###### Abstract  
Subfossil oak (SO) wood material, originating from three different buried trunks discovered in recent years by excavations in riverbanks on Romanian territory, was analysed in this research. Aged oak recovered from constructions (AO_C) and recent/new oak wood material (NO) were also investigated to provide comparative data for the SO. The oven-dry density and the basic density, the total volumetric and linear swelling and shrinkage coefficients and the compression strength parallel to the grain were the selected physical and mechanical properties considered. The experimental results showed a lower density of SO compared to NO and AO_C tested by up to about 19-20%, alongside a trend of increased dimensional instability, with variability among the tested assortments. The compression strength parallel to the grain was reduced by 19-31% compared to NO. The properties of AO-C were closer to those of NO, but differences between wood materials from different sources and of different ages were registered. A positive linear correlation was found between compression strength parallel to grain and the basic density for all types of material and assortments tested. These comparative results have to be considered by designers and engineers in the valorisation of SO in furniture design and other applications. oak; subfossil wood; aged wood; recent wood; density; swelling; shrinkage; compression strength Article  
Selected Physical and Mechanical Properties of Subfossil Oak (_Quercus_ spp.) Compared to Aged Oak and Recent Oak  
(Quercus spp.) Compared to Aged Oak and Recent  
storage have a significant effect on the ageing process, generally defined as a slow, gradual and irreversible alteration of the chemical and physical structure of the material under the action of environmental factors. When wood has been stored indoors, in dry air, where no significant variation in temperature, UV radiation or water contact were present, the ageing effect on the structure and wood properties is minimal if no biodegradation was present. Contrarily, if the wood has been exposed outdoors, complex chemical degradation by UV radiation, thermal degradation, erosion and biological deterioration may occur [7]. Different chemical processes are responsible for the ageing of external surfaces and sub-surfaces, with an important contribution of light, especially UV radiation causing lignin degradation, compared to inner bulk wood in the absence of light, where hemicelluloses are the most affected [8]. Nevertheless, chemical and properties changes are not limited to the surface of wood (e.g., colour, roughness), but mechanical properties can also be affected by ageing in oxic conditions under variable conditions of temperature and relative humidity. Interest in recovering and valorisation of aged wood from constructions in innovative furniture design has grown in recent years, so acknowledging the changes in properties compared to recent wood is important. Discovering subfossil buried wood during excavation work in riverbeds or riverbanks, or archaeological work in various sites, has raised scientific interest, leading to intensified research in this field [9]. Subfossil wood might be also found as archaeological wood, raising the scientific interest of both restorers in the field of Cultural Heritage and wood scientists in direct relation to its historical significance, specific properties and conservation challenges [6; 9; 10; 11; 12]. Regarding the study of subfossil wood worldwide, a rather limited number of papers were published before 2000. Some of them focused on defining and understanding the phenomena of ageing and fossilization of wood or material dating by dendrochronology [1], while others referred to the physical and mechanical properties of the material [13; 14]. The interest in subfossil wood has continuously grown in conjunction with the progress of investigation methods and equipment.