Luminescence dating is commonly used to determine sediment ages. The method is based on the principle that certain minerals in sediments accumulate a luminescence signal during burial, e.g. when they are covered by other sediment layers. This luminescence signal is induced by radioactive elements such as Uranium, Thorium or Potassium, found in any sediment. With the radioactive decay of these elements, energy is released which can be absorbed within the crystal lattice of minerals such as quartz or feldspars. The energy absorption occurs as redistribution of electrons from lower to higher energy levels. If the quartz or feldspar grains within a sediment body are then exposed to daylight, e.g. by aeolian or fluvial transport, the absorbed energy is released as light, i.e. as photon emission. The former build up of the luminescence signal is set to zero in this process. If the minerals are covered by further sediment layers, the luminescence signal will continue to accumulate again.
If samples are taken from the sediment (without exposing the sample to sunlight!) the luminescence signal can be stimulated using light (Optically Stimulated Luminescence) or heat (Thermoluminescence), and then measured using a photomultiplier to detect the signal. If the luminescence intensity, which serves as measure for the energy absorbed and hence for the burial time, is divided by the rate of environmental radioactivity, the time of the last exposure to daylight, and so a burial age, can be determined.
Aeolian sediments, in the form of dune sands or loess, are best suited to luminescence dating as complete resetting of the signal during transport can be expected. Despite a different transport history it is still possible to accurately date fluvial and glaciolacustrine deposits, as well as colluvial and tsunami deposits.
The time span covered by this dating method ranges from a few tens of years up to about 300 ka. The maximum age limit can vary considerably and is highly dependent on the material characteristics of the measured mineral grains and the size of natural activity in the surrounding sediment.
