NEF_border Polygon of boundary outline of the mapped area. NEF_cirques Polylines showing headwalls of possible cirques. NEF_geology Polygons of surficial-geologic map units. NEF_photolinears Polylines showing photolinears. NEF_pingos Points showing locations of pingos.
Stevens, D.S.P., 20110630, Surficial-geologic map of the northern Fairbanks mining district, Circle Quadrangle, Alaska: Report of Investigations RI 2011-4, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska.Online Links:
Planar coordinates are encoded using coordinate pair
Abscissae (x-coordinates) are specified to the nearest 1
Ordinates (y-coordinates) are specified to the nearest 1
Planar coordinates are specified in meters
The horizontal datum used is North American Datum of 1927.
The ellipsoid used is Clarke 1866.
The semi-major axis of the ellipsoid used is 6378206.4.
The flattening of the ellipsoid used is 1/294.9786982.
| Value | Definition |
|---|---|
| b | EXPOSED BEDROCK Undifferentiated bedrock with essentially no cover |
| b' | THINLY COVERED BEDROCK Undifferentiated bedrock that is covered by a thin (generally less than 1 m thick) veneer of colluvium, drift, undifferentiated glacial or glaciofluvial deposits, or combinations of these deposits; cover is sufficiently thin that planar bedrock structures, such as joints, foliation, and bedding or glacier-scoured bedrock subcrops are reflected at the ground surface by linear and curvilinear shallow troughs and bands of moist ground or hydrophilic vegetation |
| Qa | ALLUVIUM, UNDIFFERENTIATED Elongate deposits of moderately to well-sorted, well-stratified, fluvial pebblecobble gravel, sand, and silt, with scattered to numerous boulders comprising channel and overbank deposits of generally small streams; medium to thick bedded, locally crossbedded, shows fining-upward cycles, and is locally auriferous; clasts generally rounded; extensive willowalder thickets grow on many Qa deposits in mature valley fills; unfrozen to discontinuously frozen with low to moderate ice contents; surface smooth to hummocky, except for local low scarps |
| Qaa | ALLUVIUM IN ACTIVE CHANNELS Chiefly well-sorted and well-stratified layers and lenses of pebble gravel, sand, and silt with rare to scattered cobbles comprising river bars subject to recurrent inundation by modern streams every 5 yr or less (Chapin and others, 2006); mapped extent is a function of river level (stage) and reflects the transitory extent of exposed river bars at the time the photographs were taken; in braided and anastomosing reaches, active channels typically shift positions from year to year and present channel locations may differ from locations on the 1979 and 1981 photography; active channel alluvium underlies upper stream bank and active stream channels and includes point-bar and meander-scroll deposits; composed dominantly of gravel and sand where stream is braided and anastomosing, and sand and silt bars where meandering; prone to liquefaction where fine grained, unfrozen and saturated; where braided, subject to formation of extensive, thick, seasonal stream icings (aufeis); generally unfrozen, except seasonally frozen to depth of frost penetration; shallow water table |
| Qaf | ALLUVIAL FAN DEPOSITS Fan-shaped deposits of poorly to moderately sorted gravel, sand, and silt with numerous cobbles and boulders in proximal zone deposited by streams where they emerge from mountain valleys onto lower-gradient surfaces; lithologies reflect bedrock of source area; in general, size of clasts decreases and degree of sorting increases downfan; typically mixed with debris-flow deposits in proximal part of fans; unfrozen to discontinuously frozen, except in fine-grained distal deposits, where permafrost may be shallow and continuous; ice contents low to moderate |
| Qai | ALLUVIUM IN INACTIVE CHANNELS Elongate deposits of moderately to well-sorted, well-stratified, fluvial gravel, sand, and silt with scattered to numerous boulders forming modern floodplains and associated low terraces that are subject to flooding at least once or twice every century (Mason and Begét, 1991; Chapin and others, 2006); medium to thick bedded, locally crossbedded, shows fining-upward cycles, and may be locally auriferous; clasts generally rounded; may be covered by several meters of overbank silty sand and sandy gravel; may reflect former channels and flow regimes; may include more than one channel level; overbank sequences include flood-related features, like natural levees, crevasse-splays near channels, and fine-grained back-levee swale deposits farther from channels; lower surfaces may be flooded during periods of extremely high stream discharge; generally unfrozen in younger areas and discontinuously frozen in older areas with low to moderate ice contents; surface typically well vegetated, smooth to hummocky with local low scarps and bogs |
| Qat | TERRACE ALLUVIUM, UNDIFFERENTIATED Elongate deposits of well-sorted, well-rounded to subrounded pebblecobble gravel and sand with trace to some silt and rare to numerous boulders forming stream terrace treads no longer subject to inundations by the stream that deposited the alluvium (Kreig and Reger, 1982); may include several levels and incorporate outwash alluvium; may be covered by several meters of organic sandy silt and silty sand; surface smooth, except for local low scarps; continuously to discontinuously frozen with low to moderate ice contents |
| Qat4 | TERRACE ALLUVIUM OF YOUNGEST AGE Elongate deposits of well-sorted, well-rounded to subrounded pebblecobble gravel and sand with trace to some silt and rare to numerous boulders forming stream terrace treads no longer subject to inundations by the stream that deposited the alluvium (Kreig and Reger, 1982); may include several levels; may be covered by up to a meter of organic sandy silt and silty sand; upper surface typically only a few meters above modern stream level; surface smooth, except for local low scarps; continuously to discontinuously frozen with low to moderate ice contents |
| Qat3 | TERRACE ALLUVIUM OF YOUNG-INTERMEDIATE AGE Elongate deposits of well-sorted, well-rounded to subrounded pebblecobble gravel and sand with trace to some silt and rare to numerous boulders forming stream terrace treads no longer subject to inundations by the stream that deposited the alluvium (Kreig and Reger, 1982); may include several levels; may be covered by several meters of organic sandy silt and silty sand; upper surface about 30-50 m above modern stream level along upper Chatanika River and lower Sourdough Creek; surface smooth, except for local low scarps; continuously to discontinuously frozen with low to moderate ice contents |
| Qat2 | TERRACE ALLUVIUM OF INTERMEDIATE AGE Elongate deposits of well-sorted, well-rounded to subrounded pebblecobble gravel and sand with trace to some silt and rare to numerous boulders forming stream terrace treads no longer subject to inundations by the stream that deposited the alluvium (Kreig and Reger, 1982); includes several levels; distribution and elevation of deposits suggest unit may incorporate outwash alluvium of Little Champion or Prindle glaciations, or both, of Weber and Hamilton (1987); largest measured cobbles up to 54 cm diameter; upper surfaces of some granite cobbles strongly weathered and decomposed, while undersides remain sound; may be covered by several meters of organic sandy silt and silty sand; upper surface about 90 m above modern stream level along upper Chatanika River and lower Sourdough Creek; surface smooth, except for local low scarps; continuously to discontinuously frozen with low to moderate ice contents |
| Qat1 | TERRACE ALLUVIUM OF OLDEST AGE Elongate deposits of well-sorted, well-rounded to subrounded pebblecobble gravel and sand with trace to some silt and rare to numerous boulders forming stream terrace treads no longer subject to inundations by the stream that deposited the alluvium (Kreig and Reger, 1982); includes several levels; distribution and elevation of deposits suggest unit probably incorporates outwash alluvium of Prindle glaciation or older of Weber and Hamilton (1987); commonly preserved as a thin veneer or gravel lag; upper surfaces of some granite cobbles strongly weathered and decomposed, while undersides remain sound; may be covered by several meters of organic sandy silt and silty sand; upper surface about 90-120 m above modern stream level along Faith Creek and about 180 m above modern stream level along upper Chatanika River; surface smooth, except for local low scarps; continuously to discontinuously frozen with low to moderate ice contents |
| Qat1? | POSSIBLE TERRACE ALLUVIUM OF OLDEST AGE Possible upstream continuation of unit Qat1 into upper reaches of Faith Creek and upslope of unit Qat2 along the Chatanika River at the mouth s of Faith and Sourdough creeks; mapped primarily on the basis of subtle slope breaks and smooth surface morphology along valley walls; upper surface about 120-180 m above modern stream level along upper Chatanika River and 90-120 m above modern stream level along Faith Creek |
| Qc | COLLUVIUM, UNDIFFERENTIATED 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, gravity-driven mass movements involving sliding, flowing, gelifluction, and frost creep of weathered bedrock and modified glacial drift; cobbles and boulders are scattered to numerous; on lower headwalls of cirques and upper walls of glaciated valleys includes talus aprons and steep fans built by snow avalanches and debris flows; may include thin residual deposits and lags of highly modified drift of ancient glaciations, particularly in the northern part of the map area; medium to thick bedded; generally unsorted to very poorly sorted; thickness is highly variable, with thickest deposits at the bases of slopes; locally washed by meltwater and slope runoff; surface disturbances, such as from excavation, may result in melting of permafrost and subsequent slumping and flowage; surface smooth, lobed, or terraced and, if deposit is thin, generally reflects morphologies of underlying materials; discontinuously to continuously frozen with low to moderate ice contents |
| Qcl? | POSSIBLE LANDSLIDE DEPOSIT Unsorted, unstratified mixture of gravel, sand and silt derived from adjacent unconsolidated deposits and bedrock and deposited at the base of slope by near-surface to deep creeping, flowing, and sliding of failed bedrock and unconsolidated surficial deposits; surface slightly irregular to hummocky |
| Qcf | MIXED COLLUVIUM AND ALLUVIUM Primarily fan-shaped or elongate, massive to poorly stratified, generally inorganic silt mixed with sandy angular to subangular pebble gravels derived from weathered bedrock uplands and deposited by debris flows and hyperconcentrated flows produced during brief, intense summer storms; colluvial processes dominate slightly over fluvial processes; contains numerous cobbles in glaciated terrain and angular to subangular, fresh to weathered rock fragments in weathered bedrock terrain; surface slightly irregular; discontinuously to continuously frozen with low to moderate ice contents |
| Qct | TALUS DEPOSITS Fans and aprons of coarse, angular, unsorted, frost-rived rock fragments downslope of bedrock outcrops with trace to some gravel, sand, and silt deposited on steep bedrock slopes by rock falls, snow avalanches, free fall, tumbling, rolling, and sliding; surface steep, slightly irregular, and covered with numerous rock fragments, particularly in distal zones; includes debris-flow tongues; unfrozen to discontinuously frozen with low ice contents |
| Qlc | LOWLAND COLLUVIUM Gravel, sand and silt derived from underlying or nearby bedrock and unconsolidated deposits and deposited in lowland areas adjacent to low-slope drainages primarily by mass-wasting processes; includes a component of primary and reworked eolian silt; overlies and incorporated into terrace deposits; surface smooth to gently sloping; discontinuously to continuously frozen with moderate to high ice contents |
| Qdlc | DRIFT OF LITTLE CHAMPION AGE Till associated with the Little Champion glaciation of Weber and Hamilton (1984); subrounded cobbles and boulders and some angular chips of schist and quartzite in a yellowish-brown matrix of silty sand (Rawlinson and Hickmott, 1987) deposited by glacial ice and reworked by meltwater streams; primary surface morphology largely obliterated due to post-depositional modification by weathering and slope processes; mapped by photo-interpretation at a single site in study area, at head of Hope Creek tributary drainage |
| Qdp | DRIFT OF PRINDLE AGE OR OLDER Till associated with the Prindle glaciation of Weber and Hamilton (1984) and possibly older glacial deposits; discontinuous to continuous sheets of heterogeneous pebble gravel with rare to numerous cobbles, boulders, and blocks up to 2 m in diameter in a brown matrix of sandy silt deposited directly from melting glacial ice and reworked by meltwater streams and mass-movement processes; generally thin, but locally up to 9.4 m thick; clasts generally subangular to subrounded; scattered angular pebbles; some small granite cobbles and pebbles are decomposing, but most are sound |
| Qdp? | Possible DRIFT OF PRINDLE AGE OR OLDER Till associated with the Prindle glaciation of Weber and Hamilton (1984) and possibly older glacial deposits; discontinuous to continuous sheets of heterogeneous pebble gravel with rare to numerous cobbles, boulders, and blocks up to 2 m in diameter in a brown matrix of sandy silt deposited directly from melting glacial ice and reworked by meltwater streams and mass-movement processes; generally thin, but locally up to 9.4 m thick; clasts generally subangular to subrounded; scattered angular pebbles; some small granite cobbles and pebbles are decomposing, but most are sound |
| Qh | CONSTRUCTION PAD Artificial fill of pebble-cobble gravel with trace to some sand and silt forming bases for DOT station; well to poorly sorted; surface smooth to irregular; extent based on distribution in August 1981 when the aerial photographs were taken |
| Qmt | MINE TAILINGS Water-washed pebblecobble gravel with trace to some sand and silt piled in active or formerly active gravel pits, open-pit mines, and dredged areas; typically well sorted; surface smooth to irregular or forming symmetrical ridges and cones; unfrozen |
| Range of values | |
|---|---|
| Minimum: | 65.2 |
| Maximum: | 65.3 |
| Units: | degrees |
| Range of values | |
|---|---|
| Minimum: | -146.5 |
| Maximum: | -146.0 |
| Units: | degrees |
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The purpose of this map is to show the distribution of unconsolidated geologic deposits and related features in the northern Fairbanks mining district.
Chapin, F.S., III, Viereck, L.A., Adams, P.C., Van Cleve, Keith, Fastie, C.L., Ott, R.A., Mann, Daniel,, and Johnson, J.F., 2006, Successional processes in the Alaskan boreal forest: Oxford University Press, New York.
Chapin, F.S., III (ed.), Oswood, M.W. (ed.), Van Cleve, Keith (ed.), Viereck, L.A. (ed.), and Verbyla, D.L. (ed.), 2006, Alaska's changing boreal forest: Oxford University Press, New York.
Kreig, R.A., and Reger, R.D., 1982, Air-photo analysis and summary of landform soil properties along the route of the Trans-Alaska Pipeline System: Geologic Report GR 66, Alaska Division of Geological & Geophysical Surveys, Alaska.
Mason, O.K., and Beget, J.E., 1991, Holocene flood history of the Tanana River, Alaska, U.S.A.: Arctic and Alpine Research v. 23, no. 4.
Rawlinson, S.E., and Hickmott, D.R., 1987, Surficial geology, lineaments, and placer resources in the Lime PeakMt. Prindle and Pinnell Mountain Trail areas, east-central Alaska: Miscellaneous Publication MP 29D, Alaska Division of Geological & Geophysical Surveys, Alaska.
Smith, T.E. (ed.), Pessel, G.H. (ed.), and Wiltse, M.A. (ed.), 1987, Mineral assessment of the Lime PeakMt. Prindle area, Alaska: Miscellaneous Publication MP 29D, Alaska Division of Geological & Geophysical Surveys, Alaska.
Weber, F.R., and Hamilton, T.D., 1984, Glacial geology of the Mt. Prindle area, YukonTanana upland, Alaska: Professional Report PR 86, Alaska Division of Geological & Geophysical Surveys, Alaska.
Alaska Division of Geological & Geophysical Surveys (ed.), 1984, Short notes on Alaskan geology: Professional Report PR 86, Alaska Division of Geological & Geophysical Surveys, Alaska.
Data sources used in this process:
Certainty in identification of the map units varies due to the scale and interpretive nature of the mapping. The geologic unit interpretations and boundaries presented in this report result from interpretation of nominal 1:65,000-scale aerial photographs taken in 1979 and 1981, investigative traverses throughout the map area, aerial reconnaissance via helicopter, and examination of road-cuts and river exposures. Surficial-geologic polygons and lines were edited and attributed using ArcGIS. This map has received two technical reviews by scientists familiar with the subject matter. We incorporated the reviewer's suggestions into the final draft.
Surficial-geologic map data has a horizontal positional accuracy dependent on: 1) the 1:65,000-scale (nominal) aerial photographs upon which the mapping was done, with an estimated potential error due to a pen line width of approximately 0.25 mm being equivalent to approximately 16.25 meters on the ground; and 2) the accuracy of the orthorectification of the aerial photographs, error magnitude highly variable and potentially large in areas of significant relief but generally has an RMS error of less than 4 pixels, equivalent to approximately 16.5 meters on the ground. Total potential horizontal error for surficial-geologic map features is therefore estimated to be up to 32.75 meters.
The data set utilizes field observations and air photo interpretations to locate and characterize the geologic unit extent and features. It includes geospatial information about units traceable on air photos at a scale of ~1:65000 and/or in the field.
Polygon topology is present and clean on the original geospatial dataset. All polygon features were topologically validated using ArcGIS prior to export to shapefile format.
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| Data format: | SHP |
|---|---|
| Network links: |
<http://dx.doi.org/10.14509/22642> |
| Data format: | |
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<http://dx.doi.org/10.14509/22642> |
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