Pliocene taxodiaceous fossil wood from southwestern Ukraine and its palaeoenvironmental implications

Mineralized wood collected from Late Pliocene strata near Gorbki village in the Transcarpathian region of Beregovo Kholmogor'e in southwestern Ukraine was anatomically studied and identified. The wood possesses distinctive anatomical features and has distinct growth rings with an abrupt transition from early-to late-wood. Wood consists of tracheids with 1-3 seriate, dominating bi-seriate, opposite pits on the radial walls and taxodioid cross-field pitting, indentures present. Rays are uni-seriate and 1 to 73 cells high. Ray parenchyma horizontal walls thin and smooth. Axial parenchyma distributed in early-and late-wood and is solitary and diffuse, with end walls nearly smooth or slightly nodular. The combination of features observed in the wood indicates it belongs to the conifer family Taxodiaceae and is most similar to modern Sequoia and assigned to the fossil genus Sequoioxylon. Comparison with species of Sequoioxylon show it is most similar to Sequoioxylon burejense, but ray tracheids were not found in our specimens. We describe the specimens here as Sequoioxylon cf. s. burejense noting this similarity. Extant Sequoia is distributed in the northern California coastal forest eco-region of northern California and southern Oregon in the United States where they usually grow in a unique environment with heavy seasonal precipitation (2500 mm annually), cool coastal air and fog drip. This study supplies magafossil evidence of Sequoioxylon as an element of the Late Pliocene forest community in Ukraine and indicates a climate with heavy seasonal precipitation and fog drip.