烟叶大羽羊齿Gigantopteris nicotianaef olia Schenk的时空分布和相关地层的对比

TEMPORAL AND SPATIAL DISTRIBUTION OF GIGANTOPTERIS NICOTIANAEFOLIA SCHENK AND CORRELATION OF RELATED FORMATIONS

烟叶大羽羊齿Gigantopteris nicotianaef olia Schenk是地质和古生物工作者熟知的植物化石。由于Halle(1927)曾将单网羊齿的种误归并于这一种内,致使它一度成为广见于华夏古植物区二叠纪陆相地层的植物化石。后来的研究表明(GuandZhi,1974;姚兆奇,1983;Glasspooletal.,2004),除了河南平顶山的可疑标本外(Sze,1954),此种可作为华南冷坞期的标志性植物。最新资料证实(杨关秀等,2006),产自河南禹州和临汝上石盒子组(云盖山组)的标本完全显示了G.nicotianaef olia的特征,说明了这个种在华北的存在,从而扩大了这种植物的分布区。根据烟叶大羽羊齿的时空分布规律,文章认为河南的上石盒子组完全可与江苏龙潭组和江西乐平组老山段下亚段的含煤层位对比,时代应属瓜德鲁普世冷坞期(Capitanian)。文中较详细阐述将河南上石盒子组的时代定为冷坞期而不是晚二叠世早期(吴家坪期)的观点,并引证磁性地层方面证据,支持这一结论。

Gigantopteris nicotianaefolia Sehenk is a well-known Permian index plant fossil. Due to the misleading concept of the species introduced by Halle （1927）, this species was once believed to be widely spread in the Cathaysian phytogeographical realm. The subsequent studies （Gu and Zhi, 1974; Yao, 1983; Glasspool et al., 2004）, however, revealed that G. nicotianaefolia may serve as an index fossil of Capitanian age in South China. Some specimens from Henan of North China have been questionably assigned to G. nicotianaefolia. Lately, Yang and others （2006） were able to identified some specimens from western Henan as G. nicotianaefolia since they displayed almost all the main characteristics of this species. This eventually confirms the occurrence of this species in North China and thus expands its distribution to North China. Based on the temporal and spatial distribution of G. nicotianaefolia, it is proposed that the Upper Shihhotse Formation of Henan can be correlated to the coal-bearing beds of the Lungtan Formation of Jiangsu and the Lower Sub-member of the Laoshan Member of Jiangxi, South China. Supported by the magnetostratigraphical data, it is further suggested that the Upper Shihhotse Formation should be Capitanian rather than Wuchiapingian （early Late Permian） in age.