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Luminescence dating is good for between a few hundred to (at least) several hundred thousand years, making it much more useful than carbon dating.
The term luminescence refers to the energy emitted as light from minerals such as quartz and feldspar after they've been exposed to an ionizing radiation of some sort.
This pushed the calibration back beyond recorded history almost to 10,000 BP (years before the present.) One valuable source of samples of various ages came from a bristlecone pine tree called "Methuselah" in the White-Inyo mountain range of California.
Samples from the tree were able to generate calibration points back to that date. It is narrow or broad, depending upon whether the weather during that year was dry or wet, and whether the tree was exposed to various stressors.
Luminescence dating (including thermoluminescence and optically stimulated luminescence) is a type of dating methodology that measures the amount of light emitted from energy stored in certain rock types and derived soils to obtain an absolute date for a specific event that occurred in the past.
The method is a direct dating technique, meaning that the amount of energy emitted is a direct result of the event being measured.
Two forms of luminescence dating are used by archaeologists to date events in the past: thermoluminescence (TL) or thermally stimulated luminescence (TSL), which measures energy emitted after an object has been exposed to temperatures between 400 and 500°C; and optically stimulated luminescence (OSL), which measures energy emitted after an object has been exposed to daylight.
To put it simply, certain minerals (quartz, feldspar, and calcite), store energy from the sun at a known rate.
The possibility of making use of TL stored in a mineral or pottery sample was first proposed by chemist Farrington Daniels in the 1950s. The potential of using thermoluminescence to date buried soils developed on colluvial and fluvial sediments from Utah and Colorado, U.
Minerals—and, in fact, everything on our planet—are exposed to cosmic radiation: luminescence dating takes advantage of the fact that certain minerals both collect and release energy from that radiation under specific conditions.
Crystalline rock types and soils collect energy from the radioactive decay of cosmic uranium, thorium, and potassium-40.
Better still, unlike radiocarbon dating, the effect luminescence dating measures increases with time.
As a result, there is no upper date limit set by the sensitivity of the method itself, although other factors may limit the method's feasibility.
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The tree ring sequence adjacent to the slab's bark matched the sequence near Methuselah's core.