从塔北隆起奥陶纪钙藻化石探讨奥陶纪的古环境  

PALAEOENVIRONMENTAL ANALYSES OF ORDOVICIAN ROCKS IN THE NORTHERN UPLIFT OF TARIM BASIN IN TERMS OF CALCAREOUS ALGAE AND CYANOBACTERIA

作　　者：范嘉松[1] 吴亚生[1] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029

出　　处：《微体古生物学报》2004年第3期251-266,共16页Acta Micropalaeontologica Sinica

摘　　要：塔里木盆地塔北隆起轮南 4 6井、英买 1、2井奥陶纪石灰岩内含有大量的钙藻化石、蓝细菌以及疑难微体化石。这些钻井岩芯均在深达 5 0 0 0— 6 2 0 0 m的地下深部取得。钙藻主要为绿藻类的 Dasyporella,Vermiporella,Moniliporella以及 ?Plexa;红藻类的管孔藻类 Solenoporaceans;钙化蓝细菌则有 Girvanella,Botomaella,?Subti-floria等 ;疑难微体化石有 Bevocastria,N uia,Rothpletzella。这些钙藻生活于热带或亚热带正常盐度的浅海水内 ,其水深不到 2 0 m。世界各地的奥陶纪 Vermiporella均位于古赤道的两侧 ,这表明它们是在气候炎热、温暖海水中生活的一类海洋藻类。 Girvanella以藻灰结核和内碎屑最为常见 ,某些球粒可能代表 Girvanella破碎后形成的单管或小棒。塔里木盆地钙藻植物群相似于哈萨克斯坦、波罗的海周围地区以及北美同时代植物群 ,这表明这些钙藻和蓝细菌化石具有遍布于全球的性质。塔北隆起早、中奥陶世沉积属于典型的碳酸盐岩台地相沉积。到晚奥陶世时 ,碳酸盐岩沉积被浅水陆棚沉积所取代 ,以陆源碎屑岩为主 ,夹少量的碳酸盐岩。Abundant calcareous algae and cyanobacteria were found in the Ordovician limestone cores from three wells, LN-46, Yingmai-1 and Yingmai-2, in the northern uplift of the Tarim Basin. All of these fossils were collected from the depth of 5 000? ? 200m subsurface. Calcareous algae include green algae: Dasyporella, Vermiporella, Moniliporella and ?Plexa,and red algae Solenoporaceans. Calcified cyanobacteria contain Girvanella, Botomaella and ?Subtifloria. Microproblematica are Nuia, Bevocastria and Rothpletzella. These calcareous algae, calcified cyanobacteria and problematic microfossils lived only in shallow marine waters of normal salinity of tropical or subtropical areas, with depths of less than 20m.All of the Ordovician Vermiporella in the world were distributed on both sides of paleoequator, indicating that Vermiporella represents one kind of marine algae which lived in warm waters under hot and humid climate condition. Girvanella in the Ordovician deposits occurs usually as oncolites and intraclasts of silt-and sand-size; some pellets probably represent flagments of Girvanella, usually appearing as single tubes or small rods. The Tarim flora broadly resembles those from Kazakhstan, Baltica and North America, indicating the generally cosmopolitan nature of Ordovician calcareous algae and cyanobacteria. Early and Middle Ordovician deposits in the northern uplift of the Tarim Basin are regarded as of typical carbonate platform; but during Late Ordovician, these carbonate deposits were replaced by shallow water shelf deposits, in which terrigenous clastic deposits with minor carbonate intercalations predominate.

关 键 词：钙藻 蓝细菌 古环境 奥陶纪 塔里木盆地 新疆 化石 

分 类 号：Q913[天文地球—古生物学与地层学]