苏皖北部新元古代微生物化石

NEOPROTEROZOIC MICROFOSSILS FROM NORTHERN JIANGSU AND ANHUI

苏皖北部新元古代海相泥页岩、粉砂岩及燧石中富含微生物化石。其中 ,通过化学浸解法 ,从碎屑岩中获得14个形态属种的微生物化石 ;6个形态属种的蓝细菌化石呈三维立体状态保存在燧石切片中。浸解获得的泥页岩、粉砂岩相微生物化石 ,在刘老碑组中—上部的主要是片形和球形 :L aminarites antiquis-simus,L eiosphaeridia pelucida,Spumiosa alara及 Asperatopsophosphaera bavlinensis;在九里桥组、贾园组和赵圩组主要为多面形和球形 :Monilinema quadratucella及 Synsphaeridium sp.;而史家组、金山寨组和沟后组则有丰富的球形、片形、梭形和带形个体 :L eiosphaeridia hyperboreica,Trachysphaeridium simplex,Annulum difuminatum,N ucellosphaeridium asperatum,Tophoporata sp.,Symplassosphaeridium sp.,Macroptycha uniplicata及 Taenia-tum simplex。该微生物组合可与河北及天津蓟县的新元古界景儿峪组和下马岭组的相对比。虽然上述微生物化石的系统古生物学仍在研究中 ,但却为我们了解新元古代大冰期前夕近岸海相环境生物圈提供了有关浮游植物的信息。苏皖北部新元古代倪园组及九顶山组的燧石中 ,保存良好的微生物三维立体化石为丝形和球形蓝细菌遗留物 ,包括 Siphonophycus sp.。

Abundant microfossils were uncovered in marine Neoproterozoic shales, siltstones, and cherts in northern Jiangsu and Anhui provinces, East China. Microfossils in clastic rocks are extracted by maceration and 14 genera and species are identified. Coccoid and filamental cyanobacterial microfossils are three dimensionally well preserved in cherts and 6 taxa are recognized in petrographic thin sections. Macerated microfossils in the upper and middle parts of the Neoproterozoic Liulaobei Formation mainly are fragments with multilayers or monolayers and sphaeromorphs. They are Laminarites antiquissimus, Leiosphaeridia pelucida, Spumiosa alara , and Aspera topsophosphaera bavlinensis . Only two types, Monilinema quadratucella and Synsphaeridium sp., are collected from the Jiuliqiao, Jiayuan and Zhaowei formations, which are polyhedrical or spherical in shape. Abundant spherical and filamental microfossils are macerated from the clastic rocks of the Shijia, Jin shanzhai and Gouhou formations, including Leiosphae ridia hyperboreica, Trachysphaeridium simplex, Annulum difuminatum, Nucellosphaeridium asperatum, Tophoporata sp., Symplassosphaeridium sp., Macro ptycha uniplicata and Taeniatum simplex . This microfossil assemblage can be compared with those of the Neoproterozoic Jingeryu and Xiamaling formations in Jixian, Tianjin, and Hebei Province. Although the systematic paleontology of the above mentioned microfossils is still under investigation, they could provide us with phytoplanktonic data for understanding the biosphere of the coastal marine environment shortly before the Neoproterozoic glaciations. Well preserved three dimensional microfossils, including filamental and coccoid cyanobacteria, occur in the cherts of the Neoproterozoic Niyuan and Jiudingshan formations in northern Anhui and Jiangsu provinces. They are Siphonophycus sp., Eoentophysalis belcherensis, Eozygion grande, Tetraphycus conjionceum, Globophycus rugosum , and Caryosphae roides pristine . This cyanobacteria assemblage was probably benthic, and occurred in nonstromatolitic carbonate depositional environment.