Thermoluminescence dating sediments
It uses various methods to stimulate and measure luminescence.It includes techniques such as optically stimulated luminescence (OSL), infrared stimulated luminescence (IRSL), and thermoluminescence dating (TL).These methods also do not suffer from overestimation of dates when the sediment in question has been mixed with “old carbon”, or -deficient carbon that is not the same isotopic ratio as the atmosphere.In a study of the chronology of arid-zone lacustrine sediments from Lake Ulaan in southern Mongolia, Lee et al.The older the sample is, the more light it emits, up to a saturation limit.The minerals that are measured are usually either quartz or potassium feldspar sand-sized grains, or unseparated silt-sized grains.
For example, in quartz a short daylight exposure in the range of 1–100 seconds before burial is sufficient to effectively “reset” the OSL dating clock.
There are advantages and disadvantages to using each.
For quartz, blue or green excitation frequencies are normally used and the near ultra-violet emission is measured.
This is usually, but not always, the case with aeolian deposits, such as sand dunes and loess, and some water-laid deposits.
Quartz OSL ages can be determined typically from 100 to 350,000 years BP, and can be reliable when suitable methods are used and proper checks are done.