西秦岭关家沟组晚奥陶世苔藓植物孢子和陆生维管束植物小孢子化石

西秦岭文县东峪口—关家沟一带分布的关家沟组为一套粗碎屑流和浊流沉积组合,因缺乏古生物化石,其形成时代长期存在争议。在文县关家沟滴水岩剖面中、下部4件灰色粉砂质板岩样品中分离并鉴定出了晚奥陶世苔藓植物孢子(隐孢子)(cryptospores)和陆生维管束植物小孢子(miospores)化石8属18种(包括未定种)、疑源类(acritarchs)8属10种、几丁虫(chitinozoa)3属4种和虫颚(scolecodonts)3属3种,这些微体化石的地质时代相当于西欧Carodoc-Ashgill阶。在这些样品中发现苔藓植物孢子和早期陆生维管束植物小孢子,不仅是中国奥陶纪地层中首次发现和报道,而且也为研究早期陆生植物演化提供新的直接依据。

A new record of the Late Ordovician cryptospores and vascular plant miospores from Guanjiagou Formation, West Qinling

The Guanjiagou Formation is exposed extensively in West Qinling, Gansu Province. The Guanjiagou Formation is mainly composed of slightly metamorphosed clastic rocks, and its age is a topic of controversy. 8 genera and 18 species of cyptospores and miospores, 8 genera and 10 species of Acritarchs, 3 genera and 4 species of chitinozoa and 3 genera (3 species) of scolecondonts were recognized. The oldest geologically well-dated spore tetrads and cuticlolike sheets of cell have been recovered from the Guanjiagou Formation, Wenxian County, Gansu Province. This is the first record of genera and species in China, and is the earliest known occurrence of land plant spores in China. The species is a typical Late Ordovician element known currently from Europe, Africa, North America and South America. The age of the cryptospores and miospores may also be Late Ordovician, equivalent to the Caradocian and Ashgillian.