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.
When it is necessary to extract carbonates by drilling or powdering specific areas of the material (especially those suspected to be very old – greater than 20 ky), we recommend that the drilling be done under an inert gas (like N2, Ar, etc.) and that the material be stored in very small vials and sent to us without delay.
Shells can be categorized as marine, estuarine, or riverine.
Analysts in AMS labs need to know the type of shell they are dealing with in order to establish the potential contaminants and determine the methods to remove them.
The marine effect is a consequence of the slow mixing between surface waters and deep waters in the oceans.
The rapid exchange of carbon between the atmosphere and the biosphere via the carbon dioxide pathway is not exactly the same between the atmosphere and the oceans.
You are welcome to contact us to discuss the pretreatment or request that we contact you after the pretreatment (and prior to dating).
This protein makes up only a few percent of the shell, hence the sample needed in the radiocarbon dating process is the inorganic portion.This carbon exchange usually affects the shell’s exterior.Recrystallization, on the other hand, can affect even the inner layers of a shell.Coastline shape, local climate and wind, and ocean bottom topography also contribute to upwelling.The slow mixing and the upwelling of deep waters mean that the surface water of oceans already have apparent radiocarbon age relative to the atmosphere.In certain parts of the globe, the equatorial region in particular, deep waters move up.