摘要
1 Dicellograptus divaricatus rigidus zone (bed 257--227): This is a new fauna afterthe Nemagraptus gracilis fauna. The fauna is characterized by an abundance of long androbust Dicellograptids, such as Dicellograptus divaricatus rigidus, D. divaricatus and D.divaricatus robustus as well as short and slender Corynoides curtus. Orthograptid of thecalcaratus group, Dicranograptus nanus, D. brevicaulis, Pseudoclimacograptus scharenbergiand very abundance Climacograptus such as C. parvus. C. haddingi etc., and
A continuous section of Hanjiang and Shikou stages of Ordovician is well exposed at Shuangjiakou of Qidong County, S. Hunan. Over a hundred thousand specimens of grapt-olites were obtained during this field work. Shuangjiakou Formation (bed 256-140) was established by the authors (1979) with the type section located at Shuangjiakou of Qidong. It overlies conformably the Baimachong Formation and underlies conformably the Chengbu Formation. This formation is lithologically divided into three parts, the lower part, black thin-bedded carbonaceous shale intercalated with black siliceous rocks and bedded chert, the middle part, siliceous shale with mid-beJded chert (bed 205-202) with a Fe-Mn bed (bed 201), and the upper part, black siliceous rocks with thin-bedded siliceous shale, weathering greyish white in colour. Four fossil zones may be distinguished: 5. Climacograptus spi-niferus zone (lower part), 4. Dicranograptus clingani zone, 3. Climacograptus wilsoni zone, 2. Climacograptus bicornis zone and 1, Dicellograptus divaricatus rigidus zone, Chengbu Formation (bed 139-1) was estabished by the authors (1979), with its type locality at Daliang-tou, Chengbu county, S. Hunan, It overlies conformably the Shuangjiakou Formation and underlies conformably the Tianmashan Formation. This formation is lithologically divided into two parts, the lower part, composed of black laminated carbonaceous striped mudstone intercalated with a few thin-bedded siliceous shale, and the upper part, consisting of black moderately thick-bedded striped mudstone, weathering yellow and intercalated with a few yellowish-green mudstone (bed 51-47). Three fossil zones may be recognized: 7. Dicellograptus johnstrupi zone, 6. Climacograptus pygmaeus zone and 5.Climacograptus spiniferus zone (upper part).
出处
《地层学杂志》
CSCD
北大核心
1989年第3期161-192,共32页
Journal of Stratigraphy
基金
湖南省地质矿产局科研基金
