Carbon dating live mollusk
In certain parts of the globe, the equatorial region in particular, deep waters move up.
This phenomenon is latitude dependent and occurs as a consequence of trade winds.
Coastline shape, local climate and wind, and ocean bottom topography also contribute to upwelling.
Upwelling is another phenomenon that dilutes radiocarbon content of surface waters.
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.
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.