Rock-eval pyrolysis, vitrinite reflectance, and kerogen microscopy results from Miocene carbonaceous mudstones and coals in outcrop, McGrath Quadrangle, southwestern Alaska

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Frequently anticipated questions:

What does this data set describe?

Title:
Rock-eval pyrolysis, vitrinite reflectance, and kerogen microscopy results from Miocene carbonaceous mudstones and coals in outcrop, McGrath Quadrangle, southwestern Alaska
Abstract:
The Cenozoic Holitna basin is a gravity-defined feature that sits astride the Denali-Farewell fault zone in southwestern Alaska. The basin corresponds to a gravity low in excess of -40 milligals (mGals). No outcrops exist within the footprint of the gravity low and no subsurface data are available; consequently, the stratigraphy and age of its fill are unknown. The Alaska Division of Geological & Geophysical Surveys (DGGS) investigated the shallow gas potential of the basin during the summers of 2000 and 2002 by studying Tertiary coal-bearing rocks exposed along the Denali-Farewell fault zone to the northeast of the basin in the southern McGrath Quadrangle as an outcrop analog to the subsurface stratigraphy of the basin. We visited exposures along Windy Fork Middle Fork River to collect samples for source-rock characterization, including Rock-Eval pyrolysis, vitrinite reflectance measurements, and visual kerogen analysis. Rock-Eval pyrolysis results from carbonaceous mudstone and coal samples along Windy Fork indicate the presence of Type II and Type III kerogen, which are expected to be excellent sources of oil and gas under favorable subsurface conditions. Available thermal maturity data for the samples indicate they are immature for oil and gas, but are in the late pre-oil phase of maturity. If a coal- and carbonaceous-mudstone-bearing succession similar to the rocks discussed in this report from the McGrath Quadrangle are present in the subsurface of the gravity-defined Holitna basin at favorable depths, they can be expected to have significant thermogenic oil and gas generative potential.
Supplemental_Information: 
rock-eval-toc:    Summary of mean vitrinite reflectance, total organic carbon (TOC), and Rock-Eval pyrolysis data
  1. How should this data set be cited?

    LePain, D.L., and Kirkham, Russell, 2015, Rock-eval pyrolysis, vitrinite reflectance, and kerogen microscopy results from Miocene carbonaceous mudstones and coals in outcrop, McGrath Quadrangle, southwestern Alaska: Report of Investigation RI 2015-3, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 60 p., 1 sheet.

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -154.1718
    East_Bounding_Coordinate: -154.13548
    North_Bounding_Coordinate: 62.4190
    South_Bounding_Coordinate: 62.40706

  3. What does it look like?

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

    Beginning_Date: 2002
    Ending_Date: 2015
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: report and digital data

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      This is a point data set.

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

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.0001. Longitudes are given to the nearest 0.00001. Latitude and longitude values are specified in decimal degrees.

      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.

  7. How does the data set describe geographic features?

    ri2015-3-rock-eval-toc.csv
    Summary of mean vitrinite reflectance, total organic carbon (TOC), and Rock-Eval pyrolysis data (Source: Alaska Division of Geological & Geophysical Surveys (DGGS) and Baseline-DGSI)

    LONGITUDE
    Longitude, NAD27 (Source: Alaska Division of Geological & Geophysical Surveys)

    Range of values
    Minimum:-154.1718
    Maximum:-154.13548
    Units:decimal degrees

    LATITUDE
    Latitude, NAD27 (Source: Alaska Division of Geological & Geophysical Surveys)

    Range of values
    Minimum:62.40706
    Maximum:62.419
    Units:decimal degrees

    SAMPLE
    Label assigned in the field to identify the sample. (Source: Alaska Division of Geological & Geophysical Surveys)

    Generic example of a sample identifier: YYAA9999X or YYAA99-99; YY=last two digits of year, AA=geologist's initials (one to three characters), 9999=unique station number, X= optional alpha character which indicates that multiple samples were collected at a given location, -99= distance in meters from base of measured section.

    FIELD_LITHOLOGY
    Lithology assigned to the sample when it was collected in the field (Source: Alaska Division of Geological & Geophysical Surveys)

    Possible values: carbonaceous claystone, carbonaceous claystone and siltstone, carbonaceous claystone or high-ash coal, coal, coal with carbonaceous claystone partings, coal with interbedded carbonaceous claystone splits, heterolithic - clayey siltstone and carbonaceous claystone, heterolithic - siltstone and carbonaceous claystone, heterolithic - siltstone, carbonaceous claystone, and coal, heterolithic - siltstone, carbonaceous claystone, coal, heterolithic - siltstone, carbonaceous claystone, coal stringers, no field assigned lithology, nodular siltstone, siltstone, siltstone and carbonaceous claystone, or siltstone with coal stringers;

    TOC_BASED_LITHOLOGY
    Revised lithology assignment, modifications incorporate the total organic carbon (TOC) values (Source: Alaska Division of Geological & Geophysical Surveys)

    Possible values: carbonaceous claystone, coal, carbonaceous siltstone, carbonaceous siltstone/claystone, carbonaceous mudstone, or mudstone

    MEAN_VR
    Mean vitrinite reflectance (Source: Baseline-DGSI)

    ValueDefinition
    NULLNULL or blanks indicate that the measurement was not applicable

    Range of values
    Minimum:0.42
    Maximum:0.59
    Units:%Ro

    TOC_WT_PCT
    Total organic carbon (TOC) (Source: Baseline-DGSI)

    Range of values
    Minimum:1.11
    Maximum:74.35
    Units:weight%

    S1
    Amount of hydrocarbons volatilized from the sample by heating to 300 degrees C and represents the hydrocarbons in the sample at the start of the procedure (Source: Baseline-DGSI)

    Range of values
    Minimum:0.03
    Maximum:3.05
    Units:mg/g

    S2
    Measure of the hydrocarbons generated by pyrolytic degradation of kerogen (cracking) by heating from 300 degrees C to 550 degrees C in 25 degrees C per minute increments. S2 represents the generative potential remaining in the sample. (Source: Baseline-DGSI)

    Range of values
    Minimum:0.49
    Maximum:156.89
    Units:mg/g

    S3
    Measure of the carbon dioxide generated during S2 heating up to 390 degrees C (Source: Baseline-DGSI)

    Range of values
    Minimum:0.51
    Maximum:12.81
    Units:mg CO2/g rock

    TMAX
    Temperature of maximum S2 generation (Source: Baseline-DGSI)

    Range of values
    Minimum:406
    Maximum:439
    Units:degrees C

    HI
    Hydrogen index (HI = S2/TOC) (Source: Baseline-DGSI)

    Range of values
    Minimum:44
    Maximum:312

    OI
    Oxygen index (OI = S3/TOC) (Source: Baseline-DGSI)

    Range of values
    Minimum:7
    Maximum:82

    S1_TOC
    Ratio (S1/TOC)x100 (Source: Baseline-DGSI)

    Range of values
    Minimum:2
    Maximum:9

    PI
    Production index (Source: Baseline-DGSI)

    Range of values
    Minimum:0.01
    Maximum:0.11

    S2_S3
    Ratio (S2/S3) (Source: Baseline-DGSI)

    Range of values
    Minimum:0.5
    Maximum:36.3

    NOTES
    a brief sample or station description (Source: Alaska Division of Geological & Geophysical Surveys)

    ValueDefinition
    NULLWe do not provide notes or additional descriptive information about the sample or station.

    Characters 1 to 254 of a brief sample or station description.

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?

    The work summarized in this report was funded by the State of Alaska. We gratefully acknowledge Calista Corporation for their support of this work. We thank Rick Stanley for discussions regarding the petroleum source potential of coal and for reviewing a draft of this manuscript.

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

    Alaska Division of Geological & Geophysical Surveys
    GIS Manager
    3354 College Road
    Fairbanks, AK 99709-3707
    USA

    (907)451-5020 (voice)
    dggsgis@alaska.gov

    Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays

Why was the data set created?

This dataset provides source-rock characterization results (Rock-Eval pyrolysis, vitrinite reflectance measurements, and visual kerogen analysis) from outcrop exposures along Windy Fork Middle Fork River.

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: 2002 (process 1 of 2)
    Fieldwork - We measured a stratigraphic section along the north end of the Windy Fork River exposure and collected an extensive suite of samples suitable for Rock-Eval pyrolysis from mudstones, carbonaceous mudstones, and coals (fig. 3, on sheet). Grab samples for Rock-Eval were also collected south of locality 02DL53, a short distance north of the mapped trace of the Farewell fault, at locality 02DL54. More information can be found in the accompanying report.

    Date: 2002 (process 2 of 2)
    Analysis - Samples were analyzed by Baseline-DGSI for mean vitrinite reflectance, total organic carbon (TOC), and Rock-Eval pyrolysis.

  3. What similar or related data should the user be aware of?

    Burns, L.E., SIAL Geosciences, Inc., and On-line Exploration Services, Inc., 2008, Linedata and gridded data for the aeromagnetic survey of the Holitna basin area, western Alaska: Parts of the Lime Hills and Sleetmute quadrangles: Geophysical Report GPR 2008-4, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 DVD
    Staff, DGGS, On-line Exploration Services, Inc., and SIAL Geosciences, Inc., 1998, Total field magnetics and flight line paths of the Holitna Basin area, western Alaska: Public Data File PDF 98-27, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 4 sheets, scale 1:125,000
    Staff, DGGS, On-line Exploration Services, Inc., and SIAL Geosciences, Inc., 1998, Total field magnetics of the Holitna Basin area, western Alaska: Report of Investigation RI 98-14, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 2 sheets, scale 1:125,000
    Edcon, Inc., 2001, Edcon land gravity survey, Holitna Basin, southwest Alaska: Geophysical Report GPR 2001-1, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 DVD
    LePain, D.L., Blodgett, R.B., Clough, J.G., Ryherd, T.J., and Smith, T.N., 2000, Generalized stratigraphy and petroleum potential of the Holitna region, southwest Alaska: Preliminary Interpretive Report PIR 2000-1, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 34 p., 1 sheet, scale 1:250,000
    LePain, D.L., Blodgett, R.B., and Clough, J.G., 2003, Sedimentology and hydrocarbon source rock potential of Miocene-Oligocene strata, McGrath Quadrangle: An outcrop analog for the Holitna Basin: Preliminary Interpretive Report PIR 2002-5, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 75 p
    SIAL Geosciences, Inc., and On-line Exploration Services, Inc., 1998, Project report of the aeromagnetic survey for the Holitna Basin area, western Alaska: Public Data File PDF 98-29, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 82 p., 2 sheets, scale 1:125,000
    Tyler, Roger, Scott, A.R., and Clough, J.G., 2000, Coalbed methane potential and exploration targets for rural Alaska communities: Preliminary Interpretive Report PIR 2000-2, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 169 p
    Zippi, P.A., 2001, Palynology of Tertiary Holitna outcrops, McGrath and Talkeetna quadrangles: Preliminary Interpretive Report PIR 2001-4, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 22 p

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

  1. How well have the observations been checked?

    This DGGS Report of Investigations is a final report of scientific research. It has received technical review by several scientists familiar with the subject matter. Uncertainties associated with the depiction or interpretation of various analytical values are discussed in the accompanying manuscript.

  2. How accurate are the geographic locations?

    Samples 02DL054A-F were grab samples collected within a 5 meter radius of the reported location coordinates. Samples with the 02DL53 prefix were collected along a measured section. Location coordinates are provided for the base of the section. The numeric suffix of each of the sample numbers indicates the the distance, in meters, from the base of the section.

  3. How accurate are the heights or depths?

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

    This DGGS Report of Investigations is a final report of scientific research.

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

    not applicable

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
    3354 College Road
    Fairbanks, AK 99709-3707
    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 (<http://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 2015-3

  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: 28-Apr-2015
Metadata author:
Alaska Division of Geological & Geophysical Surveys
Metadata Manager
3354 College Road
Fairbanks, AK 99709-3707
USA

(907)451-5020 (voice)

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

Generated by mp version 2.9.21 on Tue Apr 28 15:51:20 2015