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Florida Bay sample core log

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Frequently-anticipated questions:

What does this data set describe?

Title: Florida Bay sample core log
Abstract:
The data set contains fractions, intervals, location of sample, analyses, and sections with no sample remaining referenced to site name.
  1. How should this data set be cited?

    Charles W. Holmes (retired) Debra Willard, Unknown, Florida Bay sample core log.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -81.096
    East_Bounding_Coordinate: -80.4082
    North_Bounding_Coordinate: 25.2091
    South_Bounding_Coordinate: 24.9843

  3. What does it look like?

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

    Beginning_Date: 07-Feb-1994
    Ending_Date: 13-Jun-1997
    Currentness_Reference: ground condition

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

    Geospatial_Data_Presentation_Form: spreadsheets

  6. How does the data set represent geographic features?

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

      Indirect_Spatial_Reference: Florida Bay

    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 0.01. Longitudes are given to the nearest 0.01. Latitude and longitude values are specified in Decimal degrees.

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257.

  7. How does the data set describe geographic features?

    Entity_and_Attribute_Overview:
    The following parameters are shown for the samples: fractions, intervals, location of sample, analyses, and sections with no sample remaining referenced to site name
    Entity_and_Attribute_Detail_Citation: USGS personnel

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?

    Marci Marot and Bowdewjn Remick assisted in the analysis of the samples.

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

    Debra A Willard
    U.S. Geological Survey
    926A National Center
    Reston, VA 20192

    703 648 5320 (voice)
    703 648 6953 (FAX)
    dwillard@usgs.gov

Why was the data set created?

The use of radioactive isotopes is founded on the known physical property of radioactive material, the half-life. A half-life of an isotope is the amount of time it takes for half of a given number of atoms to "decay" to another element. The age of objects that contain radioactive isotopes with known half-lives can be calculated by determining the percent of the remaining radioactive material. To use this method successfully certain other prerequisites must be met. These are: 1. the chemistry of the nuclide (element) is known; 2. once the nuclide is incorporated into the substrate the only change is radioactive decay, and 3. in order to be useful, it is relatively easy to measure.

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)
    Long cores (>1 m in length), were taken in >30 cm of water through the "moon pool" of a motorized 25 ft pontoon barge either grounded on the bank or anchored with 4 anchors. The location was established by GPS. A portable 12 ft high tripod was placed over the moon pool to hold the coring piston and for extraction of the core. Cores were taken with 10.8 cm-diameter, clear, FDA food grade polycarbonate tubing. A PVC piston with two O-ring seals was used. The piston was pushed into the bottom of the core tube to a position several cm above the bottom of the tube. A 10 m length of .25 cm diameter braided polypropylene line, attached to a ring threaded into the top of the piston, was pulled through the core tube. The core tube was then carefully lowered through the moon pool and any air trapped in the space between piston and the bottom of the core tube was removed and filled with water. When the tube was several cm above the bottom, the free end of line attached to the piston was affixed to the head of the tripod. Thus when the core tube penetrates the sediment, the piston remains in a fixed position a few cm above the sediment surface producing a vacuum that retards compaction. When the apparatus was set in position, the core tube was quickly thrust about 30 cm into the sediment by hand. Next, an aluminum clamp with handles was fixed to the core tube and two people then forced the core barrel in until it reached the underlying Pleistocene limestone. Next the clamp with handles was removed and a clamp with lifting rings was attached near the air/water interface. A cable through a pulley at the top of the tripod and attached to a hand winch mounted on one leg of the tripod was attached to the lifting ring on the clamp. The cable winch was necessary for extraction due to the weight of the core and strong suction created by the mud. Before extraction, the polypropylene line was removed from the tripod and fixed to the extraction clamp. This was to ensure that the piston remained in a fixed position during extraction and to retard loss of sediment from the bottom of the barrel. A benefit of the clear core tubing was that any leakage around the piston's O-ring seal could be readily observed during the extraction process. A person in the water wearing a face mask observed the core tube to be certain no sediment was lost at the sediment/water interface, to record any elevation difference between the sediment surface inside and outside the core at full penetration, and to quickly place a plastic pipe cap on the bottom of the core as it emerged from the sediment. The core was winched above the surface of the moon pool and lowered to rest vertically on deck. The pipe cap was taped tightly to the tube to prevent leakage. Excess tubing was cut off just below the piston using a large pipe cutter so the piston could be carefully removed without disturbing the sediment surface. In some cases the water above the sediment was carefully siphoned off with a tube to prevent sloshing of water during transport to the laboratory which would disturb the sediment surface. In other cases the piston was left in the core tube during transport. All cores were transported vertically. Each evening cores were transported vertically to a local hospital where X-ray photographs were prepared.

    The cores were selected for analysis based on the x-rays. Those cores selected for further analysis were selected on the basis of laminations or other features which indicated the lack of disturbance. The core was placed in an extruding device vertically. The core was then extruded up into a template and sliced. This slice (hockey puck) was place on a preweighed titanium plate and the wet weight determined. The ring was then removed and the slice was trimmed to remove the outer portion of the core. This was done to prevent any contamination that may have occurred at the side of the core barrel during the coring operation. This sample was then bagged and weighed. This weight was found to be important in the determination of water content and thus the dry weight as water was lost during the period of initial sampling and the laboratory analysis. These sample were then stored in a refrigerator and then transhipped to the home based laboratory. For those core selected for trace metal analysis, the slices were sampled from the center of the "hockey puck" with titanium tools and place in an acid washed plastic bottle and frozen.

    Person who carried out this activity:

    Debra A Willard
    U.S. Geological Survey
    926A National Center
    Reston, VA 20192

    703 648 5320 (voice)
    703 648 6953 (FAX)
    dwillard@usgs.gov

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

    Gough, L. P. Kotra, R. K.; Holmes, C. W., 2000, Regional Geochemistry of Metals in Organic-Rich Sediments, Sawgrass, and Surface Water from Taylor Slough, Florida: USGS Open-File Report 00-327, U.S. Geological Survey, Reston, VA.

    Online Links:

    Holmes, Charles W. Robbins, John, Halley, Robe, 2001, Sediment dynamics of Florida Bay mud banks on a decadal time scale: Bulletins of American Paleontology 361, Paleontoligical Research Institution, Ithica, NY.

    Other_Citation_Details:
    in Paleoecological studies of South Florida

    Bruce Wardlaw, editor

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

  1. How well have the observations been checked?

  2. How accurate are the geographic locations?

    The location of sample sites was established by GPS.

  3. How accurate are the heights or depths?

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

    Not all sites have information for all the data parameters

  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: none
Use_Constraints:
None. Acknowledgement of the U.S. Geological Survey would be appreciated for products derived from these data.

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

    Heather S.Henkel
    U.S. Geological Survey
    600 Fourth St. South
    St. Petersburg, FL 33701
    USA

    727 803-8747 ext 3028 (voice)
    727 803-2030 (FAX)
    hhenkel@usgs.gov

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

    Florida Bay Sample Core Log

  3. What legal disclaimers am I supposed to read?

    The data have no implied or explicit guarantees

  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 31-Oct-2007
Metadata author:
Heather Henkel
U.S. Geological Survey
600 Fourth Street South
St. Petersburg, FL 33701
USA

727 803-8747 ext 3028 (voice)
727 803-2030 (FAX)
sofia-metadata@usgs.gov

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

This page is <http://sofia.usgs.gov/metadata/sflwww/hlmscsmp.faq.html>

U.S. Department of the Interior, U.S. Geological Survey
Comments and suggestions? Contact: Heather Henkel - Webmaster
Generated by mp version 2.8.18 on Wed Oct 31 16:35:33 2007