###### Abstract
The vast majority of studies after 2000 focused on the dating of subfossil wood by dendrochronology and other methods [15; 16] or dating in conjunction with material characterisation [17; 18; 19]. The most investigated species of subfossil wood were as follows: oak, elm, ash, pine, fir, etc. Oak (_Quercus_ spp.) seems to be the prevalent subfossil wood discovered and studied in Europe, especially in East and Central Europe [2; 4; 9; 10; 11; 17; 18; 20; 21; 22; 23]. A particular interest in subfossil oak has been evident in research carried out in the Czech Republic [2; 3; 4; 17; 18; 24], Poland [9; 15], Serbia [21], Bosnia Herzegovina [5], Italy [22; 23], Austria [16], and Germany [14]. The complex physical and chemical modifications, in terms of loss of structural chemicals or tissue integrity [24], occurring in wood during the long sub-fossilisation process are reflected in changes in the physical and mechanical properties compared to recent wood [2; 3; 4; 5; 6]. Density is a physical property of wood largely investigated in correlation with anatomical structure and mechanical properties due to its practical importance for processing and treating technologies. Several researchers reported slightly reduced values of the basic density of subfossil oak compared to recent wood (e.g., 91% of the value of recent wood according to [22]). It was also observed that density does not necessarily decrease with the age of subfossil oak, but it depends on the location of burial, condition of deposition and degree of degradation of wood components [2; 13]. When archaeological oak excavated from fluvial terraces was investigated, a higher density than contemporary wood was obtained, and the author explained that this result is due to a strong supersaturation of wood with mineral compounds [20]. Values of basic density almost equal to those for recent oak, without noticeable differences between internal and external areas of the subfossil trunk, were reported for subfossil oak from Italy [23]. The oven-dry density reported by different authors varied in the ranges of 544-667 kg/m\({}^{3}\) for new wood [25] and 526-668 kg/m\({}^{3}\) for subfossil oak [3]. Increased dimensional instability was reported for subfossil oak. Double values of shrinkage and swelling compared to recent oak and the fact that these values did not change with the age of subfossil wood were reported [2]. Similarly, an increased affinity for water and almost double swelling values compared with recent oak were found by other researchers [4; 24]. The same increasing trend of wood shrinkage with double radial values or even triple tangential values compared to recent wood was registered in another research [23]. In terms of mechanical properties, it was stated that compression strength parallel to the grain of subfossil oak does not exceed the value of 40 MPa, being approx. 25-50% lower than the strength of recent wood [2; 3; 14; 20]. A similar trend, but with a lower decrease of about 10-23%, was also reported [23]. Despite all these general trends, the properties of subfossil oak woody are highly variable, depending on the burial conditions, composition of the environmental sediments and age of the material, though this seems to be not the most relevant influencing factor. Therefore, chemical investigation of subfossil wood is necessary to explain the changes in properties [2; 4; 24]. In Romania, subfossil wood is almost unknown to users. However, researchers have recently studied subfossil wood of various species discovered on Romanian territory, focusing mainly on dendrochronological evaluation [26; 27; 28] or some specific chemistry-related characteristics [6; 10; 11; 29]. Subfossil oak from the Suceava region was investigated by dendrochronology [28], while chemometric characteristics of historical/archaeological oak from the 14 th century, wood-water relationship and biological degradation of subfossil oak were also research topics [6; 10; 11].