The biggest amount of oak wood investigated by the Laboratory was collected from the riverine sediments in the research site Smurgainys (Smarhoń in Belarusian). The research site is located approximately 85 km to the south east from the Lithuanian capital Vilnius and 52 km to the present state border of Lithuania. Trunks of oak were excavated in 1960-1970s during the exploitation of a gravel pit, located on the bank of r. Neris-Vilija, approximately 10 km to the East from the Smurgainys town (Битвинскас, 1978; 1984). The trunks were buried in the gravel by the fluctuations in the river bed (Битвинскас, 1974; 1978). It is no doubt that River Neris frequently changed its watercourse. During the field-work the abrasion of the eastern bank was observed (Битвинскас, Кайрайтис, 1975). Trunks were excavated in huge amounts. Besides oak, wood of conifers was also identified, but was not collected and investigated. The trunks are variable in size; some samples exceed 1.5 m in diameter. Samples were found in the 3-8 m. depth and usually extracted with the remains of stump ad big roots. The picture shows the trunk of oak investigated by co-workers of the Laboratory.
In the Soviet period, a part of samples were dated in various laboratories: University of Tbilisi, Ural Pedagogical Institute, and at the Institute of Botany in Vilnius (Битвинскас et al., 1978; Битвинскас, 1984). At present, the majority of samples were dated by using a liquid scintillation spectrometer. The dates were calibrated calendar years by using OxCal 4.1.7 program (Bronk Ramsey, 2001) with the IntCal09 calibration curve (Reimer et al. 2009).
97 samples, comprising of 75% of the total number of collected cross-sections, according to the results of cross-dating and radiocarbon dates were arranged into 17 groups; each group containing from one to 25 series. The oldest tree grew approximately 5782–5612 BC (floating series) and the youngest AD 1606–1778. The longest gap according to radiocarbon dates exist between 3060 and 1100 BC with a short sample around 1800–1900 BC.
A very good agreement between some samples (30 out of 97), indicates a possibility of duplicates in the collection, i.e. several samples were taken from the same trunk. The duplicates are characterized by very good visual agreement; correlation values range 0.70–0.94, similarity 72–94%, and t-value 9.6–34.8. The chronology No. 16 was absolute dated against East Pomerania (T. Wazny, Poland), Vilcuro1 (R. Pukienë, Lithuania), and Baltic1 (I. Tyers, UK) chronologies to AD 778–1325. Hence, the chronology was shifted by 32 years backwards in time. Furthermore, the chronologies shows good agreement to Northern Germany chronologies constructed from imported Baltic timber (S. Wrobel, personal communication).