DATING EARLY MEDIEVAL CERAMICS BY THE THERMOLUMINESCENCE METHOD: BUSÓWNO SITE CASE STUDY (Próba datowania ceramiki wczesnosredniowiecznej metoda termoluminescencji: przyklad badan zespolu grodowego w Busównie)
The Early Medieval stronghold in the Lublin voivodeship was explored archaeologically in 2004–2005. The site, which lies in the riverside zone of the Swinka river, comprises ring-shaped ramparts encircling an area of 7 ha trenches were dug through two of the ramparts, in the inner area of the stronghold and on the so-called mound. The stratigraphical data combined with dendrochronological and radiocarbon dating have confirmed a two-phase development of the site in the tribal (9th-10th century) and early statehood (12th-13th century) periods. Large ceramic assemblages were recovered from the deposits explored in particular features. Seven sherds were dated by the thermoluminescent (TL) dating method. In Polish research, the method is usually applied at the intercrossing of archeology and geology pleistocene deposits. The possibility of dating of younger deposits has generated little interest so far, mostly due to a sustained belief in a still extensive error margin that has made the method less than effective for the middle ages. TL age is the quotient of the archaeological dose (AD) and the annual dose (DR). Radioisotope concentration measurements were made by the gamma spectrometric method for parts of the mineral deposits with a mass of about 600 g and pottery samples weighing from 60 to 100 g in the form of round plates c. 60 mm in diameter. TL age estimates confirmed the two-phase chronology of the ceramic selected material. The dating for all ceramic samples from group 1 fell within the time range between A.D. 717 and 1102 . In four cases the results ranged between A.D. 717 and 947 falling within the chronological timeframe assumed for group 1. An interesting experiment was the 'double' dating of sample Lub-4350, giving a TL age estimate of A.D. 784-928 compared to 14C dating of A.D. 860-1000. These dating appears promising at this early stage of the research providing two kinds of information: concerning the firing date of a given vessel and a potential dating of the context. At the present stage of the research, the scope of effective TL method usefulness for dating Early Medieval ceramics cannot be fully evaluated. The analyses series is still too small on a site which has yet to be investigated comprehensively.The TL age estimates obtained for the site have been burdened with an error margin of 6-7%, allowing them to be correlated with the results of 14C and dendrochronological dating. There are still many limiting factors at this stage of the research, resulting from the method's imperfections as well as from the little attention paid to contextual data: further close and continuous cooperation between the archaeologist and the physicist is demanded. The TL age estimates obtained for the stronghold are a reason for optimism, leading one to express the hope that the method will soon be accepted as an effective dating technique for Early Medieval as well as prehistoric materials. 7 Figures, 4 Tables.
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