FOSSIL WOOD ASSEMBLAGE FROM THE UPPERMOST WUTONGGOU LOW-ORDER CYCLE (CHANGHSINGIAN-INDUAN) OF SOUTH TAODONGGOU, BOGDA MOUNTAINS, NORTHWESTERN CHINA

The end-Permian mass extinction is the most dramatic biotic crisis of the Phanerozoic, when 95% of the marine species and 75% of terrestrial species were wiped out. Fossil plants are crucial to understand the terrestrial ecological diversity, dynamics of terrestrial environmental changes, and processes of biological evolution. The rarity of continuous Permo-Triassic continental records, especially in the mid-latitude of northern Pangea, has limited documentation of floral successions and their response to the geological events. Systematic studies on fossil woods can identify the composition of past vegetation. This study has documented a relatively diverse fossil wood assemblage in the uppermost Permian-Lower Triassic of south Taodonggou, Bogda Mountains in NW China. Multidisciplinary data including U-Pb ID-TIMS zircon dating, organic carbon isotope chemostratigraphy, and cyclostratigraphic correlation indicate that the fossil bearing interval is of latest Changhsingian or earliest Induan in age. Standing (autochthonous) trunks are mainly composed of Protophyllocladoxylon sp.1 with coniferous affinity. Transported assemblage (allochthonous) contains Arthropitys sp., Agathoxylon sp., Amyelon sp., and Protophyllocladoxylon sp. 2. Growth rings are commonly absent in those woods. When present, they are faint with less than 5-cell wide latewood. Growth pattern in fossil woods indicates relative stable environmental and climatic conditions in Taodonggou during the latest Changhsingian or earliest Induan. Further research will provide evidence to support or reject the current model on the response of woody landscapes to the end-Permian extinction event.