Facilities - Luminescence Dating Laboratory - Methods
Luminescence dating is an alternative to radiocarbon dating, when no organic material (bone, seed, wood, etc.) is available, or if the expected age is greater then the limits of radiocarbon dating of about 40,000 years. It is even useful for times beyond the calibration range for radiocarbon ages, where luminescence techniques provide comparable error estimates.
Luminescence dating can be applied to establish the age of archaeological or geological sites, by dating ceramics or rocks (must have been heated) or certain soils or sediments. These materials contain minerals (mainly feldspar and quartz), which are extracted and used for dating.
Aim of the MPI-EVA Luminescence Dating Laboratory
This laboratory is intended to provide chronometric ages especially for Palaeolithic sites. The age information which can be deduced from human remains and typological/technological analyses of artefacts is often rather limited. This is especially true for the Middle Palaeolithic, the time of the Neanderthals. Any model on e.g. the disappearance of Neanderthals and the arrival of modern humans in Europe must be based on age estimates of individual archaeological sites. While geological and palaeoclimatological data sometimes provide precise age information, a more accurate age can be determined by chronometric dating methods. Many dating methods are often not applicable either to range limitations (e.g. too old for 14C), or the scarcity of material suitable for dating. Either heated material or sediment for luminescence dating is usually abundant in Palaeolithic sites. Luminescence dating methods thus provide, among others, the framework for the interpretation of human evolution.
The underlying principle is the storage of energy in the crystal lattice of minerals, due to the presence of natural ionising radiation in the environment. With time, increasing energy is stored in the mineral, which is partially released as luminescence (light), when the material is heated or exposed to sunlight. In principle, the older a sample, the longer it had been exposed to radiation and the more luminescence (light) could be released. Hence, the luminescence is proportional to the radiation the mineral has received. This radiation is released at a steady rate, thus providing a clock for the age calculation
Luminescence methods allow the dating of samples up to several hundred thousand years. Within this time period, the ‘Luminescence Clock’ had to be set to zero by exposure to heat (in a prehistoric fire) or sunlight. All the energy stored is thus released (zero) and starts to accumulate again due to the environmental radiation, until released and measured as luminescence in the laboratory (Fig). Only because of this zeroing in the past, the age of a ceramic, rock or sediment can be established.
Two main methods have to be distinguished
- Thermoluminescence (TL), where the sample is heated (ceramics, heated rocks, sediment)
- Optically Stimulated Luminescence (OSL), where the sample is exposed to light (sediment, soil)
In general, the method used for measuring the luminescence in the laboratory is similar to the way the ‘Luminescence Clock’ had been set to zero in the past.
More information on Luminescence Dating and the MPI-EVA Luminescence Dating Laboratory
[download our PDF leaflet here]