Northeast Tanacross geologic map and map units and descriptions

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Frequently anticipated questions:

What does this data set describe?

Title: Northeast Tanacross geologic map and map units and descriptions
Abstract:
Report of Investigation 2020-9B, Northeast Tanacross geologic map and map units and descriptions, provides 500 square miles of 1:63,360-scale geologic mapping in the northeastern Tanacross Quadrangle (Tanacross D-1, and parts of the C-1, C-2, and D-2 quadrangles), located 15 miles southeast of Chicken, Alaska. The project took place during two periods: a reconnaissance mapping effort June 12-22, 2017, and a detailed campaign June 18-July 16, 2018. The map area covers the boundary between the allochthonous Yukon-Tanana terrane (YTT) and the parautochthonous North American margin (pNA) from which the YTT initially rifted. This suture zone has a complex, multiphase structural and metamorphic history, and the northeastern Tanacross Quadrangle is one of the rare areas in which it is exposed. The conceptual framework has been developed in the literature, but it is not fully represented in previously published geologic maps of eastern Alaska. This map encompasses an area of current mineral industry interest; it includes the Taurus porphyry copper-gold-molybdenum +/- rhenium deposit and several other occurrence types, including gold, copper, and molybdenum in porphyritic intrusions, structurally controlled silver-lead-zinc prospects, and placer gold deposits. The complete report, geodatabase, and ESRI fonts and style files are available from the DGGS website: http://doi.org/10.14509/30539.
Supplemental_Information:
This geodatabase is organized according to the AK GeMS mapping schema Hendricks, M.D., Ekberg, P.G., Athey, J.E., Wyatt, W.C., Willingham, A.L., and Naibert, T.J., 2021, AK GeMS data dictionary: A description of the Alaska geologic mapping schema: Alaska Division of Geological & Geophysical Surveys Miscellaneous Publication 170, 10 p. https://doi.org/10.14509/30669. The distribution package includes ESRI fonts and style files, along with usage instructions. Further documentation of the symbology is provided by Ekberg, P.G., Hendricks, M.D., and Athey, J.E., 2021, AK GeMS symbology: A description of the AK GeMS style file: Alaska Division of Geological & Geophysical Surveys Miscellaneous Publication 169, 7 p. https://doi.org/10.14509/30584
  1. How might this data set be cited?
    Wypych, Alicja, Hubbard, T.D., Naibert, T.J., Athey, J.E., Newberry, R.J., Sicard, K.R., Twelker, Evan, Werdon, M.B., Willingham, A.L., Wyatt, W.C., and Lockett, A.C., 2021, Northeast Tanacross geologic map and map units and descriptions: Report of Investigation RI 2020-9B, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: p. 9-26, 1 sheet, scale 1:63,360
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -141.653213
    East_Bounding_Coordinate: -141.000000
    North_Bounding_Coordinate: 64.001478
    South_Bounding_Coordinate: 63.612549
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 2017
    Ending_Date: 2018
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: geodatabase
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a vector data set.
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 7
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -141
      Latitude_of_Projection_Origin: 0
      False_Easting: 500000.000000
      False_Northing: 0
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest .00000001
      Ordinates (y-coordinates) are specified to the nearest .00000001
      Planar coordinates are specified in Meters
      The horizontal datum used is NAD83.
      The ellipsoid used is GRS 80.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257222101000025.
  7. How does the data set describe geographic features?
    ne_tanacross_ak_gems_db_pkg
    Geodatabase, layer files, style files, and fonts (Source: Alaska Division of Geological & Geophysical Surveys)
    ne_tanacross_gems_db_pkg
    Geodatabase, layer files, style files, and fonts (Source: Alaska Division of Geological & Geophysical Surveys)
    ne_tanacross_gems_shapefile_pkg
    Shapefiles and open data files (Source: Alaska Division of Geological & Geophysical Surveys)

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
  2. Who also contributed to the data set?
    We would like to thank James V. Jones III (USGS, Anchorage) and Robert Gillis (DGGS) for thorough and constructive reviews of the geologic map, map unit descriptions, and report. The DGGS Northeast Tanacross project was funded by the USGS National Cooperative Geologic Mapping Program under STATEMAP award number G18AC00137 for 2018 and by State of Alaska general funds. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government.
  3. To whom should users address questions about the data?
    Alaska Division of Geological & Geophysical Surveys
    Metadata Manager
    3354 College Road
    Fairbanks, AK
    USA

    (907)451-5020 (voice)
    (907)451-5050 (FAX)
    dggspubs@alaska.gov
    Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
    Contact_Instructions:
    Please view our website (https://www.dggs.alaska.gov) for the latest information on available data. Please contact us using the e-mail address provided above when possible.

Why was the data set created?

Resurgent mineral industry interest in the East central Alaska region prompted DGGS to conduct new 1:63,360-scale geologic mapping in the northeastern Tanacross Quadrangle.

How was the data set created?

  1. From what previous works were the data drawn?
    Aleinikoff, J.N. and others, 1986 (source 1 of 16)
    Aleinikoff, J.N., Dusel-Bacon, Cynthia, and Foster, H.L., 1986, Geochronology of augen gneiss and related rocks, Yukon-Tanana terrane, east-central Alaska: Bulletin v. 97, no. 5, Geological Society of America, Unknown.

    Online Links:

    Type_of_Source_Media: paper
    Source_Contribution: Geologic map compilation
    Burns, L.E. and others, 2011 (source 2 of 16)
    Burns, L.E., Fugro Airborne Surveys Corp., and Fugro GeoServices, Inc., 2011, Ladue survey area: Magnetic and electromagnetic line, grid, and vector data and Maps, Fortymile mining district, Tanacross Quadrangle, eastern Alaska: Geophysical Report GPR 2011-1, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 26 sheets, scale 1:63,360, 1 DVD
    Type_of_Source_Media: paper
    Source_Scale_Denominator: 63360
    Source_Contribution: Geologic map compilation
    Burns, L.E. and others, 2015 (source 3 of 16)
    Burns, L.E., Geoterrex-Dighem, Stevens Exploration Management Corp., Emond, A.M., and Graham, G.R.C., 2015, Fortymile mining district electromagnetic and magnetic airborne geophysical survey data compilation: Geophysical Report GPR 2015-4, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 12 p
    Type_of_Source_Media: paper
    Source_Contribution: Geologic map compilation
    Dusel-Bacon, Cynthia and others, 2006, p. 25-74 (source 4 of 16)
    Dusel-Bacon, Cynthia, Hopkins, M.J., Mortensen, J.K., Dashevsky, S.S., Bressler, J.R., and Day, W.C., 2006, Paleozoic tectonic and metallogenic evolution of the pericratonic rocks of east-central Alaska and adjacent Yukon: Special Paper 45, Geological Association of Canada, Unknown.

    Online Links:

    • null

    Type_of_Source_Media: paper
    Source_Contribution: Geologic map compilation
    Dusel-Bacon, Cynthia and Aleinikoff, J.N., 1996, p. 131-141 (source 5 of 16)
    Dusel-Bacon, Cynthia, and Aleinikoff, J.N., 1996, U-Pb zircon and titanite ages for augen gneiss from the Divide Mountain area, eastern Yukon-Tanana Upland, Alaska, and evidence for the composite nature of the Fiftymile Batholith: Bulletin B 2152, U.S. Geological Survey, United States.

    Online Links:

    Other_Citation_Details: p. 131-141
    Type_of_Source_Media: paper
    Source_Contribution: Geologic map compilation
    Ekberg, P.G. and others, 2021 (source 6 of 16)
    Ekberg, P.G., Hendricks, M.D., and Athey, J.E., 2021, AK GeMS symbology: A description of the AK GeMS style file: Miscellaneous Publication MP 169, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 7 p
    Type_of_Source_Media: paper
    Source_Contribution: GIS analysis and digital cartography
    Emond, A.M. and others, 2015 (source 7 of 16)
    Emond, A.M., CGG, Burns, L.E., Graham, G.R.C., and (US), CGG Land Inc., 2015, Tok electromagnetic and magnetic airborne geophysical survey data compilation: Geophysical Report GPR 2015-2, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 13 p
    Type_of_Source_Media: paper
    Source_Contribution: Geologic map compilation
    Flynn, R.L., 2003 (source 8 of 16)
    Flynn, R.L., 2003, Geology of the Boundary area, Eagle A-1 and Tanacross D-1 quadrangles, east-central Alaska: University of Alaska Fairbanks, Fairbanks, Alaska.

    Online Links:

    • null

    Type_of_Source_Media: paper
    Source_Contribution: Geologic map compilation
    Gill, R.D., 1977 (source 9 of 16)
    Gill, R.D., 1977, Geology and mineral deposits of the southwest quarter of the Tanacross D-1 Quadrangle, Alaska: Western Washington University, Bellingham, Washington.

    Online Links:

    • null

    Type_of_Source_Media: paper
    Source_Contribution: Geologic map compilation
    Hendricks, M.D. and others, 2021 (source 10 of 16)
    Hendricks, M.D., Ekberg, P.G., Athey, J.E., Wyatt, W.C., Willingham, A.L., and Naibert, T.J., 2021, AK GeMS data dictionary: A description of the Alaska geologic mapping schema: Miscellaneous Publication MP 170, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 10 p
    Type_of_Source_Media: paper
    Source_Contribution: GIS analysis and digital cartography
    Naibert, T.J. and others, 2018 (source 11 of 16)
    Naibert, T.J., Benowitz, J.A., Wypych, Alicja, Sicard, K.R., and Twelker, Evan, 2018, 40Ar/39Ar data from the Tanacross D-1 and D-2, Big Delta B-4 and B-5, and Mount Hayes A-6 quadrangles, Alaska: Raw Data File RDF 2018-3, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 15 p
    Type_of_Source_Media: paper
    Source_Contribution: Geologic map compilation
    Szumigala, D.J. and others, 2002 (source 12 of 16)
    Szumigala, D.J., Newberry, R.J., Werdon, M.B., Athey, J.E., Flynn, R.L., and Clautice, K.H., 2002, Bedrock geologic map of the Eagle A-1 Quadrangle, Fortymile mining district: Preliminary Interpretive Report PIR 2002-1B, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 sheet, scale 1:63,360
    Type_of_Source_Media: paper
    Source_Scale_Denominator: 63360
    Source_Contribution: Geologic map compilation
    Todd, Erin and others, 2019 (source 13 of 16)
    Todd, Erin, Wypych, Alicja, and Kylander-Clark, Andrew, 2019, U-Pb and Lu-Hf isotope, age, and trace element data from zircon separates from the Tanacross D-1, and parts of D-2, C-1, and C-2 quadrangles: Raw Data File RDF 2019-5, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 10 p
    Type_of_Source_Media: paper
    Source_Contribution: Geologic map compilation
    Werdon, M.B. and others, 2001 (source 14 of 16)
    Werdon, M.B., Newberry, R.J., and Szumigala, D.J., 2001, Bedrock geologic map of the Eagle A-2 Quadrangle, Fortymile mining district, Alaska: Preliminary Interpretive Report PIR 2001-3B, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 sheet, scale 1:63,360
    Type_of_Source_Media: paper
    Source_Scale_Denominator: 63360
    Source_Contribution: Geologic map compilation
    Wypych, Alicja and others, 2019 (source 15 of 16)
    Wypych, Alicja, Hubbard, T.D., Naibert, T.J., Athey, J.E., Newberry, R.J., Sicard, K.R., Twelker, Evan, Werdon, M.B., Willingham, A.L., Wyatt, W.C., and Lockett, A.C., 2019, Northeastern Tanacross geologic map, Tanacross D-1, D-2, C-1, and C-2 quadrangles, Alaska: Preliminary Interpretive Report PIR 2019-6, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 20 p., 1 sheet, scale 1:63,360
    Type_of_Source_Media: paper
    Source_Scale_Denominator: 63360
    Source_Contribution: Geologic map compilation
    U.S. Geological Survey National Cooperative Geologic Mapping Program, 2020 (source 16 of 16)
    U.S. Geological Survey National Cooperative Geologic Mapping Program, 2020, GeMS (Geologic Map Schema) - A standard format for the digital publication of geologic maps: Techniques and Methods TM 11-B10, U.S. Geological Survey, United States.

    Online Links:

    Other_Citation_Details: 1 p
    Type_of_Source_Media: paper
    Source_Contribution: GIS analysis and digital cartography
  2. How were the data generated, processed, and modified?
    Date: 2018 (process 1 of 6)
    Quaternary unconsolidated deposits - This map includes unconsolidated surficial deposits in the Tanacross D-1 Quadrangle, the eastern one-third of the Tanacross D-2 Quadrangle, the northern half of the Tanacross B-2 Quadrangle, and the northeastern one-third of the Tanacross B-2 Quadrangle. To create this map we incorporated (1) geologic information from previous geologic mapping and published literature, (2) new interpretations using remotely sensed imagery, and (3) information gathered from limited field investigations. Previous geologic mapping of the unconsolidated deposits in the Tanacross Quadrangle includes work by Foster (1970) at a scale of 1:250,000, which provided a framework for our mapping and was instrumental in understanding the regional distribution and character of Quaternary deposits. Weber (1986) described the glacial history of the Yukon Tanana Upland and gave detailed descriptions of the extent and character of these deposits. Her work, along with glacial limits mapped by Péwé and others (1967) helped us identify and map glacial deposits in the map area. Work by Pinney (2001) and Stevens and Burns (2010) in the Eagle A-1 and A-2 quadrangles enabled us to understand the distribution and character of deposits in adjoining areas to the north and enhanced our understanding of the morphology and distribution of alluvial terraces, many of which are gold-bearing and extend southward into this map area. Mapping at a scale of 1:50,000 in the adjoining Borden Creek and Crag Mountain quadrangles by Jackson (2005a, 2005b) allowed comparisons with the distribution and character of deposits in Canada. A complete reference list is available in the accompanying report.
    Date: 2018 (process 2 of 6)
    Remotely sensed imagery - Surficial geology was mapped by interpreting 2.5-m-resolution SPOT 5 color-infrared and natural color red-green-blue (RGB) imagery (©2013, Distribution SpotImage S.A., SICORP, USA, all rights reserved) collected in 2009 and 2010 and stereoscopic pairs of approximately 1:65,000-scale, false-color, infrared aerial photographs taken in 1978 and 1981. SPOT 5 imagery was interpreted in ArcGIS Pro by overlaying it on hillshade and slopeshade images derived from Interferometric Synthetic Aperture Radar (IFSAR) bare-earth digital-elevation models (DEMs) created using data collected in 2010. By using the pseudo-3-D functionality of ArcGIS Pro and adjusting the transparency of the SPOT 5 imagery and the transparency and color of hillshade and slopeshade images, we were able to visualize subtle differences in features and identify geologic landforms. We used aerial photographs to identify geologic features and check our interpretations. Geospatial polygon features that represent geologic units were drawn using onscreen digitizing techniques in ArcGIS Pro.
    Date: 2018 (process 3 of 6)
    Geologic mapping - Fieldwork for bedrock investigations, including ridge traverses and examination of riverbank exposures, took place during two periods: a reconnaissance mapping effort June 12-22, 2017, and a detailed campaign June 18-July 16, 2018. Field notes, magnetic measurements, and rock samples were compiled and collected throughout the map area. Mappers recorded observations on 1:50,000- and 1:63,360-scale topographic base maps and compiled using ArcGIS software. Location data were collected using GPS-enabled tablets (2017 Samsung Galaxy Tab A) running the ESRI Collector App.
    Date: 2018 (process 4 of 6)
    Laboratory data compilation - Selected samples were submitted for geochemical and geochronologic analysis. The results were used to further interpret rock units and the stratigraphic and structural history of the map area.
    Date: 2020 (process 5 of 6)
    Geologic map compilation - The conceptual framework for the regional geology relies heavily on preexisting literature. The map area is heavily vegitated; consequently, the map interpretation relies heavily on geochemical and geochronological findings, magnetic and electromagnetic survey data, and observations from rocks collected from pits dug into rocky colluvial deposits below surficial loess or sand. A comprehensive bibliographic reference list of prior work used to identify and delineate rock units and structural elements is provided in the accompanying report. The map and report received technical review and editing by several scientists familiar with the subject matter. The authors incorporated the reviewers' suggestions into the final draft when deemed appropriate. Data sources used in this process:
    • Aleinikoff, J.N. and others, 1986
    • Burns, L.E. and others, 2011
    • Burns, L.E. and others, 2015
    • Dusel-Bacon, Cynthia and others, 2006, p. 25-74
    • Dusel-Bacon, Cynthia and Aleinikoff, J.N., 1996, p. 131-141
    • Emond, A.M. and others, 2015
    • Flynn, R.L., 2003
    • Gill, R.D., 1977
    • Naibert, T.J. and others, 2018
    • Szumigala, D.J. and others, 2002
    • Todd, Erin and others, 2019
    • Werdon, M.B. and others, 2001
    • Wypych, Alicja and others, 2019
    Date: 2021 (process 6 of 6)
    GIS analysis and digital cartography - This data distribution package's geologic and geographic features were organized and attributed according to the AK GeMS geologic mapping schema. The data were then programmatically transformed to provide download options in three formats: (1) an AK GeMS data package that includes the complete AK GeMS database and associated files, (2) a GeMS data package that is a conversion of the AK GeMS database into the base GeMS standard published by the USGS, and (3) a shapefile data package that includes two simple shapefile representations of the data. Data sources used in this process:
    • Ekberg, P.G. and others, 2021
    • Hendricks, M.D. and others, 2021
    • U.S. Geological Survey National Cooperative Geologic Mapping Program, 2020
  3. What similar or related data should the user be aware of?
    Wypych, Alicja, 2021, Northeast Tanacross geologic mapping project, Alaska: Report of Investigation RI 2020-9, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 75 p

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

  1. How well have the observations been checked?
    This data release provides legacy geospatial data converted to the GeMS and AK GeMS specifications. Attribute fields within each feature class are populated using corresponding applicable values from the GeMS and AK GeMS specifications. When known, certainty in attribute interpretation is indicated in the relevant fields. Attribute accuracy varies throughout the map and is scale-dependent.
  2. How accurate are the geographic locations?
    This data release provides legacy geospatial data converted to the GeMS and AK GeMS specifications. To record the originating authors' degree of confidence in the location of features, the data include descriptive fields within each feature class and accompanying orientation and location confidence lookup tables. Certainty in feature boundaries or location varies throughout the map.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    This publication is part of a DGGS Report of Investigations (RI). An RI is the completed product of original research and analysis, and RIs use professional cartography and undergo rigorous peer review, editing, and revision.
  5. How consistent are the relationships among the observations, including topology?
    All polygon features were topologically validated according to specifications of the AK GeMS geologic mapping schema.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints:
This report, map, and/or dataset is 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. The 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. The State of Alaska makes no express or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data 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 or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.
  1. Who distributes the data set? (Distributor 1 of 1)
    Alaska Division of Geological & Geophysical Surveys
    Metadata Manager
    3354 College Road
    Fairbanks, AK
    USA

    (907)451-5020 (voice)
    (907)451-5050 (FAX)
    dggspubs@alaska.gov
    Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
    Contact_Instructions:
    Please view our website (https://www.dggs.alaska.gov) for the latest information on available data. Please contact us using the e-mail address provided above when possible.
  2. What's the catalog number I need to order this data set? RI 2020-9B
  3. What legal disclaimers am I supposed to read?
    The State of Alaska makes no expressed or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data 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 or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 15-Jan-2022
Metadata author:
Alaska Division of Geological & Geophysical Surveys
Attn: Simone Montayne
Metadata Manager
3354 College Road
Fairbanks, AK
USA

(907)451-5020 (voice)
(907)451-5050 (FAX)
dggspubs@alaska.gov
Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:
Generated by mp version 2.9.50 on Fri Jan 14 20:02:00 2022