Core locations, segment depths, and estimated compaction from vibracores collected in Searsville Lake, Jasper Ridge Biological Preserve, Stanford, California

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Frequently anticipated questions:

What does this data set describe?

Title:
Core locations, segment depths, and estimated compaction from vibracores collected in Searsville Lake, Jasper Ridge Biological Preserve, Stanford, California
Abstract:
This portion of the data release presents measurements and data from two vibracores (JRBP2018-VC01A and JRBP2018-VC01B) collected from Searsville Lake, a reservoir in the Jasper Ridge Biological Preserve, Stanford, California, on October 29, 2018 (USGS Field Activity 2018-682-FA). Vibracoring introduced significant amounts of sediment compaction. The core depths in other datasets of this data release are not corrected for compaction. Translated depths are provided in this portion of the data release that return the tops of each core to the lakebed surface (0 cm).
Supplemental_Information:
Additional information about the field activities from which these data were derived is available online at:
https://cmgds.marine.usgs.gov/fan_info.php?fan=2018-682-FA
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  1. How might this data set be cited?
    SeanPaul M. La Selle, Stegner, M. Allison, Nasr, Brandon M., Hadly, Elizabeth A., Barnosky, Anthony D., and Sherrod, Brian, 20230131, Core locations, segment depths, and estimated compaction from vibracores collected in Searsville Lake, Jasper Ridge Biological Preserve, Stanford, California: data release DOI:10.5066/P98CEB1B, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    This is part of the following larger work.

    SeanPaul M. La Selle, Stegner, M. Allison, Nasr, Brandon M., Hadly, Elizabeth A., Barnosky, Anthony D., and Sherrod, Brian, 2023, Computed Tomography (CT) scans, photographs, X-ray Fluorescence (XRF) scans, grain size, and gamma-ray bulk density data of vibracores from Searsville Lake, Jasper Ridge Biological Preserve, Stanford, California: data release DOI:10.5066/P98CEB1B, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -122.23787
    East_Bounding_Coordinate: -122.23783
    North_Bounding_Coordinate: 37.40684
    South_Bounding_Coordinate: 37.40683
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 29-Oct-2018
    Ending_Date: 29-Oct-2018
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: comma-delimited text
  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. It contains the following vector data types (SDTS terminology):
      • Point (13)
    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 0.00004. Longitudes are given to the nearest 0.00001. Latitude and longitude values are specified in Decimal Degrees. The horizontal datum used is WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.25722356.
  7. How does the data set describe geographic features?
    searsville_core_data.csv
    Comma Separated Value (CSV) file containing data. The first row is a header row. (Source: Producer Defined)
    field_activity_number
    Field Activity Number (Source: Producer Defined) Unique field activity number for U.S. Geological Survey field activity 2018-682-FA.
    date collected
    The date of core collection in mm/dd/yy format. (Source: Producer Defined) Both cores were collected on the 29th of October, 2018.
    core_id
    Unique name for each core (Source: Producer Defined) Unique name for the core in LocalityYear-CoreID format, where LocalityYear is a four-letter abbreviation of the field locality (for example JRBP = Jasper Ridge Biological Preserve) followed by the 4-digit year (2018), and CoreID is the unique name given to a core (for example VC01B is Vibracore 01 B).
    segment_number
    Cores were split into approximately 150 cm or shorter segments or sections to fit in scanning equipment. The segment number denotes the section of core starting from the top of the original, unsectioned core. (Source: Producer Defined)
    Range of values
    Minimum:1
    Maximum:7
    longitude
    The longitude in decimal degrees where the core was collected. (Source: Producer Defined)
    Range of values
    Minimum:-122.23787
    Maximum:-122.23783
    Units:decimal degrees
    latitude
    The longitude in decimal degrees where the core was collected. (Source: Producer Defined)
    Range of values
    Minimum:37.40683
    Maximum:37.40684
    Units:decimal degrees
    water_depth_cm
    The water depth in centimeters above the lakebed at the core collection site (Source: Producer Defined)
    Range of values
    Minimum:265
    Maximum:268
    Units:centimeters
    segment_upper_depth_cm
    The depth below the lakebed in centimeters of the top of a core segment. (Source: Producer Defined)
    Range of values
    Minimum:158.5
    Maximum:990.0
    Units:centimeters
    segment_upper_depth_lakebed_cm
    The depth below the lakebed in centimeters of the top of a core segment, ignoring sediment compaction and translating all core depths so the top of the uppermost core segment is at 0 centimeters. (Source: Producer Defined)
    Range of values
    Minimum:0
    Maximum:738
    Units:centimeters
    segment_length_cm
    The length of the core segment in centimeters. (Source: Producer Defined)
    Range of values
    Minimum:55.5
    Maximum:151
    Units:centimeters
    core_compaction_pct
    The amount of sediment compaction introduced during coring, expressed as the percentage represented by the length of sediment within the core divided by the total depth driven below the lakebed surface by the core string. (Source: Producer Defined)
    Range of values
    Minimum:15
    Maximum:24
    Units:percentage

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • SeanPaul M. La Selle
    • M. Allison Stegner
    • Brandon M. Nasr
    • Elizabeth A. Hadly
    • Anthony D. Barnosky
    • Brian Sherrod
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    PCMSC Science Data Coordinator
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    2885 Mission Street
    Santa Cruz, CA

    831-427-474 (voice)
    pcmsc_data@usgs.gov

Why was the data set created?

Data presented in this portion of the data release provide core locations and depths. These data are intended for science researchers, students, policy makers, and the general public.

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: 29-Oct-2018 (process 1 of 2)
    Cores were collected from the USGS coring platform Hadai. Water depth was measured using a reel tape measure with a weighted disc to determine the sediment surface. A handheld global satellite navigation system (GNSS) receiver was used to determine the locations of sediment samples. Lake sediment was collected in approximately 6-meter-long aluminum irrigation pipes with an outer diameter of 76.2 mm and a wall width of 1.27 mm. Pipes were coupled using aluminum sleeves, and a Honda GX160 5-horsepower 4-stroke motor drove a concrete vibrator head at approximately 167 Hz, which was clamped to the pipes. Brass-fingered core-catchers were used to prevent loss of sediment out the bottom of the pipes during extraction. Cores were segmented into 150 cm or shorter lengths. The top and bottom depths of each core segment are reported in centimeters below the lakebed. Due to significant sediment compaction while coring, the sediments originally at the lakebed surface (0 cm) were driven down to 289 cm in VC01A and 158.5 cm in VC01B. The upper sediment layers in these cores are compacted more than the sediment layers near the bottom, around 11 meters below the lakebed, thus the grains of sediment near the bottom of the core are closer to their true depths before being disturbed by coring. The core depths in the other datasets of this data release report uncorrected depths, thus the uppermost core segments start at 158.5 and 289 cm, even though the sediment at the top of these core segments represent the lakebed surface (0 cm) on October 29, 2018. Associated publications may use depths that are corrected to 0 cm at the top. The comma-separated values (csv) file in this dataset provides both the original and the corrected upper depths for each segment. Compaction percentages were calculated in the field after driving the vibracores to refusal, but before extraction, by dividing the distance from the lakebed surface to the top of the sediment in the pipe within the core by the total drive (distance below the lakebed that the core string was driven). The compaction was 15 percent and 24 percent for VC01A and VC01B, respectively. Core depths and water depths were not associated with a fixed vertical datum at the time of core collection. Cores were segmented into 150 cm (or shorter) sections in the field and split into "working" and "archive" halves in the lab. Person who carried out this activity:
    SeanPaul La Selle
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Geologist
    2885 Mission St.
    Santa Cruz, CA

    831-460-7574 (voice)
    slaselle@usgs.gov
    Date: 23-Feb-2023 (process 2 of 2)
    corrected typo in doi number (scochran@usgs.gov)
  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 formal attribute accuracy tests were conducted
  2. How accurate are the geographic locations?
    The locations of samples were determined using a Garmin etrex 30x handheld global satellite navigation system (GNSS) receiver capable of receiving wide area augmentation system (WAAS) signals. The manufacturer reported accuracy for horizontal positions is 3-5 m while receiving WAAS signals.
  3. How accurate are the heights or depths?
    Core location depths and water depths were not associated with a fixed vertical datum at the time of core collection. No formal positional accuracy tests were conducted.
  4. Where are the gaps in the data? What is missing?
    Dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details.
  5. How consistent are the relationships among the observations, including topology?
    No formal logical accuracy tests were conducted

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints None. Please see 'Distribution Info' for details.
Use_Constraints None. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations.
  1. Who distributes the data set? (Distributor 1 of 1)
    GS ScienceBase
    U.S. Geological Survey
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO
    United States

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? Core information data are available in comma-delimited text file format (JRBP2018-coredata), including FGDC-compliant metadata.
  3. What legal disclaimers am I supposed to read?
    Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 23-Feb-2023
Metadata author:
PCMSC Science Data Coordinator
U.S. Geological Survey, Pacific Coastal and Marine Science Center
2885 Mission Street
Santa Cruz, CA

831-427-4747 (voice)
pcmsc_data@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/pcmsc/DataReleases/ScienceBase/DR_P98CEB1B/JRBP2018-coredata-metadata.faq.html>
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