36Cl is produced in the atmosphere by spallation of 36Ar by interactions with cosmic ray protons.In the top meter of the lithosphere, 36Cl is generated primarily by thermal neutron activation of 35Cl and spallation of 39K and 40Ca.The next few pages cover a broad overview of radiometric dating techniques, show a few examples, and discuss the degree to which the various dating systems agree with each other.
The ages calculated from the chlorine ratios are generally concordant with those from the other methods, implying the constancy of the chlorine input ratio over the last million years.
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Trace amounts of radioactive 36Cl exist in the environment, in a ratio of about (7-10) × 10−13 to 1 with stable chlorine isotopes.
This corresponds to a concentration of approximately 1 Bq/(kg Cl).
The half-life of this nonreactive isotope makes it suitable for geologic dating in the range of 60,000 to 1 million years.
Additionally, large amounts of 36Cl were produced by irradiation of seawater during atmospheric detonations of nuclear weapons between 19.Furthermore, the negative charge of the chloride anion discourages adsorption onto silicate surfaces, which are also typically negatively charged.Due to this behaviour, chloride, once introduced to natural water, is usually advected at the same rate as the water and is not normally removed from the water by geochemical processes.NOTE: We only request your email address so that the person you are recommending the page to knows that you wanted them to see it, and that it is not junk mail. Chlorine has two stable isotopes and one radioactive isotope: the cosmogenic isotope 36Cl. 36Cl decays primarily (98%) by beta-minus decay to 36Ar, and the balance to 36S.We try to avoid rocks with high chlorine concentrations because of the complex Cl).