北京平谷中元古界高于庄组藻类微化石

ALGAL MICROFOSSILS OF THE MIDDLE PROTEROZOIC GAOYUZHUANG FORMATION IN PINGGU COUNTY,BEIJING

北京平谷中元古界高于庄组产丰富的藻类微化石,共6属7种,其中两新种:Archaeoellipsoides elongatus sp. nov.和Oscillatoriopsis regularis ps. nov.有关藻类微化石的系统报道在该区尚属首次,本文资料既丰富了中元古界古生物学内容,亦填补了该区藻类微化石研究的空白。

Algal microfossils have been found in black chert nodules of the middle Pro-terozoic Gaoyuzhuang Formation in the Pinggu area, Bei jing. All specimens in thinsections were studied under the microscope. This microfossil assemblage contains six genera, seven species, one indetermi-nate species and two unnamed forms. Most or all of the taxa described here mayhave cyanophytic affinity, with the dominance of filamentous forms over coccoids. The present assemblage is comparable to both the fossils from the middle Pro-terozoic Dismal Lakes Group of Canada and to those from the Wumishan Forma-tion of the Jixian System in the Ming Tombs, Beijing, China. The following new taxa are described: Cenus Archaeoellipsoides Horodyski & Donaldson, 1980 Type species: Archaeoellipsoides grandis Horodyski & Donaldson, 1980;p. 154,fig. 16, A, B-H. Archaeoellipsoides elongatus sp. nov. (pl. Ⅰ-10) Diagnosis: Plant bodies are large--sized and ellipsoidal, sometimes slightlycurved, solitary, rounded ends, singlelayered, with a smooth or coarse surface.51.5μm long, 6.2μm wide, 8.3 times as long as wide. Comparison: The new species has a relatively larger ratio of length/width;thus it differs from the others of this genus described before. Genus Oscillatoriopsis (Schopf) Mindelson & Schopf, 1982Type species: Oscillatoriopsis obtusa Schopf, 1968Oscillatoriopsis regularis sp. nov. (Pl. Ⅰ-1, 7, Pl. 11--18) Diagnosis: Multicellular trichomes are uniseriate, unbranched, straight, slightlyconstricts at septa, consist of 20--25 cells. Cells are depressed disc-shaped, contain-ing irregular dark organic matter, 11.5 μm long, 38μm wide. The ended cells arehalf--spheroidal. Comparison: The new species differs from the known species of the genus bythe whole ended cells and distinctly short trichomes.