Geologic map of the Seldovia quadrangle, south-central Alaska

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Frequently anticipated questions:

What does this data set describe?

Geologic map of the Seldovia quadrangle, south-central Alaska
USGS Open-File Report 99-18B is a digital representation of a paper map that is being released simultaneously, USGS Open-File Report 99-18A. The map shows the bedrock geology of the Seldovia quadrangle, Alaska, at a scale of 1:250,000, compiled from new mapping (1988-1993) and published sources. Digital files include various map coverages in Arc/Info export format, and a picture of the map plus all map-collar information in Adobe Illustrator and PDF formats. The map collar includes detailed map-unit descriptions, text on the physiography, neotectonics, geologic history, and economic geology, cross-section, correlation of map units chart, and map showing original sources of information.
The 1:63,360 scale geologic maps (ink or mylar topographic bases), from which the present map was compiled, are housed at the U.S. Geological Survey, 4200 University Drive, Anchorage, Alaska 99508. These show more detail than the present map, which was simplified, in places, for display at 1:250,000 scale.
  1. How might this data set be cited?
    Bradley, D.C., Kusky, T.M., Haeussler, P.J., Karl, S.M., and Donley, D.T., 1999, Geologic map of the Seldovia quadrangle, south-central Alaska: U.S. Geological Survey Open-File Report OFR 99-18B.

    Online Links:

    Other_Citation_Details: 1 sheet, scale 1:250,000
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -153.0
    East_Bounding_Coordinate: -150.0
    North_Bounding_Coordinate: 60.0
    South_Bounding_Coordinate: 59.0
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 1999
    publication date
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: map
  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
      UTM_Zone_Number: 5
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -153.0
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000
      False_Northing: 0.0
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 50
      Ordinates (y-coordinates) are specified to the nearest 50
      Planar coordinates are specified in meters
  7. How does the data set describe geographic features?
    Characteristics of arcs in svgeol.aat and svfold.aat (Source: USGS OFR-99-0018)
    Arc-code is a positive integer value (3 3 I) item in the arc attribute table. Values range from 1-99. It codes the type of line feature. (Source: USGS OFR-99-0018)
    1Stratigraphic or intrusive contact, location certain
    2Stratigraphic or intrusive contact, location approximate or inferred
    4Normal fault, location certain
    5Normal fault, location approximate or inferred
    7Shoreline or riverbank
    9Boundary of melange zone (invisible line, used to enclose an overprinting pattern)
    11Thrust fault, location approximate, teeth on right from origin
    15Ice contact
    30Fault, sense of displacement unknown, location certain
    32Fault, sense of displacement unknown, location approximate or inferred
    49Dike, Early Cretaceous
    50Dike, Tertiary
    51Stratigraphic or intrusive contact, concealed by younger deposits
    52Fault, sense of displacement unknown, concealed by younger deposits
    53Thrust fault, teeth on right from origin, concealed by younger deposits
    88Right-lateral fault, location approximate or inferred
    91Left-lateral fault, location approximate or inferred
    99Bounding line
    Characteristics of polygon features. Generally these are rock units characterized by a number that is a key into a lookup table (svgeol.lut). (Source: USGS OFR-99-0018)
    Class is a positive integer value (4 5 B) item in the polygon attribute table. Values range from 0-1071. The coverage has a lookup table, svgeol.lut, which contains each class value with a geologic unit label. See the publication for full rock unit descriptions. (Source: USGS OFR-99-0018)
    10Jsm - Seldovia metamorphic complex (Early Jurassic metamorphic age)
    32Jc - Chinita Formation (Upper Jurassic, Callovian)
    47Jn - Naknek Formation (Upper Jurassic, Oxfordian to Kimmeridgian)
    50Jtu - Tuxedni Group (Middle to Upper Jurassic, Bajocian to Callovian)
    60JTrp - Port Graham Formation (Upper Triassic and Lower Jurassic)
    67Jt - Talkeetna Formation (Lower Jurassic; Hettangian to Toarcian)
    71Kv - Valdez Group
    72Kk - Kaguyak Formation (Upper Cretaceous, Maastrichtian)
    74KPmc - McHugh Complex, chert and basalt (Triassic to Cretaceous)
    75KPms - McHugh Complex, graywacke and conglomerate (Jurassic to Cretaceous)
    77KPm - McHugh Complex, undivided (Permian to Cretaceous)
    78Tb - Beluga Formation (Miocene)
    79Twf - West Foreland Formation (Eocene)
    80Ts - Sterline Formation (Miocene to Pliocene)
    81Tt - Tyonek Formation (Oligocene to Miocene)
    82Qs - Surficial deposits (Quaternary)
    105Qv - Iliamna lava flows (Quaternary)
    110Mu - Ultramafic plutonic rocks (Mesozoic)
    111Jd - Diorite of Point Bede (Jurassic)
    112Mg - Gabbro (Mesozoic)
    113Tg - Granodiorite (Eocene)
    115J(?)f - Felsite (Jurassic?)
    116Jto - Tonalite of Dogfish Bay (Jurassic)
    1071Kvm - Melange of Iceworm Peak (Upper Cretaceous) Kd - Intermediate dike (Early Cretceous) (although this is a legitimate map unit, the rock bodies are too narrow to map as polygons, hence are shown as lines with arc-code = 49) Td - Intermediate, felsic, and mafic dikes (Tertiary) (although this is a legitimate map unit, the rock bodies are too narrow to map as polygons, hence are shown as lines with arc-code = 50)

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Bradley, D.C.
    • Kusky, T.M.
    • Haeussler, P.J.
    • Karl, S.M.
    • Donley, D.T.
  2. Who also contributed to the data set?
    Digital representation by Kelly Brunt (Raytheon STX contractor), D. Thomas Donley, and Patti Phillips
  3. To whom should users address questions about the data?
    U.S. Geological Survey
    Attn: Dwight C. Bradley
    4200 University Drive
    Anchorage, AK

    (907)561-1181 (voice)

Why was the data set created?

Digital representation of geologic mapping of the Seldovia quadrangle, Alaska, is to facilitate the presentation and analysis of earth-science data. Digital maps can be displayed at any scale or projection, however the geological data in this coverage is not intended for use at a scale larger that 1:250,000.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 1999 (process 1 of 2)
    Linework was captured by hand digitizing from a stable base line drawing. The digital linework was edited and attributed using ARC/Info. The coverage was built for polygon topology, and had labels created and attributed. For the purpose of distribution, the coverage has been converted to an interchange format file using the ARC/Info export command. The following files are included:
    svgeol.e00     geology (arcs and polygons)
    svfold.e00     fold axial traces
    svisograd.e00  metamorphic isograds
    svquad.e00     outlines of 1:63,360 scale quadrangles
    svsandd.e00    attitudes of bedding and foliation
    svtopo.e00     vectorized contours, not shown over glaciers
    svwells.e00    exploration wells
    Date: 26-May-1999 (process 2 of 2)
    Creation of original metadata record Person who carried out this activity:
    U.S. Geological Survey
    Attn: Nora B. Shew
    4200 University Drive
    Anchorage, AK

    (907)561-1181 (voice)
  3. What similar or related data should the user be aware of?

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

  1. How well have the observations been checked?
    The linework was captured by hand digitizing from 1:63,360 scale mylar maps that were all in excellent condition. The arc and polygon attributes are based on field work and on previously published mapping that is cited, as appropriate, on an inset of the PDF and Illustrator files. Water bodies were digitized from the 1:63,360 scale topographic maps. Glaciers and permanent icefields were digitized from 1:63,360 scale topographic maps, but were modified as needed, based on 1978-1984 vintage air photos, where glacial retreat had been significant. The digital coastline, provided by the State of Alaska, Dept. of Natural Resources, was based on 1:63,360 topographic maps. This digital data set was prepared in the aftermath of the Exxon Valdez oil spill. The source of line- and polygon data is not coded in attribute tables. The map was checked for accuracy by visually comparing the digital product against hand-colored ozalids of the mylars. This thematic bedrock map depicts geologic units present beneath soil or relatively thin mantles of surficial deposits, not necessarily the surficial materials themselves.
  2. How accurate are the geographic locations?
    Users of this digital geologic map should respect the intentions of the original mappers and the limitations of the map. The Seldovia geologic map is intended to be used at a scale of 1:250,000; it is not intended to be used at a more detailed scale.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    This set of digital coverages contains only the information used to create the geologic map. It does not include the files used to create the information shown in collar, or margins, of the paper version and graphic versions of the complete publication.
  5. How consistent are the relationships among the observations, including topology?
    This coverage is a net coverage containing arcs and polygons. Each polygon has a class attribute classifying bedrock, surficial deposit, or water/ice body. Faults and stratigraphic contacts are represented as arcs. When a fault is also a stratigraphic contact, only a single arc is present. Dangling arcs may be present (faults, dikes, etc.)

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None
Acknowledgement of the U.S. Geological Survey would be appreciated in products derived from these data.
  1. Who distributes the data set? (Distributor 1 of 1)
    USGS Information Services
    Box 25286
    Denver Federal Center
    Denver, CO

    303-202-4200 or 1-888-ASK-USGS (voice)
  2. What's the catalog number I need to order this data set? USGS OFR 99-18A - paper version; USGS OFR 99-18B - digital version
  3. What legal disclaimers am I supposed to read?
    Although all this data has been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the acccuracy of the data and related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data, software, or related materials.
  4. How can I download or order the data?

Who wrote the metadata?

Last modified: 05-Feb-2016
Metadata author:
Peter N Schweitzer
USGS Midwest Area
Collection manager, USGS Geoscience Data Clearinghouse,
Mail Stop 954
12201 Sunrise Valley Dr
Reston, VA

703-648-6533 (voice)
703-648-6252 (FAX)
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

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