Several tens of subfossil oak samples from riverine sediments and bogs were investigated by the Laboratory in the last decades. Unfortunately, the radiocarbon dates are dispersed over the whole Holocene, which does not allow us to construct a millennia-length oak chronology for Lithuania.
Subfossil oaks excavated in the vicinity of Smarhoń (Belarus) have been at the attention of scientists since the 1960s (Битвинскас et al., 1972). The research site is located approximately 85 km to the southeast of the Lithuanian capital Vilnius and 52 km to the present state border of Lithuania. Trunks of oak were excavated in the 1960–1970s during the exploitation of a gravel pit located on the bank of River Neris (Viliya), approximately 10 km to the east of the Smarhoń town (Битвинскас et al., 1978; 1984). The trunks buried under the gravel by the meandering river (Битвинскас, 1974; 1978) were excavated in huge amounts. In addition, during the field-work, the abrasion of the eastern bank was observed (Битвинскас and Кайрайтис, 1975). Besides oak, the wood of conifers was also identified but not collected. The trunks were of variable size; some samples exceeded 1.5 m in diameter. They were found at 3–8 m depth and usually pulled out with remains of the stump and big roots. The picture above from the archive of the Laboratory shows the trunk of oak investigated by co-workers of the Laboratory.
In the Soviet period, a part of the collected samples was dated in various laboratories, such as the University of Tbilisi, Ural Pedagogical Institute and the Institute of Botany in Vilnius (Битвинскас et al., 1978; Битвинскас, 1984). However, initial difficulties were caused by the lack of precise radiocarbon dates and missing oak reference chronologies in the Baltic region (Битвинскас et al., 1978; 1984). Currently, most samples are redated by the Radioisotope Research Laboratory at the Nature Research Centre in Vilnius.
One hundred and twenty-two samples preserved at the depository of the Laboratory were made available for the study. According to radiocarbon dating, the oldest oak grew from 5782–5612 calBC. Radiocarbon and dendrochronological dating of 97 samples allowed us to construct ten mean curves (containing 2–9 series) and three chronologies (10–25 series). According to radiocarbon dates, the longest gap exists between 2987 and 1137 calBC, with a short sample around 1900–1817 calBC. The high deposition rate of oak trunks was recorded in 4191–3830 cal BC, 1137–716 calBC, 320 calBC – calAD 162, calAD 190–421 and calAD 246–556. The longest chronology (No. 16), covering 549 years, was absolutely dated against various oak chronologies of Polish/Baltic origin to AD 778–1326. Furthermore, the chronologies show good agreement with the chronologies of northern Germany constructed from imported Baltic timber (S. Wrobel, personal communication).
In addition, a high 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 characterised by very good visual agreement; correlation values range from 0.70 to 0.94, the similarity from 72 to 94 % and the t-value from 9.6 to 34.8.