fragments and root casts; local cryoturbation structures
    QelpPitted loess - Homogeneous blankets of mottled, light grayish-brown silt and organic silt deposited by eolian processes and subsequently modified by melting of ice-rich permafrost; generally massive to locally bedded
    QerReworked upland silt - Heterogeneous blankets of silt and organic silt originally laid down by eolian processes and subsequent minor to extensive reworking by fluvial and colluvial processes; includes silt-rich debris-flow deposits; may contain angular clasts of local origin; massive to thinly bedded, with some wavy bedding and cross-bedding; commonly perennially frozen and ice rich
    QsSwamp deposits - Semicircular to irregular deposits of silt and peat in poorly-drained areas; saturated and locally frozen below a depth of about 1 m, locally ice rich; surface flat and smooth, may have standing water.
    QmtMine tailings - Water-washed pebble-cobble gravel with trace to some sand reworked by placer mining operations; typically well sorted; surface irregular or forming symmetrical ridges and cones.

    UNIT
    Generic geologic map unit labels (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    HFELSHornfels near intrusions are very dark gray to black, very fine to fine grained, hard, dense rocks with common disoriented crystals or rosettes of muscovite, biotite, and locally andalusite. Typically formed by contact metamorphism.
    NMNot mapped, region is irrelevant and not meaningful for the particular data layer

    tana1bedcon_arc.shp
    Object type is vector, there are 844 rows associated with this entity, and the entity values refer to comprehensive geologic unit contacts (Source: Alaska Division of Geological & Geophysical Surveys)

    CODE
    Line symbols for contacts, defined as boundaries between geologic formations or other rock units (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    0Hidden line, defines the polygon boundary, but is not displayed on the map for aesthetic purposes
    5Contact
    9Contact, concealed, generally buried beneath a mapped geologic unit, water, or ice

    SUNIT
    Surficial geologic map unit labels (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    bExposed bedrock - bedrock with essentially no cover
    bcThinly covered bedrock - bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris
    QafAlluvial fan deposits - Fan-shaped, heterogeneous mixtures of gravel with some sand and silt and few to numerous, subangular to rounded boulders, especially in proximal areas; clasts locally derived; may include debris-flow deposits; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels; locally covered by reworked silt.
    QaAlluvium in modern stream channels - Elongated deposits of stratified gravel and sand with few to numerous boulders underlying active streams, flood plains, and associated low terraces; well sorted and medium to thick bedded, locally cross-bedded; shows fining-upward cycles.
    QapAlluvial plain deposits - Irregular blankets and low-angle fans of stratified gravel and sand with silt interbeds and few to numerous boulders underlying much of Baker Creek flats; well sorted and medium to thick bedded, locally cross-bedded; surface flat to gently sloping with numerous shallow, interconnected channels
    QasSilty alluvium in modern stream channels - Irregular, elongated deposits of stratified silt beneath modern channels and flood plains of streams draining loess-mantled slopes; may include fine-grained debris flow deposits, especially in the upper reaches; moderately to well sorted and medium to thin bedded, locally cross-bedded.
    QfpFloodplain alluvium bordering modern streams - Elongated deposits of stratified pebble-cobble gravel and medium sand with few to numerous boulders forming modern flood plains and associated low (~3 m) terraces; typically mantled by thin layer of silty over-bank deposits
    QsfSilt fan deposits - Fan-shaped deposits of dark brown to gray silt with some sand and angular to subrounded pebbles in proximal areas; may include fine-grained debris flow deposits, especially in the upper reaches; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels
    QagOld, high-level alluvial gravels - Irregular residual deposits of gold-bearing, pebble-cobble gravel with well rounded quartzite boulders up to 3 m diameter preserved on high interfluves in the Eureka Creek area; up to 4 m thick, but generally much thinner; locally extensively reworked by mining activity
    QacUndifferentiated alluvial and colluvial valley-fill deposits - Fan-shaped and elongated heterogeneous mixtures of subangular rock fragments and gravel with some silt and sand deposited in upper stream courses primarily by brief, intense summer stream flow, debris flows, and gelifluction; surface smooth, except for local low scarps and shallow, steep-sided channels.
    QcUndifferentiated colluvium - Irregular, heterogeneous blankets, aprons, and fans of angular to subrounded rock fragments, gravel, sand, and silt that are left on slopes, slope bases, or high-level surfaces by residual weathering and complex mass-movement processes, including rolling, sliding, flowing, gelifluction, and frost creep
    QcaColluvial apron and fan deposits - Apron- and fan-shaped, heterogeneous mixtures of angular rock fragments with trace to some gravel, sand, and silt deposited at the bases of steep walls of modern stream valleys; may include or be capped by a considerable amount of redeposited eolian silt; locally washed by meltwater and slope runoff; surface steep to gently sloping.
    QelLoess - Homogeneous blankets of well-sorted, mottled, light grayish-brown silt deposited by eolian processes; generally structureless, but with broadly horizontal bedding and some laminations, wavy bedding, and small-scale cross-bedding; contains scattered small charcoal fragments and root casts; local cryoturbation structures
    QelpPitted loess - Homogeneous blankets of mottled, light grayish-brown silt and organic silt deposited by eolian processes and subsequently modified by melting of ice-rich permafrost; generally massive to locally bedded
    QerReworked upland silt - Heterogeneous blankets of silt and organic silt originally laid down by eolian processes and subsequent minor to extensive reworking by fluvial and colluvial processes; includes silt-rich debris-flow deposits; may contain angular clasts of local origin; massive to thinly bedded, with some wavy bedding and cross-bedding; commonly perennially frozen and ice rich
    QsSwamp deposits - Semicircular to irregular deposits of silt and peat in poorly-drained areas; saturated and locally frozen below a depth of about 1 m, locally ice rich; surface flat and smooth, may have standing water.
    QmtMine tailings - Water-washed pebble-cobble gravel with trace to some sand reworked by placer mining operations; typically well sorted; surface irregular or forming symmetrical ridges and cones.

    tana2bedcon_arc.shp
    Object type is vector, there are 1,244 rows associated with this entity, and the entity values refer to comprehensive geologic unit contacts (Source: Alaska Division of Geological & Geophysical Surveys)

    CODE
    Line symbols for contacts, defined as boundaries between geologic formations or other rock units (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    0Hidden line, defines the polygon boundary, but is not displayed on the map for aesthetic purposes
    5Contact
    9Contact, concealed, generally buried beneath a mapped geologic unit, water, or ice

    SUNIT
    Surficial geologic map unit labels (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    bExposed bedrock- bedrock with essentially no cover
    bcThinly covered bedrock- bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris
    QafAlluvial fan deposits - Fan-shaped, heterogeneous mixtures of gravel with some sand and silt and few to numerous, subangular to rounded boulders, especially in proximal areas; clasts locally derived; may include debris-flow deposits; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels; locally covered by reworked silt.
    QaAlluvium in modern stream channels - Elongated deposits of stratified gravel and sand with few to numerous boulders underlying active streams, flood plains, and associated low terraces; well sorted and medium to thick bedded, locally cross-bedded; shows fining-upward cycles.
    QapAlluvial plain deposits - Irregular blankets and low-angle fans of stratified gravel and sand with silt interbeds and few to numerous boulders underlying much of Baker Creek flats; well sorted and medium to thick bedded, locally cross-bedded; surface flat to gently sloping with numerous shallow, interconnected channels
    QasSilty alluvium in modern stream channels - Irregular, elongated deposits of stratified silt beneath modern channels and flood plains of streams draining loess-mantled slopes; may include fine-grained debris flow deposits, especially in the upper reaches; moderately to well sorted and medium to thin bedded, locally cross-bedded.
    QfpFloodplain alluvium bordering modern streams - Elongated deposits of stratified pebble-cobble gravel and medium sand with few to numerous boulders forming modern flood plains and associated low (~3 m) terraces; typically mantled by thin layer of silty over-bank deposits
    QsfSilt fan deposits - Fan-shaped deposits of dark brown to gray silt with some sand and angular to subrounded pebbles in proximal areas; may include fine-grained debris flow deposits, especially in the upper reaches; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels
    QacUndifferentiated alluvial and colluvial valley-fill deposits - Fan-shaped and elongated heterogeneous mixtures of subangular rock fragments and gravel with some silt and sand deposited in upper stream courses primarily by brief, intense summer stream flow, debris flows, and gelifluction; surface smooth, except for local low scarps and shallow, steep-sided channels.
    QcUndifferentiated colluvium - Irregular, heterogeneous blankets, aprons, and fans of angular to subrounded rock fragments, gravel, sand, and silt that are left on slopes, slope bases, or high-level surfaces by residual weathering and complex mass-movement processes, including rolling, sliding, flowing, gelifluction, and frost creep
    QcaColluvial apron and fan deposits - Apron- and fan-shaped, heterogeneous mixtures of angular rock fragments with trace to some gravel, sand, and silt deposited at the bases of steep walls of modern stream valleys; may include or be capped by a considerable amount of redeposited eolian silt; locally washed by meltwater and slope runoff; surface steep to gently sloping.
    QelLoess - Homogeneous blankets of well-sorted, mottled, light grayish-brown silt deposited by eolian processes; generally structureless, but with broadly horizontal bedding and some laminations, wavy bedding, and small-scale cross-bedding; contains scattered small charcoal fragments and root casts; local cryoturbation structures
    QelpPitted loess - Homogeneous blankets of mottled, light grayish-brown silt and organic silt deposited by eolian processes and subsequently modified by melting of ice-rich permafrost; generally massive to locally bedded
    QerReworked upland silt - Heterogeneous blankets of silt and organic silt originally laid down by eolian processes and subsequent minor to extensive reworking by fluvial and colluvial processes; includes silt-rich debris-flow deposits; may contain angular clasts of local origin; massive to thinly bedded, with some wavy bedding and cross-bedding; commonly perennially frozen and ice rich
    QsSwamp deposits - Semicircular to irregular deposits of silt and peat in poorly drained areas; saturated and locally frozen below a depth of about 1 m, locally ice rich; surface flat and smooth, may have standing water.
    QmtMine tailings - Water-washed pebble-cobble gravel with trace to some sand reworked by placer mining operations; typically well sorted; surface irregular or forming symmetrical ridges and cones.

    tana1strline_arc.shp
    Object type is vector, there are 976 rows associated with this entity, and the entity values refer to types of faults (Source: Alaska Division of Geological & Geophysical Surveys)

    CODE
    Line symbols for types of faults (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    11Fault
    12Fault approximately located
    15Fault, concealed, generally under overlying mapped deposits, ice, or water. ***Note: arcs having the software-defined attribute/column FID whose values are 630, 633, 635, 636, 643, 644, 670, 672, 682, 686, 689, 690, 696, 698, 701, 702, 704-706, and 708 represent the Stevens Creek Fault (continued in the Entity_Attribute_Layer "tana2strline" listed below). The annotation "Stevens Creek Fault", as seen on the Preliminary Geologic Map of the Tanana A-1 and A-2 Quadrangles, Central Alaska (Publication PDF98-37A-SH1), is not preserved in the structure table.***
    17Thrust fault, sawteeth on upper plate, user will need to see the Preliminary Geologic Map of the Tanana A-1 and A-2 Quadrangles, Central Alaska (Publication PDF98-37A-SH1) for interpretation of relative plate motion
    18Thrust fault, approximately located, user will need to see the Preliminary Geologic Map of the Tanana A-1 and A-2 Quadrangles, Central Alaska (Publication PDF98-37A-SH1) for interpretation of relative plate motion
    20Thrust fault, probable, user will need to see the Preliminary Geologic Map of the Tanana A-1 and A-2 Quadrangles, Central Alaska (Publication PDF98-37A-SH1) for interpretation of relative plate motion
    22Thrust fault, concealed, user will need to see the Preliminary Geologic Map of the Tanana A-1 and A-2 Quadrangles, Central Alaska (Publication PDF98-37A-SH1) for interpretation of relative plate motion

    SUNIT
    Surficial geologic map unit labels (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    bExposed bedrock- bedrock with essentially no cover
    bcThinly covered bedrock - bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris
    QafAlluvial fan deposits - Fan-shaped, heterogeneous mixtures of gravel with some sand and silt and few to numerous, subangular to rounded boulders, especially in proximal areas; clasts locally derived; may include debris-flow deposits; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels; locally covered by reworked silt.
    QaAlluvium in modern stream channels - Elongated deposits of stratified gravel and sand with few to numerous boulders underlying active streams, flood plains, and associated low terraces; well sorted and medium to thick bedded, locally cross-bedded; shows fining-upward cycles.
    QapAlluvial plain deposits - Irregular blankets and low-angle fans of stratified gravel and sand with silt interbeds and few to numerous boulders underlying much of Baker Creek flats; well sorted and medium to thick bedded, locally cross-bedded; surface flat to gently sloping with numerous shallow, interconnected channels
    QasSilty alluvium in modern stream channels - Irregular, elongated deposits of stratified silt beneath modern channels and flood plains of streams draining loess-mantled slopes; may include fine-grained debris flow deposits, especially in the upper reaches; moderately to well sorted and medium to thin bedded, locally cross-bedded.
    QfpFloodplain alluvium bordering modern streams-Elongated deposits of stratified pebble-cobble gravel and medium sand with few to numerous boulders forming modern flood plains and associated low (~3 m) terraces; typically mantled by thin layer of silty over-bank deposits
    QsfSilt fan deposits - Fan-shaped deposits of dark brown to gray silt with some sand and angular to subrounded pebbles in proximal areas; may include fine-grained debris flow deposits, especially in the upper reaches; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels
    QagOld, high-level alluvial gravels - Irregular residual deposits of gold-bearing, pebble-cobble gravel with well rounded quartzite boulders up to 3 m diameter preserved on high interfluves in the Eureka Creek area; up to 4 m thick, but generally much thinner; locally extensively reworked by mining activity
    QacUndifferentiated alluvial and colluvial valley-fill deposits - Fan-shaped and elongated heterogeneous mixtures of subangular rock fragments and gravel with some silt and sand deposited in upper stream courses primarily by brief, intense summer stream flow, debris flows, and gelifluction; surface smooth, except for local low scarps and shallow, steep-sided channels.
    QcUndifferentiated colluvium - Irregular, heterogeneous blankets, aprons, and fans of angular to subrounded rock fragments, gravel, sand, and silt that are left on slopes, slope bases, or high-level surfaces by residual weathering and complex mass-movement processes, including rolling, sliding, flowing, gelifluction, and frost creep
    QcaColluvial apron and fan deposits - Apron- and fan-shaped, heterogeneous mixtures of angular rock fragments with trace to some gravel, sand, and silt deposited at the bases of steep walls of modern stream valleys; may include or be capped by a considerable amount of redeposited eolian silt; locally washed by meltwater and slope runoff; surface steep to gently sloping.
    QelLoess - Homogeneous blankets of well-sorted, mottled, light grayish-brown silt deposited by eolian processes; generally structureless, but with broadly horizontal bedding and some laminations, wavy bedding, and small-scale cross-bedding; contains scattered small charcoal fragments and root casts; local cryoturbation structures
    QelpPitted loess - Homogeneous blankets of mottled, light grayish-brown silt and organic silt deposited by eolian processes and subsequently modified by melting of ice-rich permafrost; generally massive to locally bedded
    QerReworked upland silt - Heterogeneous blankets of silt and organic silt originally laid down by eolian processes and subsequent minor to extensive reworking by fluvial and colluvial processes; includes silt-rich debris-flow deposits; may contain angular clasts of local origin; massive to thinly bedded, with some wavy bedding and cross-bedding; commonly perennially frozen and ice rich
    QsSwamp deposits - Semicircular to irregular deposits of silt and peat in poorly-drained areas; saturated and locally frozen below a depth of about 1 m, locally ice rich; surface flat and smooth, may have standing water.
    QmtMine tailings - Water-washed pebble-cobble gravel with trace to some sand reworked by placer mining operations; typically well sorted; surface irregular or forming symmetrical ridges and cones.

    tana2strline_arc.shp
    Object type is vector, there are 1,103 rows associated with this entity, and the entity values refer to types of faults (Source: Alaska Division of Geological & Geophysical Surveys)

    CODE
    Line symbols for types of faults (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    11Fault
    12Fault approximately located
    15Fault, concealed, generally under overlying mapped deposits, ice, or water. ***Note: arcs having the software-defined attribute/column FID whose values are 39, 41, 58, 59, 73, 85, 92, 96, 118, 121, 123, 143, 145, 149, 159, 166, 168, 178, 179, 183, 208, 209, 211, 217, 218, 224, 232, 235, 239, 249, 253, 254, 216, 267, 291, 303, 306, 315, 351, 364, 439, 452, 488, 493, 506, 515, 529, 531, 546, 548, 550, 553, 556, 568, and 580 represent the Stevens Creek Fault (continued from the Entity_Attribute_Layer "tana1strline" listed above). Arcs having the software-defined attribute/column FID whose values are 1-7, 11, 13, 15, 19, 20, 24, 27, 28, 36, 54, 56, 60, 65, 67, 69, 72, 74, and 79 represent the Kaltag Fault Zone. The annotations "Stevens Creek Fault" and "Kaltag Fault Zone", as seen on the Preliminary Geologic Map of the Tanana A-1 and A-2 Quadrangles, Central Alaska (Publication PDF98-37A-SH1), are not preserved in the structure table.***
    17Thrust fault, sawteeth on upper plate, user will need to see the Preliminary Geologic Map of the Tanana A-1 and A-2 Quadrangles, Central Alaska (Publication PDF98-37A-SH1) for interpretation of relative plate motion
    18Thrust fault, approximately located, user will need to see the Preliminary Geologic Map of the Tanana A-1 and A-2 Quadrangles, Central Alaska (Publication PDF98-37A-SH1) for interpretation of relative plate motion
    22Thrust fault, concealed, user will need to see the Preliminary Geologic Map of the Tanana A-1 and A-2 Quadrangles, Central Alaska (Publication PDF98-37A-SH1) for interpretation of relative plate motion

    SUNIT
    Surficial geologic map unit labels (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    bExposed bedrock - bedrock with essentially no cover
    bcThinly covered bedrock - bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris
    QafAlluvial fan deposits - Fan-shaped, heterogeneous mixtures of gravel with some sand and silt and few to numerous, subangular to rounded boulders, especially in proximal areas; clasts locally derived; may include debris-flow deposits; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels; locally covered by reworked silt.
    QaAlluvium in modern stream channels - Elongated deposits of stratified gravel and sand with few to numerous boulders underlying active streams, flood plains, and associated low terraces; well sorted and medium to thick bedded, locally cross-bedded; shows fining-upward cycles.
    QapAlluvial plain deposits - Irregular blankets and low-angle fans of stratified gravel and sand with silt interbeds and few to numerous boulders underlying much of Baker Creek flats; well sorted and medium to thick bedded, locally cross-bedded; surface flat to gently sloping with numerous shallow, interconnected channels
    QasSilty alluvium in modern stream channels - Irregular, elongated deposits of stratified silt beneath modern channels and flood plains of streams draining loess-mantled slopes; may include fine-grained debris flow deposits, especially in the upper reaches; moderately to well sorted and medium to thin bedded, locally cross-bedded.
    QfpFloodplain alluvium bordering modern streams - Elongated deposits of stratified pebble-cobble gravel and medium sand with few to numerous boulders forming modern flood plains and associated low (~3 m) terraces; typically mantled by thin layer of silty over-bank deposits
    QsfSilt fan deposits - Fan-shaped deposits of dark brown to gray silt with some sand and angular to subrounded pebbles in proximal areas; may include fine-grained debris flow deposits, especially in the upper reaches; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels
    QacUndifferentiated alluvial and colluvial valley-fill deposits - Fan-shaped and elongated heterogeneous mixtures of subangular rock fragments and gravel with some silt and sand deposited in upper stream courses primarily by brief, intense summer stream flow, debris flows, and gelifluction; surface smooth, except for local low scarps and shallow, steep-sided channels.
    QcUndifferentiated colluvium - Irregular, heterogeneous blankets, aprons, and fans of angular to subrounded rock fragments, gravel, sand, and silt that are left on slopes, slope bases, or high-level surfaces by residual weathering and complex mass-movement processes, including rolling, sliding, flowing, gelifluction, and frost creep
    QcaColluvial apron and fan deposits - Apron- and fan-shaped, heterogeneous mixtures of angular rock fragments with trace to some gravel, sand, and silt deposited at the bases of steep walls of modern stream valleys; may include or be capped by a considerable amount of redeposited eolian silt; locally washed by meltwater and slope runoff; surface steep to gently sloping.
    QelLoess - Homogeneous blankets of well-sorted, mottled, light grayish-brown silt deposited by eolian processes; generally structureless, but with broadly horizontal bedding and some laminations, wavy bedding, and small-scale cross-bedding; contains scattered small charcoal fragments and root casts; local cryoturbation structures
    QelpPitted loess - Homogeneous blankets of mottled, light grayish-brown silt and organic silt deposited by eolian processes and subsequently modified by melting of ice-rich permafrost; generally massive to locally bedded
    QerReworked upland silt - Heterogeneous blankets of silt and organic silt originally laid down by eolian processes and subsequent minor to extensive reworking by fluvial and colluvial processes; includes silt-rich debris-flow deposits; may contain angular clasts of local origin; massive to thinly bedded, with some wavy bedding and cross-bedding; commonly perennially frozen and ice rich
    QsSwamp deposits - Semicircular to irregular deposits of silt and peat in poorly-drained areas; saturated and locally frozen below a depth of about 1 m, locally ice rich; surface flat and smooth, may have standing water.
    QmtMine tailings - Water-washed pebble-cobble gravel with trace to some sand reworked by placer mining operations; typically well sorted; surface irregular or forming symmetrical ridges and cones.

    tana1srf_polygon.shp
    Object type is vector, there are 490 rows associated with this entity, and the entity values refer to comprehensive geologic polygons (Source: Alaska Division of Geological & Geophysical Surveys)

    SUNIT
    Surficial geologic map unit labels (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    bExposed bedrock - bedrock with essentially no cover
    bcThinly covered bedrock - bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris
    QafAlluvial fan deposits - Fan-shaped, heterogeneous mixtures of gravel with some sand and silt and few to numerous, subangular to rounded boulders, especially in proximal areas; clasts locally derived; may include debris-flow deposits; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels; locally covered by reworked silt.
    QaAlluvium in modern stream channels - Elongated deposits of stratified gravel and sand with few to numerous boulders underlying active streams, flood plains, and associated low terraces; well sorted and medium to thick bedded, locally cross-bedded; shows fining-upward cycles.
    QapAlluvial plain deposits - Irregular blankets and low-angle fans of stratified gravel and sand with silt interbeds and few to numerous boulders underlying much of Baker Creek flats; well sorted and medium to thick bedded, locally cross-bedded; surface flat to gently sloping with numerous shallow, interconnected channels
    QasSilty alluvium in modern stream channels - Irregular, elongated deposits of stratified silt beneath modern channels and flood plains of streams draining loess-mantled slopes; may include fine-grained debris flow deposits, especially in the upper reaches; moderately to well sorted and medium to thin bedded, locally cross-bedded.
    QfpFloodplain alluvium bordering modern streams - Elongated deposits of stratified pebble-cobble gravel and medium sand with few to numerous boulders forming modern flood plains and associated low (~3 m) terraces; typically mantled by thin layer of silty over-bank deposits
    QsfSilt fan deposits - Fan-shaped deposits of dark brown to gray silt with some sand and angular to subrounded pebbles in proximal areas; may include fine-grained debris flow deposits, especially in the upper reaches; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels
    QagOld, high-level alluvial gravels - Irregular residual deposits of gold-bearing, pebble-cobble gravel with well rounded quartzite boulders up to 3 m diameter preserved on high interfluves in the Eureka Creek area; up to 4 m thick, but generally much thinner; locally extensively reworked by mining activity
    QacUndifferentiated alluvial and colluvial valley-fill deposits - Fan-shaped and elongated heterogeneous mixtures of subangular rock fragments and gravel with some silt and sand deposited in upper stream courses primarily by brief, intense summer stream flow, debris flows, and gelifluction; surface smooth, except for local low scarps and shallow, steep-sided channels.
    QcUndifferentiated colluvium - Irregular, heterogeneous blankets, aprons, and fans of angular to subrounded rock fragments, gravel, sand, and silt that are left on slopes, slope bases, or high-level surfaces by residual weathering and complex mass-movement processes, including rolling, sliding, flowing, gelifluction, and frost creep
    QcaColluvial apron and fan deposits - Apron- and fan-shaped, heterogeneous mixtures of angular rock fragments with trace to some gravel, sand, and silt deposited at the bases of steep walls of modern stream valleys; may include or be capped by a considerable amount of redeposited eolian silt; locally washed by meltwater and slope runoff; surface steep to gently sloping.
    QelLoess - Homogeneous blankets of well-sorted, mottled, light grayish-brown silt deposited by eolian processes; generally structureless, but with broadly horizontal bedding and some laminations, wavy bedding, and small-scale cross-bedding; contains scattered small charcoal fragments and root casts; local cryoturbation structures
    QelpPitted loess - Homogeneous blankets of mottled, light grayish-brown silt and organic silt deposited by eolian processes and subsequently modified by melting of ice-rich permafrost; generally massive to locally bedded
    QerReworked upland silt - Heterogeneous blankets of silt and organic silt originally laid down by eolian processes and subsequent minor to extensive reworking by fluvial and colluvial processes; includes silt-rich debris-flow deposits; may contain angular clasts of local origin; massive to thinly bedded, with some wavy bedding and cross-bedding; commonly perennially frozen and ice rich
    QldDelta deposits - Fan-shaped, heterogeneous mixture of well sorted silt, sand, and gravel; thick to thin bedded; shows cross-bedding and fining-upward cycles; surface smooth, except for numerous shallow, interconnected channels.
    QsSwamp deposits - Semicircular to irregular deposits of silt and peat in poorly-drained areas; saturated and locally frozen below a depth of about 1 m, locally ice rich; surface flat and smooth, may have standing water.
    QmtMine tailings - Water-washed pebble-cobble gravel with trace to some sand reworked by placer mining operations; typically well sorted; surface irregular or forming symmetrical ridges and cones.
    WATERBody of water. ***Note: the polygon having the software-defined attribute/column FID whose value is 441 represents Baker Lake. The annotation "Baker Lake", as seen on the Preliminary Geologic Map of the Tanana A-1 and A-2 Quadrangles, Central Alaska (Publication PDF98-37A-SH1), is not preserved in the geologic polygon table.***

    tana2srf_polygon.shp
    Object type is vector, there are 438 rows associated with this entity, and the entity values refer to comprehensive geologic polygons (Source: Alaska Division of Geological & Geophysical Surveys)

    SUNIT
    Surficial geologic map unit labels (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    bExposed bedrock - bedrock with essentially no cover
    bcThinly covered bedrock - bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris
    QafAlluvial fan deposits - Fan-shaped, heterogeneous mixtures of gravel with some sand and silt and few to numerous, subangular to rounded boulders, especially in proximal areas; clasts locally derived; may include debris-flow deposits; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels; locally covered by reworked silt.
    QaAlluvium in modern stream channels - Elongated deposits of stratified gravel and sand with few to numerous boulders underlying active streams, flood plains, and associated low terraces; well sorted and medium to thick bedded, locally cross-bedded; shows fining-upward cycles.
    QapAlluvial plain deposits - Irregular blankets and low-angle fans of stratified gravel and sand with silt interbeds and few to numerous boulders underlying much of Baker Creek flats; well sorted and medium to thick bedded, locally cross-bedded; surface flat to gently sloping with numerous shallow, interconnected channels
    QasSilty alluvium in modern stream channels - Irregular, elongated deposits of stratified silt beneath modern channels and flood plains of streams draining loess-mantled slopes; may include fine-grained debris flow deposits, especially in the upper reaches; moderately to well sorted and medium to thin bedded, locally cross-bedded.
    QfpFloodplain alluvium bordering modern streams - Elongated deposits of stratified pebble-cobble gravel and medium sand with few to numerous boulders forming modern flood plains and associated low (~3 m) terraces; typically mantled by thin layer of silty over-bank deposits
    QsfSilt fan deposits - Fan-shaped deposits of dark brown to gray silt with some sand and angular to subrounded pebbles in proximal areas; may include fine-grained debris flow deposits, especially in the upper reaches; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels
    QacUndifferentiated alluvial and colluvial valley-fill deposits - Fan-shaped and elongated heterogeneous mixtures of subangular rock fragments and gravel with some silt and sand deposited in upper stream courses primarily by brief, intense summer stream flow, debris flows, and gelifluction; surface smooth, except for local low scarps and shallow, steep-sided channels.
    QcUndifferentiated colluvium - Irregular, heterogeneous blankets, aprons, and fans of angular to subrounded rock fragments, gravel, sand, and silt that are left on slopes, slope bases, or high-level surfaces by residual weathering and complex mass-movement processes, including rolling, sliding, flowing, gelifluction, and frost creep
    QcaColluvial apron and fan deposits - Apron- and fan-shaped, heterogeneous mixtures of angular rock fragments with trace to some gravel, sand, and silt deposited at the bases of steep walls of modern stream valleys; may include or be capped by a considerable amount of redeposited eolian silt; locally washed by meltwater and slope runoff; surface steep to gently sloping.
    QelLoess - Homogeneous blankets of well-sorted, mottled, light grayish-brown silt deposited by eolian processes; generally structureless, but with broadly horizontal bedding and some laminations, wavy bedding, and small-scale cross-bedding; contains scattered small charcoal fragments and root casts; local cryoturbation structures
    QelpPitted loess - Homogeneous blankets of mottled, light grayish-brown silt and organic silt deposited by eolian processes and subsequently modified by melting of ice-rich permafrost; generally massive to locally bedded
    QerReworked upland silt - Heterogeneous blankets of silt and organic silt originally laid down by eolian processes and subsequent minor to extensive reworking by fluvial and colluvial processes; includes silt-rich debris-flow deposits; may contain angular clasts of local origin; massive to thinly bedded, with some wavy bedding and cross-bedding; commonly perennially frozen and ice rich
    QsSwamp deposits - Semicircular to irregular deposits of silt and peat in poorly-drained areas; saturated and locally frozen below a depth of about 1 m, locally ice rich; surface flat and smooth, may have standing water.
    QmtMine tailings - Water-washed pebble-cobble gravel with trace to some sand reworked by placer mining operations; typically well sorted; surface irregular or forming symmetrical ridges and cones.

    tana1fld_point.shp
    Object type is point, there are 9 rows associated with this entity, and the entity values refer to types of anticlines or synclines (Source: Alaska Division of Geological & Geophysical Surveys)

    CODE
    Point symbols for types of folds, anticlines, or synclines (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    22Anticline
    23Syncline
    27Overturned anticline, showing direction of dip of limbs

    tana2fld_point.shp
    Object type is point, there are 31 rows associated with this entity, and the entity values refer to types of anticlines or synclines (Source: Alaska Division of Geological & Geophysical Surveys)

    CODE
    Point symbols for types of folds, anticlines, or synclines (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    22Anticline
    23Syncline
    26Overturned syncline, showing direction of dip of limbs

    tana1fldline_arc.shp
    Object type is vector, there are 211 rows associated with this entity, and the entity values refer to types of folds, anticlines, synclines, or lines depicting a cross-section (Source: Alaska Division of Geological & Geophysical Surveys)

    CODE
    Line symbols for types of folds, anticlines, synclines, or lines depicting a cross-section (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    4Generic line depicting a type of fold, anticline, syncline, or cross-section location
    34Fold axis. This line, in combination with the proper point symbol, indicates the location of an anticline or syncline (see Entity_Type_Label "tana1fld.pat" above).
    36Inferred anticline or syncline. This line, in combination with the proper point symbol, indicates the location of an anticline or syncline (see Entity_Type_Label "tana1fld.pat" above).
    38Anticline or syncline, concealed. This line, in combination with the proper point symbol, indicates the location of an anticline or syncline (see Entity_Type_Label "tana1fld.pat" above).

    XSECT
    Indicates whether or not the line represents a cross-section. (Source: Alaska Division of Geological & Geophysical Surveys)

    "Yes" - The line represents a cross-section. "No" - The line does not represent a cross-section.

    SUNIT
    Surficial geologic map unit labels (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    bExposed bedrock - bedrock with essentially no cover
    bcThinly covered bedrock - bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris
    QaAlluvium in modern stream channels - Elongated deposits of stratified gravel and sand with few to numerous boulders underlying active streams, flood plains, and associated low terraces; well sorted and medium to thick bedded, locally cross-bedded; shows fining-upward cycles.
    QapAlluvial plain deposits - Irregular blankets and low-angle fans of stratified gravel and sand with silt interbeds and few to numerous boulders underlying much of Baker Creek flats; well sorted and medium to thick bedded, locally cross-bedded; surface flat to gently sloping with numerous shallow, interconnected channels
    QasSilty alluvium in modern stream channels - Irregular, elongated deposits of stratified silt beneath modern channels and flood plains of streams draining loess-mantled slopes; may include fine-grained debris flow deposits, especially in the upper reaches; moderately to well sorted and medium to thin bedded, locally cross-bedded.
    QfpFloodplain alluvium bordering modern streams - Elongated deposits of stratified pebble-cobble gravel and medium sand with few to numerous boulders forming modern flood plains and associated low (~3 m) terraces; typically mantled by thin layer of silty over-bank deposits
    QsfSilt fan deposits - Fan-shaped deposits of dark brown to gray silt with some sand and angular to subrounded pebbles in proximal areas; may include fine-grained debris flow deposits, especially in the upper reaches; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels
    QagOld, high-level alluvial gravels - Irregular residual deposits of gold-bearing, pebble-cobble gravel with well rounded quartzite boulders up to 3 m diameter preserved on high interfluves in the Eureka Creek area; up to 4 m thick, but generally much thinner; locally extensively reworked by mining activity
    QacUndifferentiated alluvial and colluvial valley-fill deposits - Fan-shaped and elongated heterogeneous mixtures of subangular rock fragments and gravel with some silt and sand deposited in upper stream courses primarily by brief, intense summer stream flow, debris flows, and gelifluction; surface smooth, except for local low scarps and shallow, steep-sided channels.
    QcUndifferentiated colluvium - Irregular, heterogeneous blankets, aprons, and fans of angular to subrounded rock fragments, gravel, sand, and silt that are left on slopes, slope bases, or high-level surfaces by residual weathering and complex mass-movement processes, including rolling, sliding, flowing, gelifluction, and frost creep
    QcaColluvial apron and fan deposits - Apron- and fan-shaped, heterogeneous mixtures of angular rock fragments with trace to some gravel, sand, and silt deposited at the bases of steep walls of modern stream valleys; may include or be capped by a considerable amount of redeposited eolian silt; locally washed by meltwater and slope runoff; surface steep to gently sloping.
    QelLoess - Homogeneous blankets of well-sorted, mottled, light grayish-brown silt deposited by eolian processes; generally structureless, but with broadly horizontal bedding and some laminations, wavy bedding, and small-scale cross-bedding; contains scattered small charcoal fragments and root casts; local cryoturbation structures
    QelpPitted loess - Homogeneous blankets of mottled, light grayish-brown silt and organic silt deposited by eolian processes and subsequently modified by melting of ice-rich permafrost; generally massive to locally bedded
    QerReworked upland silt--Heterogeneous blankets of silt and organic silt originally laid down by eolian processes and subsequent minor to extensive reworking by fluvial and colluvial processes; includes silt-rich debris-flow deposits; may contain angular clasts of local origin; massive to thinly bedded, with some wavy bedding and cross-bedding; commonly perennially frozen and ice rich
    QsSwamp deposits-Semicircular to irregular deposits of silt and peat in poorly-drained areas; saturated and locally frozen below a depth of about 1 m, locally ice rich; surface flat and smooth, may have standing water.
    QmtMine tailings-Water-washed pebble-cobble gravel with trace to some sand reworked by placer mining operations; typically well sorted; surface irregular or forming symmetrical ridges and cones.

    tana2fldline_arc.shp
    Object type is vector, there are 198 rows associated with this entity, and the entity values refer to types of folds, anticlines, synclines, or lines depicting a cross-section (Source: Alaska Division of Geological & Geophysical Surveys)

    CODE
    Line symbols for types of folds, anticlines, synclines, or lines depicting a cross-section (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    4Generic line depicting a type of fold, anticline, syncline, or cross-section location
    34Fold axis. This line, in combination with the proper point symbol, indicates the location of an anticline or syncline (see Entity_Type_Label "tana2fld.pat" above).
    36Inferred anticline or syncline. This line, in combination with the proper point symbol, indicates the location of an anticline or syncline (see Entity_Type_Label "tana2fld.pat" above).
    38Anticline or syncline, concealed. This line, in combination with the proper point symbol, indicates the location of an anticline or syncline (see Entity_Type_Label "tana2fld.pat" above).

    XSECT
    Indicates whether or not the line represents a cross-section. (Source: Alaska Division of Geological & Geophysical Surveys)

    "Yes" - The line represents a cross-section. "No" - The line does not represent a cross-section.

    SUNIT
    Surficial geologic map unit labels (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    bExposed bedrock - bedrock with essentially no cover
    bcThinly covered bedrock - bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris
    QafAlluvial fan deposits - Fan-shaped, heterogeneous mixtures of gravel with some sand and silt and few to numerous, subangular to rounded boulders, especially in proximal areas; clasts locally derived; may include debris-flow deposits; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels; locally covered by reworked silt.
    QaAlluvium in modern stream channels - Elongated deposits of stratified gravel and sand with few to numerous boulders underlying active streams, flood plains, and associated low terraces; well sorted and medium to thick bedded, locally cross-bedded; shows fining-upward cycles.
    QapAlluvial plain deposits - Irregular blankets and low-angle fans of stratified gravel and sand with silt interbeds and few to numerous boulders underlying much of Baker Creek flats; well sorted and medium to thick bedded, locally cross-bedded; surface flat to gently sloping with numerous shallow, interconnected channels
    QasSilty alluvium in modern stream channels - Irregular, elongated deposits of stratified silt beneath modern channels and flood plains of streams draining loess-mantled slopes; may include fine-grained debris flow deposits, especially in the upper reaches; moderately to well sorted and medium to thin bedded, locally cross-bedded.
    QfpFloodplain alluvium bordering modern streams - Elongated deposits of stratified pebble-cobble gravel and medium sand with few to numerous boulders forming modern flood plains and associated low (~3 m) terraces; typically mantled by thin layer of silty over-bank deposits
    QsfSilt fan deposits - Fan-shaped deposits of dark brown to gray silt with some sand and angular to subrounded pebbles in proximal areas; may include fine-grained debris flow deposits, especially in the upper reaches; thick to thin bedded; surface smooth, except for numerous shallow, interconnected channels
    QacUndifferentiated alluvial and colluvial valley-fill deposits - Fan-shaped and elongated heterogeneous mixtures of subangular rock fragments and gravel with some silt and sand deposited in upper stream courses primarily by brief, intense summer stream flow, debris flows, and gelifluction; surface smooth, except for local low scarps and shallow, steep-sided channels.
    QcUndifferentiated colluvium - Irregular, heterogeneous blankets, aprons, and fans of angular to subrounded rock fragments, gravel, sand, and silt that are left on slopes, slope bases, or high-level surfaces by residual weathering and complex mass-movement processes, including rolling, sliding, flowing, gelifluction, and frost creep
    QcaColluvial apron and fan deposits - Apron- and fan-shaped, heterogeneous mixtures of angular rock fragments with trace to some gravel, sand, and silt deposited at the bases of steep walls of modern stream valleys; may include or be capped by a considerable amount of redeposited eolian silt; locally washed by meltwater and slope runoff; surface steep to gently sloping.
    QelLoess - Homogeneous blankets of well-sorted, mottled, light grayish-brown silt deposited by eolian processes; generally structureless, but with broadly horizontal bedding and some laminations, wavy bedding, and small-scale cross-bedding; contains scattered small charcoal fragments and root casts; local cryoturbation structures
    QelpPitted loess - Homogeneous blankets of mottled, light grayish-brown silt and organic silt deposited by eolian processes and subsequently modified by melting of ice-rich permafrost; generally massive to locally bedded
    QerReworked upland silt - Heterogeneous blankets of silt and organic silt originally laid down by eolian processes and subsequent minor to extensive reworking by fluvial and colluvial processes; includes silt-rich debris-flow deposits; may contain angular clasts of local origin; massive to thinly bedded, with some wavy bedding and cross-bedding; commonly perennially frozen and ice rich
    QsSwamp deposits - Semicircular to irregular deposits of silt and peat in poorly-drained areas; saturated and locally frozen below a depth of about 1 m, locally ice rich; surface flat and smooth, may have standing water.

    tana1bur_arc.shp
    Object type is vector, there are 5 rows associated with this entity, and the entity values refer to various types of geophysical features as described in the accompanying report (Source: Alaska Division of Geological & Geophysical Surveys)

    CODE
    Line symbols for various types of geophysical features (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    0Hidden line, defines the polygon boundary, but is not displayed on the map for aesthetic purposes
    64Buried anomaly, boundary of airborne geophysical signature: high magnetics and low resistivity

    tana2bur_arc.shp
    Object type is vector, there are 5 rows associated with this entity, and the entity values refer to various types of geophysical features as described in the accompanying report (Source: Alaska Division of Geological & Geophysical Surveys)

    CODE
    Line symbols for various types of geophysical features (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    0Hidden line, defines the polygon boundary, but is not displayed on the map for aesthetic purposes
    64Buried anomaly, boundary of airborne geophysical signature: high magnetics and low resistivity
    65Buried anomaly, boundary of airborne geophysical signature: low magnetics and high resistivity

    tana12_att_point.shp
    Object type is point, there are 444 rows associated with this entity, and the entity values refer to the strike, dip, and plunge of bedding planes, foliation, and various lineaments (Source: Alaska Division of Geological & Geophysical Surveys)

    INDEX
    Generic example of unique sample identifier or location of a geologic measurement: YrAAA999X: Yr=2 digit year of sample collection, AAA=geologist's initials (one to three characters), 999=unique station number, X=unique alpha character designating a sample was taken at the field station. Geologists' initials are: BT - B. Taber, DS - D. Stevens, JD - J. Dover, KC - K. Clautice, RB - R. Blodgett, RN - R. Newberry, RR - R. Reifenstuhl, SH - S. Haug, SL - S. Liss. (Source: Alaska Division of Geological & Geophysical Surveys)

    Unique sample number designated by the author(s).

    SYMBOL
    Point symbols for types of bedding and foliation orientation data (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    1Strike and dip direction of beds
    3Strike and dip direction of beds, top of beds known from sedimentary features
    4Strike and dip direction of overturned beds
    5Strike of vertical beds, stratigraphic tops to north
    7Bearing of plunge of lineation
    9Strike and dip direction of foliation
    12Strike and dip direction of cleavage
    13Strike of vertical cleavage
    19Strike and dip direction of joints
    20Strike of vertical joints

    ANGLE
    Strike of plane using "Right-hand rule," where north is 0 and degrees increase clockwise to 360, always 90 degrees counter-clockwise from dip direction (Source: Alaska Division of Geological & Geophysical Surveys)

    Range of values
    Minimum:3
    Maximum:360
    Units:degrees

    DIPANGLE
    Degrees that a plane is inclined relative to horizontal, horizontal being 0 degrees, vertical being 90 degrees; always 90 degrees clockwise from strike (Source: Alaska Division of Geological & Geophysical Surveys)

    Range of values
    Minimum:10
    Maximum:90
    Units:degrees

    SHOW
    Indicates whether or not the point is printed on the published paper map (Source: Alaska Division of Geological & Geophysical Surveys)

    "Yes" - The point is printed or shown on the Preliminary Interpretive Geologic Bedrock Map of the Tanana A-1 and A-2 Quadrangles, Central Alaska (Publication PDF98-37B-SH1). "No" - The point is not printed or shown on the Preliminary Interpretive Geologic Bedrock Map of the Tanana A-1 and A-2 Quadrangles, Central Alaska (Publication PDF98-37B-SH1). A value of "No" may indicate that a duplicate value was measured nearby or the point was simply omitted at the discretion of the author(s).


Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

    Funding for the geologic mapping and geochronologic dating performed for this project was provided by the U.S. Geological Survey STATEMAP Program under award number 03HQAG0055 and by the Alaska State Legislature.

  3. To whom should users address questions about the data?

    State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys
    GIS Data Manager/Cartographer
    3354 College Road
    Fairbanks, AK 99709-3707

    (907) 451-5029 (voice)
    (907) 451-5050 (FAX)
    dggspubs@alaska.gov

    Contact_Instructions:
    You may view our web site at <http://www.dggs.dnr.state.ak.us> for the latest information on available data. Please e-mail your questions and data requests when possible since our web site and e-mail address will remain current even if our phone number and mailing address change.


Why was the data set created?

The Tanana A-1 and A-2 quadrangles lie between the villages of Rampart, on the Yukon River, and Manley Hot Springs, at the terminus of the Elliott Highway. At the time the report was published, the area towns were not part of any municipal or local governmental jurisdiction. The investigation of gold, tin, and other mineral occurrences in conjunction with comprehensive geologic mapping and recently-acquired geophysical data will provide a scientific basis for expanded mineral exploration and development that can lead to the economic growth and the creation of new jobs needed by the Rampart-Manley-Tofty region's inhabitants and the State of Alaska. These objectives are consistent with the statewide goals and priorities articulated for the Department of Natural Resources by Alaska's Governor in his Executive Budget Summary for Fiscal Year 1997.


How was the data set created?

  1. From what previous works were the data drawn?

    Eakin, 1912 (source 1 of 6)
    Eakin, H.M., 1912, The Rampart and Hot Springs regions: U.S. Geological Survey Bulletin Bulletin 520, U.S. Geological Survey, Reston, VA, USA.

    Other_Citation_Details: p. 271-286
    Type_of_Source_Media: paper
    Source_Contribution:
    This map contains geologic unit descriptions and outcrop locations and was used to plan traverses and help define geologic units.

    Eakin, 1913 (source 2 of 6)
    Eakin, H.M., 1913, A geologic reconnaissance of a part of the Rampart Quadrangle, Alaska: U.S. Geological Survey Bulletin Bulletin 535, U.S. Geological Survey, Reston, VA, USA.

    Other_Citation_Details: p. 38
    Type_of_Source_Media: paper
    Source_Contribution:
    This map contains geologic unit descriptions and outcrop locations and was used to plan traverses and help define geologic units.

    Hopkins and Taber, 1962 (source 3 of 6)
    Hopkins, D.M., and Taber, B., 1962, Asymmetrical valleys in central Alaska (abs.): Special Paper v. 68, Geological Society of America, Boulder, CO, USA.

    Other_Citation_Details: p. 116
    Type_of_Source_Media: paper
    Source_Contribution:
    This map contains geologic unit descriptions and outcrop locations and was used to plan traverses and help define geologic units.

    Newberry and Clautice, 1997 (source 4 of 6)
    Newberry, R.J., and Clautice, K.H., 1997, Compositions of placer gold in the Rampart-Eureka-Manley-Tofty area, eastern Tanana and western Livengood quadrangles, central Interior Alaska, determined by electron microprobe analysis: Public Data File PDF 97-49, State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (DGGS), Fairbanks, AK, USA.

    Online Links:

    Other_Citation_Details: p. 49
    Type_of_Source_Media: paper
    Source_Contribution:
    This report contains information that was used to aid in the creation of and sample preparation for the surficial geologic map (PDF 98-37C).

    Wagner, 1957 (source 5 of 6)
    Wagner, A.A., 1957, The use of the Unified Soil Classification System by the Bureau of Reclamation: Proceedings v. I, 4th International Conference on Soil Mechanics and Foundation Engineering, London, England.

    Other_Citation_Details: p. 125
    Type_of_Source_Media: paper
    Source_Contribution:
    This report contains information that was used to aid in the creation of and sample preparation for the surficial and geologic materials map (PDF 98-37C and PDF 98-37D).

    Yeend, 1989 (source 6 of 6)
    Yeend, W.E., 1989, Gold placers, geomorphology, and paleo-drainage of Eureka Creek and Tofty areas, Alaska: U.S. Geological Survey Bulletin Bulletin 1946, U.S. Geological Survey, Reston, VA, USA.

    Other_Citation_Details: p. 107-109
    Type_of_Source_Media: paper
    Source_Contribution:
    This report contains information that was used to aid in the creation of and sample preparation for the surficial geologic map (PDF 98-37C).

  2. How were the data generated, processed, and modified?

    Date: 1997 (process 1 of 5)
    Field work - Field work for bedrock investigations, including ridge traverses and examination of riverbank exposures, was conducted between June 16 and July 8, 1997. Field notes and rock samples were collected at approximately 700 stations throughout the Tanana A-1 and A-2 Quadrangles. Bedrock mappers recorded observations on 1:50,000- and 1:63,360-scale topographic base maps, compiled onto a 1:50,000-scale mylar map after the field season ended. Field stations were located using hand held GPS units. Field station notes and GPS location data were manually entered into a spreadsheet.

    Date: 1997 (process 2 of 5)
    Fieldwork - Fieldwork for surficial geologic investigations, including ridge and valley traverses, road cut investigations, and river exposures, was conducted for approximately 21 person-days in June and July 1997 by a surficial geologist. Field notes and sediment samples were collected throughout the area for surficial investigations. Surficial mapping involved using sources cited below on a regular basis for checking and correlating general units. The surficial mapper recorded observations on co-registered acetate overlays on 1:50,000-scale (nominal) color-infrared aerial photographs, and directly on 1:63,360-scale topographic base maps. Stations were located using air photos and topographic maps.

    Data sources used in this process:

    • Eakin, 1912
    • Eakin, 1913
    • Hopkins and Taber, 1962
    • Newberry and Clautice, 1997
    • Yeend, 1989

    Date: 1997 (process 3 of 5)
    Laboratory data - See paper reports PDF 98-37A and PDF 98-37B for more information.

    Date: 1997 (process 4 of 5)
    Photo interpretation - Before, during, and after field work, surficial-geologic information was interpreted using 1:50,000-scale (nominal) color-infrared air-photo stereopairs, and compiled onto acetate overlays. Photo interpretation was based on field notes from fieldwork process step (above), observed land forms and relationships in the photos, and all known geologic data from previous work in the area. The main sources of existing data include Eakin (1912; 1913), Hopkins and Tabor (1962), and Yeend (1989). The overlay information was transferred to a paper 1:63,360-scale USGS topographic base using a zoom transfer scope.

    Data sources used in this process:

    • Eakin, 1912
    • Eakin, 1913
    • Hopkins and Taber, 1962
    • Newberry and Clautice, 1997
    • Yeend, 1989

    Date: 1997 (process 5 of 5)
    Digital Cartography - Surficial-geologic information was digitized from the paper USGS topographic base map into Arc/Info 7.0.4 GIS (ArcEdit module) using a large-format digitizing table. Surficial-geologic polygons and lines were then edited and attributed using Arc, Info, and ArcEdit. Bedrock point data of locations of structural observations (strike, dip, cleavage, jointing, etc.) were intersected with the surficial-geologic polygon coverage using the Arc command "intersect" in order to identify locations that were mapped as surficial materials based on aerial photography but were found to have small exposures that were desirable to be mapped as bedrock. These areas were then modified in the surficial-geologic coverages to be areas of bedrock exposure. Final bedrock and surficial geology polygon coverages were merged using the Arc command "union" to generate the polygon coverage used to make the comprehensive geologic map. Other cartographic elements, primarily text and tables, were created in CorelDraw, converted to CGM format, and imported into ArcPlot for final layout. Data from the comprehensive geologic map of the area were used as the basis for generating the derivative engineering-geologic map. An ArcInfo lookup table was made to assign geologic units (item UNIT) from the comprehensive map to appropriate engineering-geologic units (item MAT) based on the Unified Soil Classification System as described by Wagner (1957). This lookup table was applied to the ArcInfo polygon coverage containing the geologic units and a new engineering-geologic polygon coverage was generated using the "dissolve" command based on the new materials-unit item "MAT." Additional features were mapped from ground observations and interpretation of air photos, and digitized and attributed using ArcInfo. ArcPlot was used to generate plot files of the resulting materials coverage using DGGS-standard symbology.

    Data sources used in this process:

    • Wagner, 1957

  3. What similar or related data should the user be aware of?

    Reifenstuhl, R.R., Dover, J.H., Newberry, R.J., Clautice, K.H., Liss, S.A., Blodgett, R.B., and Weber, F.R., 1998, Interpretive geologic bedrock map of the Tanana A-1 and A-2 quadrangles, central Alaska: Public Data File PDF 98-37B, State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (DGGS), Fairbanks, AK, USA.

    Online Links:

    Other_Citation_Details: 17 p., 1 sheet, scale 1:63,360
    Pinney, D.S., 1998, Surficial geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Public Data File PDF 98-37C, State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys, Fairbanks, AK, USA.

    Online Links:

    Other_Citation_Details: 1 sheet, scale 1:63,360
    Pinney, D.S., 1998, Derivative engineering geologic map of the Tanana A-1 and A-2 quadrangles, central Alaska: Public Data File PDF 98-37D, State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys, Fairbanks, AK, USA.

    Online Links:

    Other_Citation_Details: 1 sheet, scale 1:63,360


How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

    Location data for geologic and comprehensive point data were entered manually from GPS units into a spreadsheet. Data for surficial and materials point, line, and polygon data were determined in the field using 1:63,360-scale topographic maps and 1:50,000 (nominal) scale, color-infrared aerial photographs. Geologic data included in the compilation are the field maps and notes from this project as well as data from other sources as noted in the "Sources Cited" section. Attributes were verified for consistency and completeness during the creation of the metadata.

  2. How accurate are the geographic locations?

    DGGS location data and estimated position errors were manually entered into a spreadsheet. Sample numbers and locations with selected data were spatially registered and analyzed in ArcGIS software. Location data for the surficial and materials maps were determined visually using topographic maps at a scale of 1:63,360 and 1:50,000 (nominal) scale, color-infrared aerial photographs. See "Source_Information" section for horizontal positional accuracy of locations not measured by DGGS.

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    This dataset includes geospatial information about geologic units, their ages, field sample locations, structural features, structural measurements, and geology interpreted from airborne geophysics.

  5. How consistent are the relationships among the observations, including topology?

    Polygon topology present and clean on appropriate data. Other data are line, point, or annotation data and do not require topologic relationships.


How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints:
This report, map, and/or dataset are available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below).
Use_Constraints:
Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. User specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys.

  1. Who distributes the data set? (Distributor 1 of 1)

    State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys
    Natural Resource Technician
    3354 College Road
    Fairbanks, AK 99709-3707
    USA

    907-451-5020 (voice)
    907-451-5050 (FAX)
    dggspubs@alaska.gov

    Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
    Contact_Instructions:
    Please view our web site (<http://www.dggs.dnr.state.ak.us>) for the latest information on available data. Please contact us using the e-mail address provided above when possible.
  2. What's the catalog number I need to order this data set?

    Public Data File 98-37A v 1.1

  3. What legal disclaimers am I supposed to read?

    The State of Alaska makes no express or implied warranties (including warranties of merchantability and fitness) with respect to the character, function, or capabilities of the electronic services or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products, any failure thereof, or otherwise, and in no event will the State of Alaska's liability to the requester or anyone else exceed the fee paid for the electronic service or product.

  4. How can I download or order the data?

  5. What hardware or software do I need in order to use the data set?

    Please check the MapInfo web site (<http://www.mapinfo.com/>) for the latest documentation on importing ESRI shape files.


Who wrote the metadata?

Dates:
Last modified: 06-May-2008
Last Reviewed: 06-May-2008
To be reviewed: 21-Mar-2009
Metadata author:
State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys
Metadata Manager
3354 College Road
Fairbanks, AK 99709-3707
USA

907-451-5039 (voice)
907-451-5050 (FAX)
dggspubs@alaska.gov

Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays.
Contact_Instructions:
Please contact us through the e-mail address above whenever possible.
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)


Generated by mp version 2.9.6 on Tue May 06 14:29:35 2008