The Early–Middle Ordovician graptolite sequence of the Upper Yangtze region, South China

• Zhang Yuandong ^[1] ; Chen Xu ^[1]
  1. [1] State Key Laboratory of Palaeobiology and Stratigraphy (Nanjing Institute of Geology and Palaeontology, CAS), Nanjing
• Localización: Serie correlación geológica, ISSN-e 1666-9479, ISSN 1514-4186, Vol. 17, Nº. 1, 2003
• Idioma: inglés
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• Resumen

  • The Upper Yangtze region yields rich early to middle Ordovician graptolites of ‘Atlantic’ affinity. In this region, the Tremadoc strata are dominated by carbonates, in which graptolites are rare and difficult to be encountered, whereas the strata of post–Tremadoc to early Caradoc are dominated by graptolitic shales with intercalated limestones. Since the 1960’s, considerable work has been done to discover graptolites from a variety of localities (Lee and Chen, 1962; Zhang et al., 1964; Mu et al., 1979). Based on these collections, Mu et al. (1979) were able to propose a "standard" graptolite succession for the region, although there are diverse arguments about the taxonomy of the graptolites. Wang X.F. (1982) and Fu (in Lai et al., 1982) systematically discussed the sequence and its correlation.

    In recent years we, together with some of our colleagues from Nanjing Institute of Geology and Palaeontology, recollected some of these reference sections in the border area between Guizhou and Sichuan Provinces, including particularly two sections in Sichuan: the Shuanghe section in Changning (Figure1, Loc.7) and Nayangqing in Gulin (Loc.9), and four sections in northern Guizhou: the Honghuayuan section in Tongzi (Loc.14), the Shizipu (Gaoqiao) section in Zunyi (Loc.15), the Wulipo section in Meitan (Loc.16) and the Shatuodu section in Yanhe (Loc.12). Based on a study of the graptolite specimens from these sections, as well as a restudy of some of those (stored in NIGP and KUST) from other sections, a revised graptolite biozonation scheme for the Upper Yangtze region is proposed herein.