First record of a petrified gymnospermous wood from the Kungurian (late Early Permian) of the southern Sydney Basin, southeastern Australia, and its paleoclimatic implications

For the first time, a silicified wood with well-preserved inner structures is reported from the Kungurian (Early Permian) Snapper Point Formation in the southern Sydney Basin, southeastern Australia. It is characterized by uni- to tetraseriate araucarian radial tracheidal pits and large, simple cross-field pitting. This wood is attributed to Protophyllocladoxylon dolianitii Mussa 1958, and it is assumed to be of cordaitalean affinity, which is one of the dominant and arborescent element of the early Permian Gangamopteris Taiga. Evidence of growth patterns of the fossil wood, and the paleogeographical reconstruction shows that the host tree of the fossil wood was growing in a strongly seasonal polar light regime. The wide growth rings (5.315–12.316 mm) and the large number of tracheids per ring (99–288) indicate the tree flourished under favorable conditions during the growing season, with ample water and clement temperatures, enhanced by the extended daylight hours of the Antarctic-type summer. The occurrence of frost rings in the wood, corroborated by additional sedimentological information suggest that unusual climatic events (aperiodic cold and freezing events) occurred in terrestrial ecosystems of the southern Sydney Basin during the Kungurian. The study demonstrates that fossil wood of exceptional preservation, like the one reported here, can offer valuable and potentially unique information crucial for deep-time paleoclimatic reconstruction.