徐淮地区元古宙九顶山组燧石中微体生物化石新资料

我国徐淮地区元古宙九顶山组产出丰富的条带状和结核状燧石,其中保存了大量微体生物化石。本研究通过岩石切片法发现了呈三维立体状态保存的精美的丝状和球状蓝藻化石,鉴定出12属16种,即有丝状蓝藻6属10种(包含2个未定种):Siphonophycus septatum,S.robustum,S.typicum,S.kestron,Oscillatoriopsis ver-miformis,O.obtusa,Cephalophytarion grande,Salome sp.,Veteronostocale amoenum,Paleolyngbyasp.;球状蓝藻3属3种:Gloeodiniopsis suxianensis,Eoentophysalis cumulus,Nanococcus vulgaris;以及分类位置未定的3属3种(包含1个未定种):Myxococcoides minor,Leiosphaeridiasp.,Brachypleganon khandanum。其中Oscil-latoriopsis vermiformis,O.obtusa,Cephalophytarion grande,Salome sp.,Veteronostocale amoenum,Paleolyn-gbyasp.,Nanococcus vulgaris均为本地首次发现,弥补了以前在九顶山组中只找到Siphonophycus而未曾见Os-cillatoriopsis的缺憾,并对大量保存精美的Siphonophycus的来源问题给出了可能的解释。而大量无异形胞的Os-cillatoriopsis属化石的存在可能反映了当时的海底为缺氧环境。本次新发现丰富了九顶山组的微体生物化石资料,这些微体生物化石组合有可能成为元古宙洲际生物地层对比的依据。九顶山组碳酸岩台地沉积相中普遍发育的微体生物藻席、保存精美的高分异度的蓝藻化石以及并未在底栖环境中发现真核生物,均反映冰期前的浅海底栖生态系统还是由原核生物为主体的微体生物生态系统。

NEW DATA ON SILICIFIED PROTEROZOIC MICROFOSSILS FROM THE JIUDINGSHAN FORMATION OF JIANGSU AND NORTHERN ANHUI,CHINA

The Middle to Late Proterozoic Jiudingshan Formation of Jiangsu and northern Anhui provinces contains abundant laminar and nodular cherts that have revealed a diverse and well preserved microfossil assemblage in thin sections:The assemblage is dominated by 12 genera,represented by 16 species in all,among which are 6 genera-with 10 species-of filamentous forms and three genera and species of coccoidal ones.These 9 genera and 13 species are probably all cyanobacteria:Siphonophycus septatum,S.robustum,S.typicum,S.kestron,Oscillatoriopsis vermiformis,O.obtusa,Cephalophytarion grande,Salome sp.,Veteronostocale amoenum,Paleolyngbya sp.,Gloeodiniopsis suxianensis,Eoentophysalis cumulus and Nanococcus vulgaris.Another three genera and species are regarded here as incertae sedis:Myxococcoides minor,Leiosphaeridia sp.and Brachypleganon khandanum.The occurrences of Oscillatoriopsis vermiformis,O.obtusa,Cephalophytarion grande,Salome sp.,Veteronostocale amoenum,Paleolyngbya sp.and Nanococcus vulgaris are the first to be recorded from this region of China.The important mat-building elements Siphonophycus and Oscillatoriopsis always appeared to be associated together in the present study,supporting an interpretation that the two may be closely related.Previously only Siphonophycus has been found in this locality,without any associated Oscillatoriopsis.Palaeoecologically,the occurrence of a large number of Oscillatoriopsis filaments lacking heterocysts in the Jiudingshan Formation implies that environmental conditions were anaerobic.Oscillatoriopsis filaments lacking heterocysts in the Jiudingshan Formation imply that environmental conditions were anaerobic.This new discovery of microfossils from the Jiudingshan Formation is systematically significant in amplifying and extending our knowledge——providing a more complete understanding of Proterozoic microbial communites worldwide and also giving us a more complete understanding of their environments.It reveals that prokaryotic organisms clearly played the most important role in the microbial community of shallow benthic marine environments in this locality prior to the onset of the Neoproterozoic glaciation.