黔东、湘西元古代晚期锰矿沉积中的微体化石

应用电子显微镜技术和通常的孢粉浸渍方法,从黔东、湘西晚元古代冰期的锰矿层,收集到丰富的微体化石和有机残余物。参考同位素年龄测定数据,可以推测黔东、湘西两地锰矿沉积的年龄,大致为750 Ma。很特征的是,从两地的菱锰矿获得大量定形群体的微体化石——Sphaerocongragus(或Bavlinella)及其降解的变体。它们的生物和生物化学作用,结合锰本身不同途径的地球化学作用,在锰的循环中起重要影响。     

皖南变质岩中古生物化石及其大地构造意义

安徽省南部浅变质岩区以往称作元古宙上溪群并与板溪群对比,它的分布区被称作“江南古陆”。最近先后在这个地区的变质岩中找到古生代的疑源类化石Baltisphaeridium sp。以及腕足类Lingulacea fam. et gen indent.,同时在其北缘原划归震旦纪的地层中找到石炭纪的具环三缝孢为主的孢粉组合和锥石类(?)Conulariid(?)等,证明本区变质岩的相当一部分为古生代地层。同时也说明这里的构造格局和演化过程与以往所说很不相同。     

MICROFOSSILS FROM LATE PROTEROZOIC MANGANESE ORE DEPOSITS IN WESTERN HUNAN PROVINCE AND EASTERN GUIZHOU PROVINCE, SOUTH CHINA

Abundant microfossils and organic residuals have been discovered by SEM and normal palynological maceration from manganese ore beds intercalated in late Proterozoic glacial rock units in western Hunan Province and eastern Guizhou Province. Taking isotopic dating into consideration, the age of manganese ore deposits in both regions is suggested to be about 750 Ma. A distinct character is that a great quantity of colonial microfossil——Sphaerocongregus (or Bavlinella) and their degradational variants have been obtained from rhodochrosite. Their biological and biochemical functions, combined with the geochemical effect of manganese in different ways, may play an important role in the manganese cycle.     

The Fossils in Shangxi Group and Its Implication for Tectonics, Southern Anhui, China

The Shangxi Group is the local name in southern Anhui Province and it is believed to be the equivalence of the well-known Banxi Group in Hunan Province, southern China. So the area occupied by the Shangxi Group was regarded as a part of the "Jiangnan old land" of Presinian till it was challenged by the present authors years ago. After we postulated that there may be some strata of Palaeozoic Era in Shangxi Group, some microfossils and then macrofossils of Palaeozoic were found in some part of it. The macrof os-sils, Lingula sp. , Conulariid and the microfossils indicate that most units of the Shangxi Group are Palaeozoic strata. Based on the discovery of these fossils and the recognition of the tectonic-setting of the different tectono-petrologic units in the Shangxi Group, three different stratigraphic sequences (island-arc volcanics, back-arc sediments and the cover of passive margin of Yangtze Continental Plate) are established and the tectonic evolution of them is postulated in the present paper. Al