10Be for Surface exposure dating (SED)
The first, exemplified by the K-Ar, Rb-Sr, and U-Th methods, makes use of the buildup of daughter products from primordial radionuclides. The second approach uses the decay of cosmogenic isotopes that are produced in the atmosphere and the incorporated into terrestrial reservoirs. Examples of this approach include standard sup. C and sup. Be dating. We now describe a third approach: measurement of the buildup of cosmogenic radionuclides in geological materials exposed to cosmic rays at the earth’s surface. Whereas the firs two techniques measure the time since the object to be dated became a geochemically closed system, the third technique measures the time of the object’s exposure on the surface of the earth. Therefore, this method should allow chronologies to be established for presently undatable geomorphic features as well as for certain materials that can be dated only with difficulty by means of the first two techniques for example, low-potassium volcanic rocks less than , years old. Radionuclides useful for cosmogenic buildup dating should have half-lives sub. Possible candidates include sup.
