摘要
陕南紫阳、岚皋一带志留系发育,化石丰富,主要为笔石页岩相,局部夹介壳相灰岩薄层。由于本区处于秦岭褶皱系的北大巴山褶皱带,构造复杂,给地层古生物的研究带来了困难。笔者曾在本区及陕西平利、湖北竹溪等地进行工作,对五峡河组、白崖垭组和安坪梁组的时代有新的认识。
The late Early and Middle Silurian strata well exposed in Langao and Ziyang of Shaan-xi consist mainly of black, dark grey and light green shales, siltstones, fine sandstones and slate, which were named Wuxiahe Formation in 1963. This formation contains rich grapto-lites and is intercalated with limestones bearing abundant corals and brachiopods. These limestones were named Baiaiya Formation in 1963 and total 30-40m thick at Baiaiya, 20m at Wuxiahe and thin out toward the west. Graptolites Oktavites spiralis, Monograptus sp. were found from the shales and siltstones immediately above and below the limestones in the Baiaiya and Wuxiahe sections. Cyrtograptus centrifugus, C. lapworthi, C. sp..Monoclima-cis vomerina, Monograptus priodon, Oktavites spiralis, Stomatograptus grandis and Retiolites sp. were obtained from the light-dark grey shale above the limestones in Baiaiya. Distribution of these limestones and aspects of the graptolites in the shales above and below indicate that the name Baiaiya Formation should be abandoned and that these limestones are the intercalated layers and the local facies change of the Wuxiahe Formation. The lithology, litho-facies and metamorphoic grade of the Anpingliang Formation named by Ge Mei-yu in 1985 are the same as those of the Wuxiahe Formation. The only difference between them is in the genera and species of graptolites, those in the former formation being Middle Silurian elements and those in the latter formation being Early Silurian elements. Thus, the Anpingliang Formation is probably the upper part of the Wuxiahe Formation and its name should be abandoned too. The Wuxiahe Formation was deposited during the time from late Llandoverian to Wenlockian age and is not the only sediment of late Llandoverian or Wenlockian age.
出处
《地层学杂志》
CSCD
北大核心
1992年第4期316-319,共4页
Journal of Stratigraphy
