There are two components involved in evaluating age by luminescence. One is the equivalent dose determined from luminescence measurements on mineral crystals (usually quartz or feldspar) extracted from the material to be dated. The other is the dose rate to which the crystals have been exposed throughout antiquity. The age is then the ratio (equivalent dose)/(dose rate). Factors which influence the accuracy of the two components, and so the accuracy of the age, are discussed. Limiting factors are identified in order to recognize aspects of measurement on which future development must concentrate to achieve an improvement in accuracy of age determination.
A beta irradiation unit is described which contains a 4 GBq90Sr source. The shielding, comprising perspex, aluminium and lead is designed to provide an acceptably low doserate to the user without exceeding a manageable mass as it is necessary to move the shielded source while in use for thermoluminescence dating. The cylindrical shield is 192 mm in diameter and 192 mm high and has a mass of 33 kg. Measurmeents of bremsstrahlung spectra from the system are reported and interesting features noted. A comparison of the bremsstrahlung dose-rates as determined by three different portable dose-rate monitors is also presented.
We present measurements of Thermoluminescence (TL) from Greek marble quarried at Paros, Naxos, Pendeli, Hymitos, Thassos,
which have been known since ancient times. The results concern i) the solar bleaching of TL, ii) the solar transmission through
marble thicknesses up to 16 mm, and iii) the implications for potential dating of ancient carved marble monuments/objects.
The bleaching rate for marbles is very fast during the first hour of exposure. The solar penetration is at least 35 mm for
long exposures. Beyond the 2 mm marble slab for exposure times 90–120 hours of sunshine, the residual bleached TL level is
not reached. The bleached TL reaches a plateau which serves as the “zero time” upon which the archaeological TL dose subsequently
builds up and gives the age of a marble monument.
Authors:I. Liritzis, R. Galloway, and P. Theocaris
Two archeological ceramic sherds in a single quartz aliquot form have been dated success-fully for the first time, by the newly developed method of optical stimulated luminescence (OSL) with green light-emitting diodes (LED). Comparison with the conventional thermoluminescence (TL) method provided ages of the same order of magnitude. The ceramics come from two recently excavated sites at Hellenikon and Ligourio in Argolid, Peloponnese, Greece. One sherd dates from the end of 4th millenium B.C., while the other is classified around 7th c. B.C.. The new method of nuclear dating is described in the paper and appropriately evaluated.
For age determination, the single aliquot regenerative-dose (SAR) method was applied to quartz from archaeological materials, using luminescence stimulated by blue light. The quartz samples were extracted from sediment from the hydroponic farm related to rice cultivation in an area of archaeological interest in Buyeo, south of Seoul. The optically stimulated luminescence (OSL) dates obtained offered good agreement with the ages derived by typological assessment and 14C ages. These ages should contribute significantly to interpretation of the history of rice cultivation in Korea.
Authors:D. Hong, S. Yi, R. Galloway, and T. Tsuboi
The single aliquot additive dose method of equivalent dose determination was applied to quartz from heated archaeological materials, using luminescence stimulated by blue light. The quartz was extracted from pieces of pottery and kiln in an area of archaeological interest in Suwon region, south of Seoul, Korea. The dates obtained were in good agreement with the ages derived by archaeological evidence. It is concluded that the additive dose single aliquot method of determining equivalent dose, with correction for re-use of the aliquot, should contribute significantly to optically stimulated luminescence dating procedures, particularly when the amount of sample separated is limited. Additionally, some luminescence images from quartz samples using a CCD camera are presented and relationships between AGTL, TL and OSL are discussed.