However, many times what happens is the opposite; the alkali-extracted sediment yields a younger date due to the factors above.
Beta Analytic’s Recommendation: When alkali extractions and dating on either the humic or humin fractions or sediments are requested, the lab recommends that the researcher considers getting three dates for at least one sample prior to dating a larger number of samples, provided all of the samples submitted are from the same unique depositional area and geochemistry.
If you want to dry your samples, heating at 90°C to 100°C for 4-24 hours is recommended.
If macrofossils are found, the lab will inform the researchers and they can decide if they want to date the macrofossils or sediment.
In some cases, it is wise to date both separately to see if the macrofossils or sediment is yielding the best (most reliable) date.
In general the plant dates are usually more reliable as they typically represent a more unique event in time.
The plants were relatively short-lived as compared to the time it may have taken for the sediment to form.
This can be useful information if a large core or sequence of cores are being dated.