贺兰山北段石炭纪和二叠纪植物群

CARBONIFEROUS AND PERMIAN FLORA IN THE NORTHERN PART OF THE HELAN MOUNTAINS

贺兰山北段石炭纪和二叠纪植物化石经鉴定,计有39属104种。讨论了植物群的性质,划分了5个组合,即(1)晚石炭世早期Bothrodendroncirculare—Mesocalamitescistiformis组合;(2)晚石炭世中期Lepidodendronsubrhombicum—Conchophyllumrichthofenii组合;(3)晚石炭世晚期Lepidodendronszeianum—Neuropterisovata组合;(4)早二叠世早期Lepido dendronposthumii—Callipteridiumkoraiense组合和(5)早二叠世晚期Caulopteriswudaensis—Paratingiadatongensis组合。这5个组合的代表岩组分别为红土洼组、羊虎沟组、太原组下部、太原组中上部和山西组。其地质时代大致相当于纳缪尔B—C期、维斯发期、斯蒂芬期、阿赛尔期、萨克马尔期和阿丁斯克期。植物群含有大量的华夏型分子,为典型的华夏植物群。此外还讨论了植物群的演化。

The fossil plants studied in this paper were collected from the Carboniferous and Permian strata in the northern part of the Helan Mountains. The flora is composed of 104 species in 39 genera, which may be divided into five plant assemblages in ascending order as follows:(1)the early Late Carboniferous Bothrodendron circulare-Mesocalamites cistiformi assemblage;(2)the middle Late Carboniferous Lepidodendron subrhombicum-Conchophyllum richthofeni assemblage;(3)the late Late Carboniferous Lepidodendron szeianum-Neuropteris ovata assemblage;(4)the early Early Permian Lepidodendron posthumii-Callipteridium koraiense assemblage;(5)the late Early Permian Caulopteris wudaensis-Paratingia datongensis assemblage. Their typical formations are the Hongtuwa Formation, the Yanghukou Formation, the Lower Taiyuan Formation, the Middle and Upper Taiyuan Formation, and the Shanxi Formation respectively. The geological ages of the five plant assemblages may approximately correspond to the Namurian B-C, Westphalian, Stephanian, Asselian, Sakmarian and Aritinskian. The Carboniferous and Permian flora contains typical Cathaysian elements and it is a typical Cathaysia flora. The flora can be compared with contemporaneous floras in the Cathaysian province. In addition, the evolution of the flora is discussed in this paper.