M. Járó - L. Költő szerk.: Archaeometrical research in Hungary (Budapest, 1988)
Dating - BENKŐ Lázár: Thermoluminescence dating of Hungarian archaeological sites (potteries, hearths, calcite)
BENKŐ Lázár* THERMOLUMINESCENCE DATING OF HUNGARIAN ARCHAEOLOGICAL SITES (POTTERIES, HEARTHS, CA LCI TE) Abstract - Principles and basic techniques of thermoluminescence dating, an efficient tool for obtaining absolute archaeological chronologies, are outlined. The researches carried out in the Institute of Isotopes during the last decade resulted in the adaptation and refinement of the quartz inclusion method. The essential features of these investigations are summarized. Experimental procedures (TL measurement, determination of the components of annual dose , error assessment) are discussed, as well as some of the recent applications to date potteries and findings produced by industrial archaeology (smelting-hearths, fired clay). Preliminary results related to materials of geological origin (calcite) are presented. Introduction Nuclear physics is experiencing an increasing impact on archaeometry. The methods for providing absolute archaeological chronologies are generally based on radioactivity. The first revolutionary contribution was due to radiocarbon dating. In the last two decades a new technique known as thermoluminescence (TL) dating has evolved as an extension of the principles using TL phenomena in nuclear radiation dosimetry [1]. In this paper the principles and basic techniques of TL dating will be outlined. Then we describe some of our results which were obtained in the adaptation and refinement of the quartz inclusion method to potteries of prehistoric origin, smelting-hearths and fired clay. Preliminary investigations on materials of geological origin (calcite) will be presented as well. Principles of TL dating Most minerals possess the ability to emit light at temperatures below the red-glow, usually in the interval from 200-400 °C. This weak light emission, called thermoluminescence, is related to the release of trapped electrons from crystal lattice imperfections to lower energy levels, the trapped electron probabilities being first created by ionization caused by trace amounts of radioactive impurities. The inclusion technique, one of the methods of pottery dating by means of TL, is based on the phenomenon that mineral inclusions such as quartz and feldspars, which are embedded in the clay matrix, have a much higher sensitivity to "acquire TL" than the matrix itself. On the other hand, the TL observed is a measure of the cumulative dose of radiation to which the inclusions have been exposed since the previous heating. In the case of pottery the event dated is the firing by ancient man (Fig. 1 ). The accumulated radiation dose and hence the natural TL induced in mineral inclusions originate from alpha, beta and gamma radiations from uranium and thorium chains and potassium which are invariably present in the clay .When the pottery gets buried, radiation from the surrounding soil also adds to the continuous build-up. The shallow traps of the crystal lattice will continuously fade as even they are being continuously irradiated, but the deeper traps giving rise to TL peaks from 300 to 400 °C continue to build up without any fading. •institute of Isotopes of the Hungarian Academy of Sciences H-1525 Budapest, P.O.B. 77
