【摘要】 陕西渭北地区晚奥陶世裂陷成深水环境,构成北秦岭弧后盆地的一部分,接受了一套碳酸盐岩斜坡相沉积。在其下部地层首次分离出一个保存良好,属种丰富的放射虫化石组合Inanibigutta aff.inconstans-Syntagentactinia biocculosa组合,计有7科、14属、23种、4新种,以Inaniguttidae、Haplentactiniidae、Polyentactiniinae为特征,与哈萨克斯坦放射虫组合面貌一致,不存在澳洲和美洲的Kalimnasphaera等分子,就目前所知亚洲这一地区是全球奥陶纪放射虫分异度最高的地区,反映了北秦岭古海洋与古亚洲洋是相通的。更多还原

【Abstract】 The Weibei area is located on the north side of the Weihe River near the Qinling Mountains. During the early Palaeozoic it belonged to the North China carbonate platform, but at the beginning of the Late Ordovician, it subsided and developed into a deep-water basin merging into the North Qinling back-arc basin, where it received carbonate slope deposits of a total thickness of about 800 m, including thin -bedded limestones, cherts, tuff and brecciform limestone as well as slumped limestones. This set of strata, named the Zhaolaoyu Formation by Mei Zhichao et al. , yields radiolarians, graptolites and conodonts in its lower part. Graptolites and conodonts collected from the thin-bedded limestones indicate a Caradocian age. The well - preserved radiolarian Inanibigutta aff. inconstans-Syntagentactinia biocculosa assemblage produced in it is characterized by a high diversity with 7 families, 14 genera and 23 species, the dominance of Inanigutti-dae, Halpentactiniidae and Polyentactiniinae, and especially Inanigutta, Inanibigutta, and Polyentactinia, inadequacy of Entactiniinae and Palaeoscenidiidae existing dominantly in the Ordovician of Europe, America and Australia, in particular, and absence of the important element, Kalimnasphaera, of Australia and America. Therefore, the general feature of this assemblage is very similar to that of the Landeilo-Caradocian assemblage of Kazakhstan. As is known at present , Asia is the place rich in the most highly diverse Ordovician radiolarian fossils. These facts indicate that the ancient Qinling Ocean can have been related to the Palaeasia Ocean.更多还原