Optically stimulated luminescence dating determines when a material was last exposed to light or heat. In this case, we are concerned with quartz and the effects on it from nuclear radiation. The effect measured is due to a cumulative distortion in the distribution of electrons in the quartz crystals. When as a result of light application the distortion is released there is an emission of light, the intensity of which can be measured. If the amount of radiation required to produce the natural signal is known, and a history of radiation incident upon the sample can be constructed, then the date at which the signal was last reset can be determined.
De Vaux (1973) subdivided the periods of occupation at Qumran into five different phases starting in the 8th century BC and ending in 135 CE. De Vaux's chronology has, however, been challenged by archaeologists. Material from three locations was sampled, including: (1) brick from a kiln in loc.101, (2) silt from wall fill of water installation loc.118, and (3) two samples of silt from the sedimentary fill of loc. 71.
Results:
Loc. 101 (pottery-kiln): Age 590 ± 130 BC. The date indicates that Qumran
was occupied during Iron Age II
Loc. 118 (water installation): Age 200 ± 120 BC. This date indicates
that the water instillation of loc. 118 was constructed during the Hasmonean
period.
Loc. 71 (water installation): 1. Age 1270 ± 50 AD; 2. Age 1440 ±
40 AD. These dates suggests that installation loc. 71 was kept clean, and remained
in use, as late as ca. 1270 AD (Mameluke period).