Geologic map of the Racetrack Basin area, central North Slope, Alaska

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Frequently anticipated questions:


What does this data set describe?

Title:
Geologic map of the Racetrack Basin area, central North Slope, Alaska
Abstract:
Geologic map of the Racetrack Basin area, central North Slope, Alaska, Preliminary Interpretive Report 2025-6, presents a 1:63,360-scale interpretive bedrock geologic map of the Racetrack Basin area in the northeastern Chandler Lake quadrangle, northern Alaska. Covering approximately 675 km2 (~260 mi2), the map area includes prominent exposures of Brookian megasequence strata that record the infilling of the Colville foreland basin and the tectonic evolution of the Brooks Range. Fieldwork conducted in summer 2021 included observations at 267 localities during a helicopter-supported campaign. The resulting geologic map integrates sedimentologic, stratigraphic, and structural data to refine understanding of regional petroleum systems and basin architecture. Key outcomes of this study include recognition of previously abandoned members of the Schrader Bluff Formation and evaluation of stratigraphic thickness variability across the map area in the context of regional sequence-stratigraphic trends. The report also highlights the influence of Cretaceous depositional systems on mechanical stratigraphy and deformation, identifying paleo-shelf margins as critical transitions that affect fold geometry and distribution. This mapping effort contributes to a long-term DGGS initiative to produce a contiguous series of detailed geologic maps along the Brooks Range foothills, enhancing the geologic framework of northern Alaska. The dataset contains geologic, structural, stratigraphic, and geochronologic data organized according to the GeMS and AK GeMS mapping schemas. The complete report, geodatabase, and ESRI fonts and style files are available from the Alaska Division of Geological & Geophysical Surveys website: http://doi.org/10.14509/31723.
Supplemental_Information:
This geodatabase is organized according to the AK GeMS mapping schema Hendricks, M.D., Macpherson, A.E., Athey, J.E., Wyatt, W.C., Montayne, Simone, Buchanan, Wes, Rivera, P.G., and Steinleitner, A.M., 2024, AK GeMS data dictionary: A description of the Alaska geologic mapping schema: Alaska Division of Geological & Geophysical Surveys Miscellaneous Publication 170 v. 2, 13 p. https://doi.org/10.14509/31172. 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?
    Herriott, T.M., Wartes, M.A., Willingham, A.L., Gillis, R.J., and Qureshi, K.A., 2025, Geologic map of the Racetrack Basin area, central North Slope, Alaska: Preliminary Interpretive Report PIR 2025-6, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 sheet, scale 1:63,360
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -151.220185
    East_Bounding_Coordinate: -150.572793
    North_Bounding_Coordinate: 69.007360
    South_Bounding_Coordinate: 68.742572
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 2021
    Ending_Date: 2025
    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: 5
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -153
      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 1/298.257222101.
  7. How does the data set describe geographic features?
    racetrack_basin_ak_gems_db
    Geodatabase, layer files, style files, and fonts (Source: DGGS)
    racetrack_basin_gems_db
    Geodatabase, layer files, style files, and fonts (Source: DGGS)
    racetrack_basin_gems_geopackage
    SQLite Database file (Source: DGGS)
    racetrack_basin_gems_shapefile
    Shapefiles and open data files (Source: DGGS)

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?
    This geologic map was made possible through the collaborative efforts of several contributors. Geologic GIS data layers were developed by M.D. Hendricks (2019), A.L. Willingham (2019), A.E. Macpherson (2022), and K.A. Qureshi (2024, 2025). Cartographic design and layout were completed by A.E. Macpherson (2022) and K.A. Qureshi (2024, 2025). Ally M. Steinleitner implemented final database quality control and packaging. The map benefited from peer review by J.H. Long (2025), whose insights helped improve its clarity and accuracy. Funding was provided by the State of Alaska and the USGS National Cooperative Geologic Mapping Program under STATEMAP award number G21AC10706. 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?

The purpose of this research was to produce a detailed, 1:63,360-scale interpretive bedrock geologic map of the Racetrack Basin area in the northeastern Chandler Lake quadrangle, northern Alaska. The study aimed to refine the understanding of sedimentologic, stratigraphic, and structural relationships within Brookian megasequence strata, which recorded the evolution of the Colville foreland basin and Brooks Range. By documenting stratigraphic thickness variability and recognizing previously abandoned members of the Schrader Bluff Formation, the research contributed to regional sequence-stratigraphic interpretations and enhanced the geologic framework critical to petroleum systems analysis in northern Alaska.

How was the data set created?

  1. From what previous works were the data drawn?
    Ekberg, P.G. and others, 2021 (source 1 of 3)
    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
    Hendricks, M.D. and others, 2021 (source 2 of 3)
    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
    U.S. Geological Survey National Cooperative Geologic Mapping Program, 2020 (source 3 of 3)
    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: 2021 (process 1 of 2)
    Geologic mapping - DGGS geologists constructed a 1:63,360-scale interpretive bedrock geologic map of the Racetrack Basin area in the northeastern Chandler Lake quadrangle, northern Alaska. To support this effort, they conducted helicopter-supported fieldwork in summer 2021, collecting geologic observations at 267 localities across approximately 675 km2 (~260 mi2). The team documented lithologic characteristics, stratigraphic relationships, and structural features of Brookian megasequence strata, which record the infilling of the Colville foreland basin and the tectonic evolution of the Brooks Range. Using these data, the geologists delineated geologic unit boundaries, refined stratigraphic correlations, and interpreted structural geometry.
    Date: 2025 (process 2 of 2)
    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 legacy data were 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?
    Herriott, T.M., Wartes, M.A., Decker, P.L., Gillis, R.J., Shellenbaum, D.P., Willingham, A.L., and Mauel, D.J., 2018, Geologic map of the Umiat-Gubik area, central North Slope, Alaska: Report of Investigation RI 2018-6, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 55 p., 1 sheet, scale 1:63,360
    LePain, D.L., Kirkham, R.A., and Montayne, Simone, 2021, Measured stratigraphic section, Nanushuk Formation (Albian-Cenomanian), Nanushuk River (Rooftop Ridge), Alaska: Preliminary Interpretive Report PIR 2021-5, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 8 p., 1 sheet
    Herriott, T.M., Wartes, M.A., Gillis, R.J., Willingham, A.L., and Qureshi, K.A., 2025, Geologic map of the Rooftop Ridge area, central North Slope, Alaska: Preliminary Interpretive Report PIR 2025-5, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 sheet, scale 1:63,360

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

  1. How well have the observations been checked?
    Attribute fields within each feature class are populated using the map symbology and 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?
    Certainty in feature boundaries or location varies throughout the map. Data fields within each feature class and the accompanying orientation and location confidence lookup tables record the authors' degree of confidence in the location of applicable features.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    This publication is a DGGS Preliminary Interpretive Report (PIR). A PIR provides timely release of maps and reports with a preliminary interpretation of geology or analytical data. Several scientists familiar with the geology of map area reviewed this product for general readability and logical consistency, but it has not undergone technical peer review.
  5. How consistent are the relationships among the observations, including topology?
    All polygon features were topologically validated according to the AK GeMS geologic mapping schema specifications.

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? PIR 2025-6
  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: 27-Oct-2025
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 Mon Oct 27 14:27:15 2025