Thermoluminescent dating of the remains of ancient Estonian settlements by means of feldspar inclusion method

K-feldspars were extracted from burnt sand from under the hearths of ancient settlements. Energetical trap parameters with Tm = 320°C (heating rate 2.5 grad/sec) were determined: E = 1.7 eV; T = 3.2 · 108 years. Fading was not observed within the limits of reproducibility ( < 5 %). The impact of etching with acids on TL and dosimetric properties of feldspars were studied. As quartz proved unapplicable to TL-dating K-feldspars were used for determining the age of some ancient Estonian settlements. The results obtained are in good agreement with radiocarbon dates and archaeological suppositions

Possible reasons for anomalous fading in alkali feldspars used for luminescence dating of Quaternary deposits

According to many publications, alkali feldspars are characterized by specific athermal (anomalous) fading of their thermoluminescence and optically-stimulated luminescence. This phenomenon is manifested as spontaneous decline in luminescence intensity over relatively long (months and years) time after laboratory irradiation, possibly due to tunnelling of electrons from lattice defects and impurities acting as dosimetric traps. It can hamper reliable luminescent dating of Quaternary deposits on the basis of feldspar extractions due to possible unpredictable underestimation of the ages. In this paper we present some experimental results related to the manifestation of the phenomenon. It is found that, in general case, the assumed long-term anomalous fading cannot be connected to electron tunnelling from the deep dosimetric traps. At the same time, some decrease in the dosimetric luminescence signal observable in just irradiated feldspar samples can really be caused by tunnelling. However, the probability of this process quickly goes down, already within some days after irradiation. Interpretation of some other short- and long-term anomalous fading-like effects requires involvement of radiation- and thermo-induced ionic processes

Новые геохронологические данные по неоплейстоцен-голоценовым отложениям Западного Таймыра и островов Карского моря

We consider the new radiocarbon and uranium-thorium dating of deposits of Western Taimyr and the islands of the Kara Sea, made from organic material (wood, peat, mollusk shells) and dating performed on the sandy sediments by infrared optical stimulated luminescence (IR-OSL). The greatest number of datings obtained from marine terraces sediments, correlated with Karghinskiy (MIS 3) horizon. The deposits containing peat and wood, mostly have Holocene age. Accumulative ridges Mikhailov Peninsula (Western Taimyr) correlated with Zyryanian (MIS 4) horizon and represented by ancient marine beach ridges.Рассмотрены новые радиоуглеродные и уран-ториевые датировки отложений Западного Таймыра и островов Карского моря, выполненные по органическим остаткам (древесина, торф, раковины моллюсков), а также датировки, выполненные по песчаным отложениям методом инфракрасной оптико-стимулированной люминесценции (ИК-ОСЛ). Наибольшее количество датировок, полученных по отложениям морских террас, коррелирует с каргинским (МИС 3) горизонтом. Отложения, содержащие торф и древесину, в основном — голоценового возраста. Аккумулятивные гряды на полуострове Михайлова (Западный Таймыр) коррелируют с зырянским (МИС 4) горизонтом и являются древними морскими береговыми валами