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Xenoxylon is an important boreal Mesozoic fossil wood genus and has been widely reported from sites across northern China. This paper reports well-preserved Xenoxylon wood from the Jurassic-Cretaceous boundary Tuchengzi Formation at Yanqing, Beijing, China. The fossil wood described here is ascribed to two species, i.e. Xenoxylon latiporosum and X. peidense. The present new finding enrichs our knowledge of the floral characteristics, especially the forest composition of the Tuchengzi Formation. These new records enlarge the fossil wood diversity of the genus Xenoxylon of the Tuchengzi Formation up to three species at Yanqing. Statistic results of the annual and mean sensitivity values of the X. latiporosum and X. peidense indicates that the trees inhabited under a sensitive climate with relatively stable interannual water supply. Additionally, some fungal remains represented by fungal hyphae were found with wood tissues of specimens of X. peidense. Typical wood rotting structures resembling those of the extant white rot are also found in X. latiporosum. This is the first record of fungal hyphae in Yanqing, Beijing, China, and provides us with new evidence that can be used to explore interactions between fungi and plants in the Late Jurassic. Institutional abbreviations: YQ = Yanqing Silicified Wood National Geopark, Beijing, China [ABSTRACT FROM AUTHOR]

Classifications and comparisons of petrified wood are currently based primarily on observable morphologies. The mineralogical characteristics of specimens collected from Qian Jiandian, Yanqing UNESCO Global Geopark, Beijing, China and Sigri, Lesvos Island UNESCO Global Geopark, Greece, were compared in this study to enhance the conservation and protection of Chinese petrified wood. Comparisons were carried out on the basis of internal structural observations using a polarising microscope, x-ray diffraction (XRD), and analysis of major and trace elements. Results show that structures and main chemical components (SiO2) remained almost the same between samples while organic carbon and numerous trace elements (e.g. As, Cu, Mo, Zn) were significantly different. The approaches employed at Lesvos will require modifications in future work, including adjusting adhesives and solvents for different climates, selecting conservation sites and methods based on different preservation conditions, and determining appropriate cleaning methods and agents according to different petrified wood components. The results of this analysis lay the theoretical foundation for petrified wood conservation in Yanqing. Work at this site is the first model study for the preservation of petrified wood in China and creates new opportunities for related research. [ABSTRACT FROM AUTHOR]