Analysis on Fossil Charcoals from the Oligocene Qaidam Basin，China and its implications

This study conducted a systematic taxonomic investigation of fossil charcoal from the Oligocene Shangganchaigou Formation in the Qaidam Basin. This formation is a key research medium for reconstructing the co-evolution of biota and environment during the uplift of the Tibetan Plateau. Fossil charcoal serves not only as a direct proxy for ancient wildfire activity but also as a source of high-resolution anatomical evidence for paleo-vegetation reconstruction, providing crucial clues for revealing regional paleoecological dynamics. Based on SEM analysis of the radial sections, this study proposes a new anatomical classification system suitable for fragmented fossil charcoal. This system hierarchically categorizes charcoal remains into 2 major classes, 5 subclasses, 5 econd-order Subcategories, and 6 minor classes. Applying this system revealed that the fossil charcoal is predominantly composed of tracheids with bordered pits, which are typical features of gymnosperm conifer wood. These findings anatomically confirm that during the Oligocene conifer trees were already present in the Qaidam Basin. They also provide direct evidence for interpreting the structure of contemporary paleo-vegetation and paleoclimatic conditions. This study deepens our understanding of the Paleogene paleoecology and paleo-wildfire history in northern Tibetan Plateau and establishes a standardized methodological framework for anatomical classification and comparative analysis of fossil charcoal in similar sedimentary environments.