Recent radiocarbon dating

Sending wet or frozen samples for radiocarbon dating is fine.The lab starts the analyses immediately upon arrival of the sample so moisture will not induce contamination.paleobotanist for plants, forensic archaeologist for bones, or paleontologists for shells.Generally, it is better to date the macrofossils present than the sediment due to the possible contaminants in the latter.This is mostly true for sediments that are organic rich (dark black or brown in coloration) as well as for sediments that are not well drained and where water ponds (like swamps, peat bogs, etc).

The source of this carbon can be from more recent humic and fulvic acids or ancient labile carbon that is alkali-soluble.For such sediment samples, when you date both the sediment and some plant material that is found in the sediment, the dates are usually very similar thus sometimes there is really no humic acid problem to worry about.When sediments yield older ages than the plant (macrofossil), it is usually due to two possible reasons:(1) the plant remains were somehow intrusive (grew into the older sediment, perhaps due to erosion or long periods of low or no soil development), or(2) the sediment was getting some or all of its carbon during its formation from an older source (reworking or redeposition of already deposited sediment from upslope due to flooding, mass movements or other physical processes).Sediment geochemistry is very complex and can change from area to area even over small distances.Usually it is recommended to date the macrofossils that are found whenever possible, provided the researcher thinks that the macrofossils are “in-situ” and did not grow from the overlying layers (like roots).

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