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Generalized thermal maturity map of Alaska

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Frequently-anticipated questions:

What does this data set describe?

Title: Generalized thermal maturity map of Alaska
Abstract:
This dataset consists of a polygon coverage and associated attribute data derived from the onshore portion of the 1996 "Generalized Thermal Maturity Map of Alaska" compiled by M.J. Johnsson and D.G. Howell, which was published as Plate 1 in US Geological Survey Bulletin 2142: "Thermal Evolution of Sedimentary Basins in Alaska". The published map summarizes vitrinite reflectance and conodont alteration index data (both measure the thermal maturity of rocks) into generalized units that can be shown cartographically at 1:2,500,000. This digital dataset includes the 8 map units indicated on the original map. (5 thermal maturity levels; 2 rock or sediment type; 1 "no data"). The data quality of the generalized information is retained, with an attribute value for "certainty" whose value choices are "questioned" or "certain". Additional data retained in a look-up table are the maximum and minimum vitrinite reflectance and conodont alteration index values assigned to each thermal maturity level. This coverage is not intended to be a complete representation of the printed map. It does NOT include the following features: locations of individual vitrinite or conodont sample data points (these data are available in: Johnsson and others, 1992, USGS Open File Report 409, 3 diskettes); faults; offshore maturity data (from dredge and well samples); cities, glaciers, wells; inset maps and subsurface contours for the Colville basin and Cook Inlet; the correlation chart, text or references printed on the map.
  1. How should this data set be cited?

    U.S. Geological Survey, 1997, Generalized thermal maturity map of Alaska: U.S. Geological Survey, Anchorage, AK.

    Online Links:

    This is part of the following larger work.

    Johnsson, M.J. (ed.), and Howell, D.G. (ed.), 1996, Thermal evolution of sedimentary basins in Alaska: U.S. Geological Survey Bulletin B-2142.

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -176.0
    East_Bounding_Coordinate: -130.0
    North_Bounding_Coordinate: 72.0
    South_Bounding_Coordinate: 51.0

  3. What does it look like?

    <http://agdc.usgs.gov/data/usgs/geology/images/maturity.gif> (GIF)
    Reduced-size image of the entire map extent, 712x563 pixels, 18k bytes.

  4. Does the data set describe conditions during a particular time period?

    Calendar_Date: 1997
    Currentness_Reference: Publication date = 1996

  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. It contains the following vector data types (SDTS terminology):

      • Point (1575)
      • String (3453)
      • GT-polygon composed of chains (1576)

    2. What coordinate system is used to represent geographic features?

      The map projection used is Albers Conical Equal Area.

      Projection parameters:
      Standard_Parallel: 55
      Standard_Parallel: 65
      Longitude_of_Central_Meridian: -154
      Latitude_of_Projection_Origin: 50
      False_Easting: 0.00000
      False_Northing: 0.00000

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 1.0
      Ordinates (y-coordinates) are specified to the nearest 1.0
      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 1/294.98.

  7. How does the data set describe geographic features?

    MATURITY.PAT
    Attribute table of Maturity

    MATURITY
    Thermal-maturity units (Source: Generalized Thermal Maturity Map of Alaska, 1996.)

    ValueDefinition
    UUndermature
    M1Mature I
    M2Mature II
    OOvermature
    SSupermature
    Ig-MIgneous-Metamorphic
    QsQuaternary sediments (unconsolidated)
    NDNo data

    CERTAINTY
    Confidence of thermal-maturity unit (Source: Generalized Thermal Maturity Map of Alaska, 1996.)

    ValueDefinition
    CCertain
    QQuestioned

    MATURITY.DAT
    Explanation of thermal-maturity units in terms of vitrinite reflectance and conodont alteration index values used to define them. (Source: U.S. Geological Survey Bulletin 2142)

    MATURITY
    Thermal-maturity units (Source: Generalized Thermal Maturity Map of Alaska, 1996.)

    ValueDefinition
    UUndermature
    M1Mature I
    M2Mature II
    OOvermature
    SSupermature
    Ig-MIgneous-Metamorphic
    QsQuaternary sediments (unconsolidated)
    NDNo data

    RO-MIN
    Minimum vitrinite reflectance value occurring in a thermal maturity unit. (Source: U.S. Geological Survey Bulletin 2142)

    Range of values
    Minimum:0
    Maximum:5.01
    Resolution:0.01

    RO-MAX
    Maximum vitrinite reflectance value occurring in a thermal maturity unit. (Source: U.S. Geological Survey Bulletin 2142)

    Range of values
    Minimum:0.01
    Maximum:8
    Resolution:0.01

    CAI-MIN
    Minimum conodont alteration index value occurring in a thermal maturity unit. (Source: U.S. Geological Survey Bulletin 2142)

    Range of values
    Minimum:0
    Maximum:5
    Resolution:0.01

    CAI-MAX
    Maximum conodont alteration index value occurring in a thermal maturity unit. (Source: U.S. Geological Survey Bulletin 2142)

    Range of values
    Minimum:0.1
    Maximum:8
    Resolution:0.01

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?

    D. C. Pray, J. M. Schmidt

  3. To whom should users address questions about the data?

    U.S. Geological Survey Alaska Section, Mineral Resource Surveys Program, Geologic Division
    GIS Support Staff
    4200 University Dr.
    Anchorage, AK 99508-4667

    (907)-786-7495 (voice)

Why was the data set created?

This coverage is intended to provide digital features (polygons) representing generalized thermal maturity units in Alaska for use in small-scale spatial analysis (statewide) with similar coverages such as geologic units,vegetation types, soils, etc. Johnsson, M.J., Pawlewica, M.J., Harris, A.G., and Valin, Z.C., 1992, Vitrinite reflectance and conodont color alteration index data from Alaska: Data to accompany the Thermal Maturity Map of Alaska: U.S. Geological Survey Open File Report 92-409, 3 Macintosh-formatted 3 1/2" high density (1.44 Mb) diskettes.

How was the data set created?

  1. From what previous works were the data drawn?

    (source 1 of 2)
    U.S. Geological Survey, 1996, Generalized Thermal Maturity Map of Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map I-2494, U.S. Government Printing Office, Washington, D.C..

    Type_of_Source_Media: Paper map
    Source_Scale_Denominator: 2500000

    (source 2 of 2)
    Johnsson, M.J., Pawlewica, M.J., Harris, A.G., and Valin, Z.C., 1992, Vitrinite reflectance and conodont color alteration index data from Alaska: Data to accompany the Thermal Maturity Map of Alaska: U.S. Geological Survey Open File Report 92-409.

    Type_of_Source_Media: floppy disk
    Source_Scale_Denominator: 2500000

  2. How were the data generated, processed, and modified?

    Date: 1997 (process 1 of 1)
    The linework was digitized in 1997 from a paper copy of the 1996 map at the U.S. Geological Survey's Alaska Section (Geologic Division) facilities in Anchorge, AK. The original Transverse Mercator projection of the map (Central Meridian: 100*W; Scale factor: 0.926; Reference ellipsoid:(6371204m, 63712004m)) was converted to an Albersequal-area coverage in ARC/INFO (version 7.1.2). The resulting coverage did not align exactly with an Albers equal-area coverage of the Alaskan coastline, so a rubber-sheeting operation was performed using points along the coastline and major rivers to match an Albers equal area projection. Map unit (polygon) locations and attributes were checked by the person responsible for the digitizing, and spot-checked by one reviewer reviewer, by comparing a printed copy of the coverage to the published map.

  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 completeness and quality of the generalized maturity data in the digital coverage is that of the published 1996 map, which itself summarized data released in 1992 and collected prior to that date (mainly since 1980). No recent data have been added. The geographic accuracy of the published map has been slightly degraded by the rubber-sheet operation.

  2. How accurate are the geographic locations?

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    The following map features are not included in the digital representation: Offshore data, faults, glaciers,subsurface contours, cities, wells, inset maps, correlation chart, text and references.

  5. How consistent are the relationships among the observations, including topology?

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: none
Use_Constraints:
This coverage should not be copied or distributed without its associated metadata file. Intended use is at small scales (e.g. statewide, 1:2,500,000 etc.) only; enlargements of this data to scales greater than that at which they were originally compiled can lead to misinterpretation of data. The U.S. Geological Survey (Dept. of Interior) should be acknowledged as the data source in products derived from these data. Use of these data is not restricted; however, organizations, agencies, units of government or other users are responsible for its appropriate application.

  1. Who distributes the data set? (Distributor 1 of 1)

    Alaska Geographic Data Committee
    4230 University Drive
    Anchorage, AK 99508-4664

    agdcweb@usgs.gov

  2. What's the catalog number I need to order this data set?

  3. What legal disclaimers am I supposed to read?

    Although these data have been processed successfully on a computer system at the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the Geological Survey regarding the utility of the data on any other system, nor shall the act of distribution constitute any such warranty. The U.S. Dept. of Interior, nor any of its agencies are liable for misuse of the data, nor for any damage, transmission of viruses or computer contamination caused through transmission of these data sets.

  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 14-Feb-2003
Metadata author:
Peter N Schweitzer
U.S. Geological Survey, ER
Geologist
Mail Stop 954
12201 Sunrise Valley Drive
Reston, VA 20192
USA

703-648-6533 (voice)
703-648-6252 (FAX)
pschweitzer@usgs.gov

Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <http://tin.er.usgs.gov/metadata/maturity.faq.html>

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URL: http://tin.er.usgs.gov/metadata/maturity.faq.html
Page Contact Information: Peter Schweitzer
Page Last Modified: Thursday, 18-Oct-2007 13:17:58 EDT

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