内蒙古乌达煤田石炭—二叠系约1500 m厚, 含40余层煤线或煤层, 而6号、7号煤层之间的火山凝灰岩的高精度定年时代为298.34 Ma (相当于阿瑟尔初期), 这为提升传统植物大化石组合序列的年代精度奠定了基础。 本文利用乌达煤田露天开采揭露太原组地层的机遇, 对8号—15号煤层间的地层开展古植物群落与埋藏学研究, 探索植物与环境的协同演化关系, 发现植物化石六层, 系统采集鉴定14属26种。根据沉积环境及植物古生态学分析, 识别出该地区上石炭统太原组植物群落面貌属于典型的中期华夏植物群组合。其中12号煤底板、12^上 号煤底板、10号煤和9号煤底板下伏地层发现的化石为异地埋藏, 反映泻湖及海岸周边低地和高地植物群落面貌; 而8 号煤顶板发现的植物化石为原地埋藏或亚原地埋藏, 反映成煤沼泽初期的植物群落面貌。对比12号煤底板、12^上 号煤底板和10号煤及9号煤底板下伏地层植物化石的差异, 表明在12^上 号煤和10号煤之间植物化石有着较大的变化, 可作为太原组两个植物化石组合的界线。对比8号煤顶板和6号、7号煤之间火山凝灰岩中的植物化石, 表明8 号煤顶板碎屑岩中的植物化石主要反映成煤沼泽末期的植被面貌, 而与凝灰岩中保存的生长于成煤沼泽中期的植被差异显著。

The Wuda Coalfield in Inner Mongolia yields over 40 coal seams within approximately 1500-meter-thick strata spanning from the Carboniferous to the Permian. The high-precision dating of volcanic tuff between No. 6 and No. 7 coal seams indicates an age of 298.34 Ma, nearly on the Carboniferous-Permian boundary. Taking advantage of the well exposure of the Taiyuan Formation in the Wuda Coalfield through open-pit mining, fossil plants have been extensively collected from No. 8 to No. 15 coal seams. Six plant-fossil bearing beds have been recognized, and 26 species of 14 genera of fossil plants have been identified. Based on sedimentological analyses, the plant assemblages of the upper Carboniferous Taiyuan Formation have been constrained well in palaeoecology, showing a typical phase of the middle stage of the Cathaysia Flora. The underclay of coal seams Nos. 12, 12^upper, 10, and 9 contain allochthonous plant fossils that indicate vegetation growing nearby the peat-forming swamp, whereas the roof shale of coal seam No. 8 yields autochthonous or parautochthonous plant fossils that represent the last phase of the coal-forming vegetation. The floristic difference between the floor beds of coal seams No. 12 to No. 9 may indicate that there exists the boundary of the traditionally well-known lower and upper plant assemblages of the Taiyuan Formation between coal seams No. 12^upper and No. 10. Moreover, the floristic difference between the roof shale of coal seam No. 8 and the volcanic tuff sandwiched between coal seams No. 7 and No. 6 indicates that the main peat-forming plants may vary with environmental changes during different stages of coal swamps–fossils in the underclay or roof shale may reflect the peat-forming vegetation or surrounding plant communities during the early or late stages of peat formation, whereas fossils found in the mid-stage of peat formation may differ in composition.

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