贵州扬子地层区晚三叠世双壳类生物地层

Late Triassic Bivalve Biostratigraphy of Yangtze Stratigraphic Province，Guizpou

根据贞丰龙场、毕节青场等上三叠统剖面上双壳类的垂直分布，结合区域资料，将贵州扬子地层区晚三叠世双壳类划分为8个生物地层单位。自下而上为：①Halobikui-"Daonella"bifurcata组合带；②Halobiarugosoides延限带;③Halobiarugosoides-Costatoriakwei-Chowensis间隔带；④Costatoriakweichowensis延限带；⑤Trigonoduskeuperinus顶峰带；⑥yun－nanophorusboulei组合带；⑦Indosinion-Permophorus组合带；⑧Qiyangia顶峰带。又根据双壳类的生态类型及赋存岩石的沉积特征，将贵州扬子地层区晚三叠世双壳类分为4个群落：①Halobia群落；②Costatoria群落；③Yunanophorus群落；④Qiyangia群落。上述4个群落在剖面上由下而上的演替，反映在晚三叠世时，贵州扬子地层区处于持续上升的海退过程中。

<Abstrct> According to vertical distribution of Bivalve at Upper Triassic sections inLongchang of Zhenfeng and in Qingchang of Bine, Late Triassic Bivalve of Yangtzeprovince, Guizhou is divided into 8 biostratigraphic units, i.e., in ascending order,1. Halobia Kui- 'Daonella' bifurata Ass. zone, 2. Halobia rugosoides Ran. zone, 3.Halobia rugosoides - Costatoria kweichowensis inter. zone, 4. Cosatoria kweichowensis ran. zone, 5. Trigonodus keuperinus Ac. zone, 6. Yunnanophorus bouleiAss. zone, 7. Indosinion- Premophorns Ass. zone and 8. Qiyangia Ac. zone. Also,based on ecological types of Bivalve and dePOSitional features of their host rocks, LateTriassic Bivalve of Yangtze Province, Guizhou can be classified into, in ascending order, four communities of Halobia, Costatoria, Yunnanophorus and Qiysngia. Theyevolved from lower to upper in these ctions, renecting that Yangtze stratigraphicprovince of Guizhou during Late Triassic was in regression.