Geology and geologic hazards of offshore Eel River basin, northern California continental margin

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Frequently-anticipated questions:

What does this data set describe?

Title:
Geology and geologic hazards of offshore Eel River basin, northern California continental margin
Abstract:
No formal abstract is given. The prefaces states, " This report summarizes aspects of the offshore and onshore geology of the Eel River Basin, California, that are of importance in assessing the potential geological hazards to offshore petroleum exploration and development. Although these investigations focus on the identification and characterization of potential hazards in specific offshore basins, they should be considered regional in scope. They are designed to provide broad geological perspective in these areas, to be used as an adjunct to site-specific geohazards studies. The geologic phenomena investigated include faulting, seismicity, seafloor instability (e.g., submarine slides and flows), seafloor erosion and deposition, hydrocarbon seepage, hydrocarbon gases and hydrates in seafloor sediments, and diapirism."
Supplemental_Information:
"This research was supported by the Pacific OCS Office of the Bureau of Land Management in Los Angeles and we are appreciative of their support." Data digitized by the USGS for inclusion into usSEABED (<http://walrus.wr.usgs.gov/usseabed>)
  1. How should this data set be cited?

    Field, Michael E. , Samuel H. Clarke, Jr., and White, Michael E. , 1980, Geology and geologic hazards of offshore Eel River basin, northern California continental margin: Open-file report 80-1080, U.S. Geological Survey, Menlo Park, CA.

    Online Links:

    • <http://onlinepubs.er.usgs.gov/djvu/OFR/1980/ofr_80_1080.djvu>

    Other_Citation_Details:
    Data from USGS cruise S977NC (<http://walrus.wr.usgs.gov/infobank/s/s977nc/html/s-9-77-nc.meta.html>).

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -125.0117
    East_Bounding_Coordinate: -124.2175
    North_Bounding_Coordinate: 41.6921
    South_Bounding_Coordinate: 40.6870

  3. What does it look like?

    OFR_80_1080 (JPG)
    Screen grab of GIS-produced sample distribution, with bathymetry and land for reference.

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

    Beginning_Date: 11-Nov-1977
    Ending_Date: 16-Nov-1977
    Currentness_Reference: Publication date

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

    Geospatial_Data_Presentation_Form: Paper

  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 (105)

    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 0.0001. Latitude and longitude values are specified in Decimal degrees.

  7. How does the data set describe geographic features?

    Point
    SDTS point (Source: Source report)

    Sample number
    Sample number (Source: US Geological Survey)

    Alpha numeric number based on cruise and core information

    Water depth
    Depth of water at sample site (Source: Source report)

    Range of values
    Minimum:55
    Maximum:2467
    Units:Meters
    Resolution:1.0

    Gravel
    Gravel (Source: Wentworth, 1932)

    Range of values
    Minimum:0
    Maximum:53.0
    Units:Percent
    Resolution:0.1

    Sand
    Sand (Source: Wentworth 1932)

    Range of values
    Minimum:0
    Maximum:87.0
    Units:Percent
    Resolution:0.1

    Mud
    Mud (Source: Wentworth 1932)

    Range of values
    Minimum:13
    Maximum:100
    Units:Percent
    Resolution:0.1

    Median
    Median grainsize (Source: Wentworth 1932)

    Range of values
    Minimum:-1.01
    Maximum:7.42
    Units:Phi
    Resolution:0.01

    Mean
    Mean grainsize (Source: Inman, 1952)

    Range of values
    Minimum:0.95
    Maximum:8.22
    Units:Phi
    Resolution:0.01

    Sorting
    Standard deviation about the grain size mean (Source: Inman, 1952)

    Range of values
    Minimum:0.35
    Maximum:4.11
    Units:Phi
    Resolution:0.01

    Skewness
    Skewness of grain size distribution (Source: Inman, 1952)

    Range of values
    Minimum:-0.2
    Maximum:0.92
    Units:Unitless
    Resolution:0.01

    Kurtosis
    Kurtosis of grain size distribution (Source: Inman, 1952)

    Range of values
    Minimum:0.45
    Maximum:4.95
    Units:Unitless
    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?

    Michael E. Field, Samuel H. Clarke, Jr. and Michael E. White at the USGS for collection and analysis of data. For usSEABED, digitization and formatting: Jennifer Mendonca (USGS); Formatting corrections: Jane Reid (USGS) and Chris Jenkins (University of Colorado)

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

    United States Geological Survey
    USGS Information Services
    Denver, CO 80225

    1-800-ASK-USGS (voice)

Why was the data set created?

"[To assess] the potential geological hazards to offshore petroleum exploration and development."

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: Unknown (process 1 of 1)
    " Subsamples from the surface of 63 gravity cores were analyzed for grain size distribution. About 5 grams of each sample were placed in individual 1000 ml beakers and diluted with about 100 ml of 10% hydrogen peroxide to remove particulate organic material. Remaining sediment was wet sieved through a 0.063 mm sieve to separate the sand and mud fractions. The sand fraction (>0.063 mm) was oven-dried and split into 0.5 gram fractions for size analysis with a rapid sediment analyzer (RSA) settling tube. Duplicates were run for every tenth machine run. Mud fractions (<0.063 mm) were diluted to 1000 ml, dispersed with sodium hexametaphosphate, and a 10 to 25 ml split was taken for grain size analysis using light transmission techniques on a hydrophotometer (Jordan and others, 1971; Tilly, 1977). Replicate analyses show high reproducibility using this technique. Particle size distribution and modal, median and mean size, sorting, skewness and kurtosis were calculated using both the methods of moments and graphical statistics. Duplicate analyses show no major discrepancies." [No data for carbon is given in the report]: "Subsamples from these same 63 cores were analyzed for total, inorganic (carbonate) and organic carbon. Approximately 1-2 grams of sediment from each subsample was washed twice with distilled water by centrifuging and decanting to remove fluoride and chloride salts that might affect the results of carbon analysis. Washed sediment was oven-dried, ground to fine powder with mortar and pestle, and stored in airtight glass vials at room temperature. Total carbon content was determined by combustion of 0.02 gram samples for 55 seconds in a LECO tube-induction furnace. Evolved carbon dioxide gas was measured in a LECO model WR 12 carbon determinator modified after Kolpack and Bell (1968). Inorganic carbon was determined gasometrically by measuring the amount of carbon dioxide generated from sediment (0.1 gm) treated with 2 N HCI (Kolpack and Bell, 1968). Carbon content was determined by averaging three analytical runs for each between total carbon and inorganic carbon. Calcium carbonate content was derived from the analyses by multiplying the amount of inorganic carbon by the ratio of molecular weight of CaCO3 (= 100) to the atomic weight of carbon (12). Thus, a value of 0.25% inorganic carbon equates to a value of 0.25 x 100/12 or 2.08% calcium carbonate." For usSEABED, these data were concatenated with petrographic analyses on the same samples. Petrographic data from OFR 95-614 by F. Wong. Metadata for that report is given separately.

    Person who carried out this activity:

    U.S. Geological Survey
    c/o Michael E. Field
    USGS Pacific Science Center
    Santa Cruz, CA 95060

    831-427-4737 (voice)
    mfield@usgs.gov

    Data sources used in this process:
    • Jordan and others, 1971
    • Kolpack and Bell, 1968
    • Tilly, 1977

    Data sources produced in this process:

    • OFR_80_1080

  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?

    No estimate made for original data, although the report text notes that replicate analyses show high reproducibility. For usSEABED, data were digitized, visually compared to the source and corrected. Where appropriate, data were tested for completeness using MS Excel.

  2. How accurate are the geographic locations?

    Positioning data were obtained at sea using satellite navigation and Loran C systems, and a shipborne electronic ranging system employing shore- based transponders. Radar was used infrequently for positioning where terrain masking or equipment malfunctions were encountered. Data from the satellite and Loran C systems were integrated by means of a Dead Reckoning computer (DRC). Positions derived from the DRC and electronic ranging systems initially were plotted separately and weighted according to their relative accuracy; subsequently these data were corrected and merged to produce maps of position location for geophysical tracklines and sampling stations. Estimated position accuracy ranges from + 50 m where positions were determined principally by electronic ranging (approximately 90 percent of the cruise) to an average of about + 500 m where DRC or radar positions were used exclusively (approximately 10 percent of the cruise). Positions given to 0.0001 decimal degrees.

  3. How accurate are the heights or depths?

    Precision bathymetric and shallow subbottom records were obtained using 12 kHz and 3.5 kHz profiling systems employing hull-mounted transducers and hydrophones. Subsample depths given as nearest centimeter.

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

    No estimate made for original data. For inclusion into usSEABED, all data in the report were included.

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

    Data fall within normal ranges for the given parameters.

How can someone get a copy of the data set?

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

Access_Constraints:
None. Paper copy of report is available through the USGS, and is also available online.
Use_Constraints:
Cite Michael Field, Sam Clarke,and Michael White and the U.S. Geological Survey as the originators of the data.

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

    United States Geological Survey
    USGS Information Services
    Denver, CO 80225

    1-800-ASK-USGS (voice)

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

    Open file report 80-1080

  3. What legal disclaimers am I supposed to read?

    Although this dataset has been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data. Users of the data should be aware of limitations of the data due to possible imprecision due to navigational inaccuracies and limitations of the statistical data.

  4. How can I download or order the data?

  5. What hardware or software do I need in order to use the data set?

    Plug-in not required, but best viewed with downloadable program DjVu at <http://www.lizardtech.com/download/dl_options.php?page=plugins>

Who wrote the metadata?

Dates:
Last modified: 2005
Metadata author:
U.S. Geological Survey
c/o Jane A. Reid
Geologist
400 Natural Bridges Drive
Santa Cruz, CA 95060

831-427-4727 (voice)
jareid@usgs.gov

Contact_Instructions: Email preferred
Metadata standard:
CSDGM Version 2 (FGDC-STD-001-1998)

Generated by mp version 2.8.17 on Sun May 21 08:09:53 2006