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
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:
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.
| Value | Definition |
|---|---|
| Kwcv | Wilber 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. |
| Kwcs | Wilber 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. |
| KJwq | Wolverine 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. |
| KJws | Wolverine 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'). |
| TrPp | Conglomerate (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. |
| Mg | Globe 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. |
| Dl | Devonian 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. |
| Dc | Conglomerate (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. |
| Pzlca | Chert 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. |
| Pzlv | Volcanic 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. |
| Pzlo | Orum 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. |
| Ofc | Fossil 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. |
| PzPad | Dolostone 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. |
| PzPag | Greenstone-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. |
| PzPac | Cherty 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). |
| PzPwg | Siliciclastic 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. |
| Tg | Hot 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). |
| Kmzd | Monzodiorite- 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. |
| JRc | Carbonatite - (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. |
| Value | Definition |
|---|---|
| b | Exposed bedrock- bedrock with essentially no cover |
| bc | Thinly covered bedrock - bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris |
| Qaf | Alluvial 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. |
| Qa | Alluvium 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. |
| Qap | Alluvial 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. |
| Qas | Silty 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. |
| Qfp | Flood 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 |
| Qsf | Silt 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 |
| Qag | Old, 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 |
| Qac | Undifferentiated 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. |
| Qc | Undifferentiated 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 |
| Qca | Colluvial 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. |
| Qel | Loess - 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 |
| Qelp | Pitted 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 |
| Qer | Reworked 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 |
| Qld | Delta 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. |
| Qs | Swamp 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. |
| Qmt | Mine 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. |
| WATER | body of water |
| Value | Definition |
|---|---|
| Kwcv | Wilber 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. |
| Kwcs | Wilber 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. |
| KJwq | Wolverine 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. |
| KJws | Wolverine 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'). |
| TrPp | Conglomerate (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. |
| Mg | Globe 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. |
| Dl | Devonian 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. |
| Dc | Conglomerate (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. |
| Pzlca | Chert 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. |
| Pzlv | Volcanic 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. |
| Pzlo | Orum 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. |
| Ofc | Fossil 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. |
| PzPad | Dolostone 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. |
| PzPag | Greenstone - 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. |
| PzPac | Cherty 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). |
| PzPwg | Siliciclastic 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. |
| Tg | Hot 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). |
| Kmzd | Monzodiorite - 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. |
| Qaf | Alluvial 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. |
| Qa | Alluvium 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. |
| Qap | Alluvial 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 |
| Qas | Silty 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. |
| Qfp | Floodplain 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 |
| Qsf | Silt 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 |
| Qag | Old, 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 |
| Qac | Undifferentiated 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. |
| Qc | Undifferentiated 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 |
| Qca | Colluvial 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. |
| Qel | Loess - 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 |
| Qelp | Pitted 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 |
| Qer | Reworked 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 |
| Qld | Delta 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. |
| Qs | Swamp 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. |
| Qmt | Mine 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. |
| WATER | body of water |
| Value | Definition |
|---|---|
| GS | Fluvial 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. |
| GM | Poorly 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. |
| SM | Silt 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. |
| OR | Organic-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. |
| BC | Medium-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. |
| BG | Coarse-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. |
| BM | Medium-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. |
| BV | Medium-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. |
| BU | Rocks 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. |
| H20 | body of water |
| Value | Definition |
|---|---|
| FZONE | Kaltag 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. |
| Kwcq | Wilber 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). |
| Kdm | Mafic 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. |
| Kgs | Granite 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. |
| Ksy | Syenite 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. |
| Kmo | Monzonite - 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. |
| Pzum | Ultramafic 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. |
| Kwcv | Wilber 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. |
| Kwcs | Wilber 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. |
| KJwq | Wolverine 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. |
| KJws | Wolverine 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'). |
| TrPp | Conglomerate (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. |
| Dc | Conglomerate (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. |
| Pzlca | Chert 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. |
| Pzlv | Volcanic 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. |
| Pzlo | Orum 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. |
| PzPad | Dolostone 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. |
| PzPac | Cherty-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). |
| Tg | Hot 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). |
| Kmzd | Monzodiorite - 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. |
| JRc | Carbonatite (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. |
| Value | Definition |
|---|---|
| b | Exposed bedrock - Bedrock with essentially no cover |
| bc | Thinly covered bedrock - Bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris |
| Qaf | Alluvial 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. |
| Qa | Alluvium 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. |
| Qap | Alluvial 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 |
| Qas | Silty 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. |
| Qfp | Floodplain 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 |
| Qsf | Silt 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 |
| Qac | Undifferentiated 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. |
| Qc | Undifferentiated 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 |
| Qca | Colluvial 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. |
| Qel | Loess - 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 |
| Qelp | Pitted 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 |
| Qer | Reworked 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 |
| Qs | Swamp 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 |
| Qmt | Mine 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 |
| Value | Definition |
|---|---|
| Kwcs | Wilber 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. |
| KJwq | Wolverine 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. |
| KJws | Wolverine 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'). |
| TrPp | Conglomerate (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. |
| Dc | Conglomerate (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. |
| Pzlca | Chert 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. |
| Pzlv | Volcanic 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. |
| Pzlo | Orum 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. |
| PzPad | Dolostone 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. |
| PzPac | Cherty-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). |
| Tg | Hot 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). |
| Kmzd | Monzodiorite- 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. |
| Qaf | Alluvial 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. |
| Qa | Alluvium 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. |
| Qap | Alluvial 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 |
| Qas | Silty 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. |
| Qfp | Floodplain 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 |
| Qsf | Silt 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 |
| Qac | Undifferentiated 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. |
| Qc | Undifferentiated 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 |
| Qca | Colluvial 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. |
| Qel | Loess - 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 |
| Qelp | Pitted 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 |
| Qer | Reworked 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 |
| Qs | Swamp 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. |
| Qmt | Mine 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. |
| Kwcq | Wilber 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). |
| Kdm | Mafic 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. |
| Kgs | Granite 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. |
| Ksy | Syenite 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. |
| Kmo | Monzonite - 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. |
| Pzum | Ultramafic 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. |
| JRc | Carbonatite (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. |
| Value | Definition |
|---|---|
| GS | Fluvial 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. |
| GM | Poorly- 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. |
| SM | Silt 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. |
| OR | Organic-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. |
| BC | Medium-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. |
| BG | Coarse-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. |
| BM | Medium-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. |
| BO | Rocks 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. |
| BV | Medium-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. |
| BU | Rocks 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. |
| Value | Definition |
|---|---|
| b | Exposed bedrock - bedrock with essentially no cover |
| bc | Thinly covered bedrock - bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris |
| Qaf | Alluvial 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. |
| Qa | Alluvium 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. |
| Qap | Alluvial 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 |
| Qas | Silty 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. |
| Qfp | Floodplain 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 |
| Qsf | Silt 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 |
| Qag | Old, 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 |
| Qac | Undifferentiated 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. |
| Qc | Undifferentiated 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 |
| Qca | Colluvial 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. |
| Qel | Loess - 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 |
| Qelp | Pitted 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 |
| Qer | Reworked 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 |
| Qld | Delta 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. |
| Qs | Swamp 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. |
| Qmt | Mine 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. |
| nm | Not 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.*** |
| Value | Definition |
|---|---|
| HFELS | Hornfels 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. |
| Value | Definition |
|---|---|
| b | Exposed bedrock - bedrock with essentially no cover |
| bc | Thinly covered bedrock - bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris |
| Qaf | Alluvial 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. |
| Qa | Alluvium 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. |
| Qap | Alluvial 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 |
| Qas | Silty 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. |
| Qfp | Floodplain 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 |
| Qsf | Silt 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 |
| Qac | Undifferentiated 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. |
| Qc | Undifferentiated 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 |
| Qca | Colluvial 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. |
| Qel | Loess - 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 |
| Qelp | Pitted 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 |
| Qer | Reworked 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 |
| Qs | Swamp 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. |
| Qmt | Mine 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. |
| Value | Definition |
|---|---|
| HFELS | Hornfels 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. |
| NM | Not mapped, region is irrelevant and not meaningful for the particular data layer |
| Value | Definition |
|---|---|
| 0 | Hidden line, defines the polygon boundary, but is not displayed on the map for aesthetic purposes |
| 5 | Contact |
| 9 | Contact, concealed, generally buried beneath a mapped geologic unit, water, or ice |
| Value | Definition |
|---|---|
| b | Exposed bedrock - bedrock with essentially no cover |
| bc | Thinly covered bedrock - bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris |
| Qaf | Alluvial 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. |
| Qa | Alluvium 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. |
| Qap | Alluvial 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 |
| Qas | Silty 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. |
| Qfp | Floodplain 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 |
| Qsf | Silt 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 |
| Qag | Old, 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 |
| Qac | Undifferentiated 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. |
| Qc | Undifferentiated 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 |
| Qca | Colluvial 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. |
| Qel | Loess - 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 |
| Qelp | Pitted 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 |
| Qer | Reworked 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 |
| Qs | Swamp 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. |
| Qmt | Mine 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. |
| Value | Definition |
|---|---|
| 0 | Hidden line, defines the polygon boundary, but is not displayed on the map for aesthetic purposes |
| 5 | Contact |
| 9 | Contact, concealed, generally buried beneath a mapped geologic unit, water, or ice |
| Value | Definition |
|---|---|
| b | Exposed bedrock- bedrock with essentially no cover |
| bc | Thinly covered bedrock- bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris |
| Qaf | Alluvial 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. |
| Qa | Alluvium 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. |
| Qap | Alluvial 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 |
| Qas | Silty 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. |
| Qfp | Floodplain 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 |
| Qsf | Silt 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 |
| Qac | Undifferentiated 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. |
| Qc | Undifferentiated 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 |
| Qca | Colluvial 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. |
| Qel | Loess - 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 |
| Qelp | Pitted 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 |
| Qer | Reworked 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 |
| Qs | Swamp 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. |
| Qmt | Mine 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. |
| Value | Definition |
|---|---|
| 11 | Fault |
| 12 | Fault approximately located |
| 15 | Fault, 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.*** |
| 17 | Thrust 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 |
| 18 | Thrust 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 |
| 20 | Thrust 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 |
| 22 | Thrust 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 |
| Value | Definition |
|---|---|
| b | Exposed bedrock- bedrock with essentially no cover |
| bc | Thinly covered bedrock - bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris |
| Qaf | Alluvial 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. |
| Qa | Alluvium 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. |
| Qap | Alluvial 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 |
| Qas | Silty 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. |
| Qfp | Floodplain 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 |
| Qsf | Silt 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 |
| Qag | Old, 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 |
| Qac | Undifferentiated 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. |
| Qc | Undifferentiated 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 |
| Qca | Colluvial 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. |
| Qel | Loess - 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 |
| Qelp | Pitted 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 |
| Qer | Reworked 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 |
| Qs | Swamp 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. |
| Qmt | Mine 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. |
| Value | Definition |
|---|---|
| 11 | Fault |
| 12 | Fault approximately located |
| 15 | Fault, 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.*** |
| 17 | Thrust 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 |
| 18 | Thrust 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 |
| 22 | Thrust 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 |
| Value | Definition |
|---|---|
| b | Exposed bedrock - bedrock with essentially no cover |
| bc | Thinly covered bedrock - bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris |
| Qaf | Alluvial 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. |
| Qa | Alluvium 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. |
| Qap | Alluvial 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 |
| Qas | Silty 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. |
| Qfp | Floodplain 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 |
| Qsf | Silt 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 |
| Qac | Undifferentiated 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. |
| Qc | Undifferentiated 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 |
| Qca | Colluvial 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. |
| Qel | Loess - 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 |
| Qelp | Pitted 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 |
| Qer | Reworked 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 |
| Qs | Swamp 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. |
| Qmt | Mine 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. |
| Value | Definition |
|---|---|
| b | Exposed bedrock - bedrock with essentially no cover |
| bc | Thinly covered bedrock - bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris |
| Qaf | Alluvial 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. |
| Qa | Alluvium 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. |
| Qap | Alluvial 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 |
| Qas | Silty 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. |
| Qfp | Floodplain 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 |
| Qsf | Silt 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 |
| Qag | Old, 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 |
| Qac | Undifferentiated 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. |
| Qc | Undifferentiated 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 |
| Qca | Colluvial 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. |
| Qel | Loess - 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 |
| Qelp | Pitted 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 |
| Qer | Reworked 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 |
| Qld | Delta 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. |
| Qs | Swamp 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. |
| Qmt | Mine 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. |
| WATER | Body 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.*** |
| Value | Definition |
|---|---|
| b | Exposed bedrock - bedrock with essentially no cover |
| bc | Thinly covered bedrock - bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris |
| Qaf | Alluvial 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. |
| Qa | Alluvium 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. |
| Qap | Alluvial 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 |
| Qas | Silty 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. |
| Qfp | Floodplain 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 |
| Qsf | Silt 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 |
| Qac | Undifferentiated 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. |
| Qc | Undifferentiated 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 |
| Qca | Colluvial 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. |
| Qel | Loess - 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 |
| Qelp | Pitted 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 |
| Qer | Reworked 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 |
| Qs | Swamp 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. |
| Qmt | Mine 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. |
| Value | Definition |
|---|---|
| 22 | Anticline |
| 23 | Syncline |
| 27 | Overturned anticline, showing direction of dip of limbs |
| Value | Definition |
|---|---|
| 22 | Anticline |
| 23 | Syncline |
| 26 | Overturned syncline, showing direction of dip of limbs |
| Value | Definition |
|---|---|
| 4 | Generic line depicting a type of fold, anticline, syncline, or cross-section location |
| 34 | Fold 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). |
| 36 | Inferred 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). |
| 38 | Anticline 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). |
"Yes" - The line represents a cross-section. "No" - The line does not represent a cross-section.
| Value | Definition |
|---|---|
| b | Exposed bedrock - bedrock with essentially no cover |
| bc | Thinly covered bedrock - bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris |
| Qa | Alluvium 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. |
| Qap | Alluvial 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 |
| Qas | Silty 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. |
| Qfp | Floodplain 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 |
| Qsf | Silt 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 |
| Qag | Old, 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 |
| Qac | Undifferentiated 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. |
| Qc | Undifferentiated 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 |
| Qca | Colluvial 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. |
| Qel | Loess - 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 |
| Qelp | Pitted 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 |
| Qer | Reworked 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 |
| Qs | Swamp 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. |
| Qmt | Mine 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. |
| Value | Definition |
|---|---|
| 4 | Generic line depicting a type of fold, anticline, syncline, or cross-section location |
| 34 | Fold 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). |
| 36 | Inferred 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). |
| 38 | Anticline 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). |
"Yes" - The line represents a cross-section. "No" - The line does not represent a cross-section.
| Value | Definition |
|---|---|
| b | Exposed bedrock - bedrock with essentially no cover |
| bc | Thinly covered bedrock - bedrock covered by thin (generally less than 1 m thick) veneer of surficial debris |
| Qaf | Alluvial 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. |
| Qa | Alluvium 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. |
| Qap | Alluvial 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 |
| Qas | Silty 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. |
| Qfp | Floodplain 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 |
| Qsf | Silt 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 |
| Qac | Undifferentiated 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. |
| Qc | Undifferentiated 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 |
| Qca | Colluvial 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. |
| Qel | Loess - 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 |
| Qelp | Pitted 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 |
| Qer | Reworked 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 |
| Qs | Swamp 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. |
| Value | Definition |
|---|---|
| 0 | Hidden line, defines the polygon boundary, but is not displayed on the map for aesthetic purposes |
| 64 | Buried anomaly, boundary of airborne geophysical signature: high magnetics and low resistivity |
| Value | Definition |
|---|---|
| 0 | Hidden line, defines the polygon boundary, but is not displayed on the map for aesthetic purposes |
| 64 | Buried anomaly, boundary of airborne geophysical signature: high magnetics and low resistivity |
| 65 | Buried anomaly, boundary of airborne geophysical signature: low magnetics and high resistivity |
Unique sample number designated by the author(s).
| Value | Definition |
|---|---|
| 1 | Strike and dip direction of beds |
| 3 | Strike and dip direction of beds, top of beds known from sedimentary features |
| 4 | Strike and dip direction of overturned beds |
| 5 | Strike of vertical beds, stratigraphic tops to north |
| 7 | Bearing of plunge of lineation |
| 9 | Strike and dip direction of foliation |
| 12 | Strike and dip direction of cleavage |
| 13 | Strike of vertical cleavage |
| 19 | Strike and dip direction of joints |
| 20 | Strike of vertical joints |
| Range of values | |
|---|---|
| Minimum: | 3 |
| Maximum: | 360 |
| Units: | degrees |
| Range of values | |
|---|---|
| Minimum: | 10 |
| Maximum: | 90 |
| Units: | degrees |
"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).
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.
(907) 451-5029 (voice)
(907) 451-5050 (FAX)
dggspubs@alaska.gov
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.
Eakin, H.M., 1912, The Rampart and Hot Springs regions: U.S. Geological Survey Bulletin Bulletin 520, U.S. Geological Survey, Reston, VA, USA.
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.
Hopkins, D.M., and Taber, B., 1962, Asymmetrical valleys in central Alaska (abs.): Special Paper v. 68, Geological Society of America, Boulder, CO, USA.
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:
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.
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.
Data sources used in this process:
Data sources used in this process:
Data sources used in this process:
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:
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:
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:
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.
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.
This dataset includes geospatial information about geologic units, their ages, field sample locations, structural features, structural measurements, and geology interpreted from airborne geophysics.
Polygon topology present and clean on appropriate data. Other data are line, point, or annotation data and do not require topologic relationships.
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.
907-451-5020 (voice)
907-451-5050 (FAX)
dggspubs@alaska.gov
Public Data File 98-37A v 1.1
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.
Current publication is available on paper. To purchase this or other printed reports and maps, contact DGGS by phone (907-451-5020), e-mail (dggspubs@alaska.gov), or fax (907-451-5050). Payment accepted: Cash, check, money order, VISA, or MasterCard.
Printed publication can be purchased for $15.00 (contact information below) plus shipping if mailed.
| Data format: | PDF (version 1.6) |
|---|---|
| Network links: |
<http://dx.doi.org/10.14509/1863> |
| Data format: | ArcGIS Shapefile (version ESRI ArcGIS 9.x) |
|---|---|
| Network links: |
<http://dx.doi.org/10.14509/1863> |
| Media you can order: |
CD-ROM
(format Joliet)
|
Digital files on CD-ROM are available for $10.00 (contact information below). No fees charged for downloaded files.
Order by phone (907-451-5020), e-mail (dggspubs@alaska.gov), or fax (907-451-5050). The DGGS web site (<http://www.dggs.alaska.gov/>) has a list of electronic data available and an order form that can be printed. Payment accepted: Cash, check, money order, VISA, or MasterCard.
Digital downloads: less than 30 minutes for most files. Offline CD/DVD-ROMs: 1-2 weeks unless special arrangements are made and an express fee is paid.
Please check the MapInfo web site (<http://www.mapinfo.com/>) for the latest documentation on importing ESRI shape files.
907-451-5039 (voice)
907-451-5050 (FAX)
dggspubs@alaska.gov