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Proteins contain from 50 to several hundred amino acids.
All of the amino acids which occur in proteins, except for glycine, which is the simplest amino acid, have at least one asymmetric carbon atom, and can exist as one of two possible stereoisomers.
Thus, it will be possible not only to describe the sediment age, but also to give a picture of the dominant mixture of plankton alga at the same time.
Sediment studies may also be supplemented with determinations of e.g. Method Decay of uranium in the earth's crust releases the gas radon.
The 210Pb dating may be supplemented with dating of the caesium 137Cs isotope.
This isotope was released in huge quantities in connection with the atmospheric nuclear explosions in 1963 and later by the Tjernobyl accident in 1986.
A number of studies have focused on the accumulation of heavy metals during the past 100 years.
The naturally lead isotope 210Pb may be used to date aquatic sediments and peat bogs.
The method is suitable for dating approximately 100 years back.
In addition to the mentioned rates, the dating may also give a picture of the stability of the sediments and thus tell whether the chronology of the layers is intact or whether the activity of the benthic fauna has changed the chronology by bioturbation.
Local changes of current conditions may also cause changes of the chronology of the layers.