江西上饶朝阳磷矿新元古代晚期陡山沱组微体化石新材料

NEW MICROFOSSILS FROM THE LATE NEOPROTEROZOIC DOUSHANTUO FORMATION AT CHAOYANG PHOSPHORITE DEPOSIT IN JIANGXI PROVINCE, SOUTH CHINA

江西上饶朝阳磷矿新元古代晚期微体化石产于上震旦统陡山沱组上部含磷地层中 ,微体化石组合包括疑源类Asterocapsoidessp .,Megasphaerainornata ,Meghystrichosphaeridiumchadianensis,M .gracilentum ,丝状蓝绿藻Siphonophycusseptatum ,S .robustum ,S .tpicum ,S .kestron ,S .soldium ,Oscillatoriopsissp .和Salomenunavutensis,以及可能的多细胞藻类。

New microfossils are reported from the late Neoproterozoic Doushantuo Formation at Chaoyang Phosphorite Deposit in Jiangxi Province, South China. During the Doushantuo period, the Chaoyang area lies paleogeographically in a subtidal environment above fair weather storm wave base, just between Poyang Landmass to the north and Cathaysia Block to the south. The Doushantuo Formation at Chaoyang unconformably overlies the Nantuo tillites (of inferred Marinoan age), and conformably underlies the Dengying dolostones. It can be well correlated with succession of the Doushantuo Formation at Weng'an in Guizhou Province. The fossiliferous beds are in the upper part of the formation at Chaoyang. The microfossil assemblage includes acritarchs Asterocapsoides sp ., Megasphaera inornata, Meghystrichosphaeridium chadianensis, M. gracilentum, filamentous cyanobacteria Siphonophycus septatum, S. robustum, S. tpicum, S. kestron, S. soldium, Oscillatoriopsis sp. and Salome nunavutensis, and possible multicellular algae. The Chaoyang microfossil assemblage is quite different from the assemblages obtained from Weng'an in Guizhou and Baokang in Hubei in that it lacks convincing multicellular algae, which are very abundant in the latter two microfossil assemblages. Among the acritarchs found at Chaoyang Asterocapsoides sp., Megasphaera inornata and Meghystrichosphaeridium gracilentum also occur abundantly in the Doushantuo Formation in other areas of the Yangtze Platform, and Meghystrichosphaeridium chadianensis is a key element of the post-Marinoan glaciation Doushantuo/Pertatataka microflora (DPM) assemblage. Filamentous cyanobacteria found at Chaoyang, however, do not restrict to the Doushantuo Formation.