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The Louisiana Radiocarbon Database
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The Louisiana radiocarbon database that you will be searching today is based on the original Louisiana radiocarbon database published in 2001 (McGimsey and Van der Koogh) and has been updated to include published radiocarbon dates from December 1999 onward. One of the goals of the database, in addition to making the information more accessible to the public, is to keep the information as up-to-date as possible. As new cultural resource management reports that contain radiocarbon dates are added to our library, the dates will be entered into the database. In some cases, dates may be published in other venues such as newsletters, journals and dissertations that would not necessarily be sent to our office. In rare cases, the dates may have never been published. It is our hope that researches will share their radiocarbon dates with us via the Louisiana Radiocarbon Date Submittal Form. This form can also be used for reporting errors you may find in the database, providing additional information about a date (such as the correction factor that may not have been provided in the published reference) or recalibration of dates.
A few changes have been made to the original database, notably the database is now offered online and is searchable using the following fields: site name, site number, LA Division of Archaeology report number, lab number, date BP (before present), and date range BP. Fields from the original database that have been maintained are material, provenience, measured radiocarbon age, C12/C13 (now headed as correction factor), conventional radiocarbon age (CRA) BP, Calibrated (Cal) median B.C. /A.D., Calibrated (Cal) BP, Calibrated 2 sigma range (BP), cultural component, and comments. Fields added to the database are the LA report number, calibration reference (if known), and references (all known references on a date not just the primary reference). For ease of use and for those who may not be familiar with radiocarbon dating a brief description of each of these terms follows:
- Site Name
- The name of the archaeological site as it appears on the official Louisiana Site Record Form.
- Site Number
- Each archaeological site in Louisiana is assigned a unique number consisting of three parts. For example 16AV1, (this is the site number for the Marksville site in Avoyelles Parish. 16 = state designation number, AV= parish abbreviation, 1= sequential number assigned to site with the parish.
- Reported contextual information on where the sample was obtained. The following abbreviations are used throughout database: Md. = mound; Str. = structure (house); Sq. = square; PM = posthole or postmold; Fea. = feature; TU = test unit; hz = horizon. Depths are given as cm bs (centimeters below surface) or cm/ft/in bd (centimeters, feet, inches below datum).
- Lab Number
- Each radiocarbon date has a unique lab number. The lab number consists of the Lab Code (abbreviation associated with a radiocarbon dating lab, for example Beta Analytic = Beta) followed by a number. For a complete list of lab codes referred to in the database see http://www.radiocarbon.org/Info/labcodes.html
- Type of material dated. Examples include charcoal, shell, wood, nuts, seeds, etc.
- Measured Radiocarbon Age
- This is sometimes referred to as the raw age and represents the uncalibrated radiocarbon date. This date is not always referenced in the database due to the fact that it may not have been referenced in the publication.
- Correction Factor
- A C13/C12 correction factor, applied to the measured raw radiocarbon age, to adjust the date for fluctuation and variation in the carbon isotope ratios as a result of natural biochemical processes and non-natural causes, was not used until the late 1980s. The earlier radiocarbon dates in this database were calculated using an estimated correction factor. These dates will be represented with an asterisk (*) after the number in the correction factor field. It should be noted that calibrated dates using an estimated correction factor may result in an unreliable calibrated date. In some cases of earlier reported dates it is unknown whether the date provided was a conventional date or a measured radiocarbon date. In those circumstances, the error in the calibrated date may be even greater.
- Conventional Radiocarbon Age (CRA)
- Each record in the database should have a conventional radiocarbon age. The conventional date is the raw/measured radiocarbon date that has been normalized to the modern standard through the use of C13/C12 correction factor. Always use this date and the associated correction factor when calibrating or recalibrating a date. This date will remain constant, whereas calibrated dates will change depending on the calibration curve used to calculate them. The date is presented in years before present (BP). In radiocarbon dating present refers to 1950!
- Calibrated Median (BP)
- This is also known as the intercept between the radiocarbon age and the calibrated calendar scale curve. In some samples there may be multiple median dates. The date is presented in years before present (BP). In radiocarbon dating present refers to 1950!
- Calibrated Median (B.C./A.D.)
- Same as above but the date is presented in Roman calendar years.
- Calibrated 2 Sigma Range
- This represents a statistical confidence interval where there is a 95% probability that the actual date falls within this date range. The date is presented in years before present (BP). In radiocarbon dating present refers to 1950!
- Comments are taken directly from references.
- LA Report Number
- This is the Louisiana Division of Archaeology report number. Not all references will have a number.
- Calibration Reference
- The calibration program used to produce the calibrated medians and calibrated 2 sigma ranges. This is the reference for the calibrated dates presented in the table. Other references may have used a different calibration program and the published dates may vary slightly.
How to Use the Louisiana Radiocarbon Database
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The website offers five basic ways to search the database. You can search records by site number, site name, lab number, LA report number or by specific date (BP) or date range (BP). If you do not know the entire site name or lab number, etc., the search function will operate with a partial field entry. The database can also be searched for a specific date or date range. It is important to remember that all dates entered must be in BP years and that the dates that will be queried are the conventional radiocarbon age (CRA) which will include the +/- year range. Date or date range searches may also be restricted to a specific parish. The decision not to include a calibrated date search was based on the fact that the calibrated dates are subject to change depending on the calibration program used and the continual improvements in the calibration curve.
The results window will display the following fields: site name, site number; lab number; conventional radiocarbon age; LA report number; and view. All search results can be sorted by site name, site number, lab number, conventional radiocarbon age, or LA report number. By clicking the view button, a full display of all the record for a specific date will appear. There will be blank fields. If there is no information within a field it means that we were not able to obtain that information from the publication(s). We hope that there are no errors in the reporting the dates but unfortunately this is never the case. If you come across an error please let us know.
Citing Dates Presented in this Database
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When referencing a date from this database use the references provided for the individual dates and not the database. We suggest when referencing radiocarbon dates that you use the Society of American Archaeology guidelines (section 3.3.5 Radiometric Ages and Dates).
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If you require more information, have comments regarding the radiocarbon database or have a more specific query that cannot be performed by the online version, please contact the Louisiana Division of Archaeology at 225-342-8170.
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Copies of this publication can be obtained through the Louisiana Archaeological Society website
- McGimsey, Charles R. and Josetta van der Koogh
- Louisiana's Archaeological Radiometric Database. Special Publication of the Louisiana Archaeological Society No. 3. Baton Rouge.