If the material is quite old (20 ky), it is possible that long-term exposure to the atmosphere can bias the result in the more recent direction by some unknown degree.
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– Fees are inclusive of d13C and d18O measurements done in an isotope ratio mass spectrometer (IRMS), quality assurance reports, calendar calibration when applicable, and 24/7 web access to past results and pending analyses.
– It is important to understand the pretreatment applied to samples since they directly affect the final result.
You are welcome to contact us to discuss the pretreatment or request that we contact you after the pretreatment (and prior to dating).
– AMS dating requires as little as 3 milligrams of coral after the pretreatment.
Shells are not easy to radiocarbon date; there are many factors that contribute uncertainties to the results.
American physical chemist Willard Libby, a pioneer of the radiocarbon dating technology, predicted shells to be the least effective materials to radiocarbon date.Shells can be categorized as marine, estuarine, or riverine.However, we recommend 50-100 milligrams be sent to allow for an aggressive cleaning prior to the dating (and repeat analyses if necessary for confirming results based on quality control measures, at no additional cost to the client).Most shells, corals, and other carbonate materials are cleaned by physical abrasion to remove the outer surfaces and any adhering carbonate material and are then acid etched to remove approximately 10-30% or greater of the total weight so that only the good primary carbonate is dated.– Please take note that exposure to atmospheric carbon dioxide (CO2) may affect the radiocarbon dating results.It has been shown that powdered carbonates will absorb atmospheric CO2 due to the very large surface area.