Thermoluminescence dating of sand dunes in rajasthan
For quartz, blue or green excitation frequencies are normally used and the near ultra-violet emission is measured.For potassium feldspar or silt-sized grains, near infrared excitation (IRSL) is normally used and violet emissions are measured.It includes techniques such as optically stimulated luminescence (OSL), infrared stimulated luminescence (IRSL), and thermoluminescence dating (TL)."Optical dating" typically refers to OSL and IRSL, but not TL.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.Feldspar IRSL techniques have the potential to extend the datable range out to a million years as feldspars typically have significantly higher dose saturation levels than quartz, though issues regarding anomalous fading will need to be dealt with first.The minerals that are measured are usually either quartz or potassium feldspar sand-sized grains, or unseparated silt-sized grains.
This is usually, but not always, the case with aeolian deposits, such as sand dunes and loess, and some water-laid deposits.
The radiation causes charge to remain within the grains in structurally unstable "electron traps".
The trapped charge accumulates over time at a rate determined by the amount of background radiation at the location where the sample was buried.
It is useful to geologists and archaeologists who want to know when such an event occurred.
It uses various methods to stimulate and measure luminescence.