Charles W. Holmes (retired) Debra Willard, Unknown, Florida Bay core logs disposition and analysis parameters.Online Links:
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.
Marci Margot and Bowdewjn Remick assisted in analysis of the cores.
703 648 5320 (voice)
703 648 6953 (FAX)
dwillard@usgs.gov
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.
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:
703 648 5320 (voice)
703 648 6953 (FAX)
dwillard@usgs.gov
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.
Bruce Wardlaw, editor
The location of sample sites was established by GPS.
Information is provided for all the cores used in the study. The list was revised 10/29/1997
not applicable
Are there legal restrictions on access or use of the data?
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- None. Acknowledgement of the U.S. Geological Survey would be appreciated for products derived from these data.
727 803-8747 ext 3028 (voice)
727 803-2030 (FAX)
hhenkel@usgs.gov
Florida Bay Core Logs Disposition and Analysis Parameters
The data have no implied or explicit guarantees
Data format: | MS Excel Size: 0.02 |
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<http://sofia.usgs.gov/exchange/holmes/holmescores.html> |
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727 803-2030 (FAX)
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U.S. Department of the Interior, U.S. Geological Survey
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