ABSTRACT
To be used for dating, the ESR signal sites must be sensitive to background radiation, so that the signal intensity is directly proportional to the natural dose rate, and must have lifetimes at least an order of magnitude greater than the age of the sample. The sites must also be robust (not subject to fading other than the thermal effect) and must not have been recrystallized or otherwise affected so that the number of traps is changed. Most, but not all, ESR-datable materials are carbonates or phosphates and are zeroed at the time of deposition because they were freshly crystallized. Materials that meet the above criteria are usually tooth enamel, speleothems (stalagmites and the like), mollusc shells, or corals. The lifetimes of ESR signals in these materials are close to or greater than 1.0 Myr, and all are radiation sensitive and relatively stable. Zeroing due to heating is also possible for flint or other siliceous artifacts.
