Integrated Conodont Biostratigraphy and Carbon Chemostratigraphy of the Upper Ordovician Shiyanhe Formation at the Sigang Section, Neixiang, Henan, Central China
1 State Key Laboratory of Geobiology and Environmental Geology, China University of Geosciences, Beijing 100083, China; jxch@cugb.edu.cn, 410529674@qq.com;
2 Natural History Museum of Denmark, Geological Museum, Earth and Planetary System Science Section, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark; svends@snm.ku.dk.
1 Introduction
The Upper Ordovician Shiyanhe Formation, which occurs in Central China, represents the most continuous Katian carbonate deposition so far known in China. The 186-m-thick Shiyanhe Formation exposed at the Sigang section, Neixiang area, Henan, Central China (Fig. 1) has been investigated for conodonts and carbon isotopes (Fig. 2). Abundant conodonts obtained from the Formation allow recognition of a revised conodont biostratigraphic scheme (Jing et al., 2017).
2 Biostratigraphy
The Oulodus ulrichi, Oulodus robustus, Aphelognathus grandis and Aphelognathus divergens conodont biozones are introduced(Jing et al.,2017)and the conodont fauna and biozones of the Shiyanhe Formation are referred to the Katian Stage (Stage slices Ka2-Ka4) of the Upper Ordovician (Zhen et al., 2015). Regionally, the Shiyanhe Formation fauna is relatively similar to contemporaneous faunas from the Tarim terrane in western China (Wang & Zhou, 1998; Zhao et al., 2000; Wang & Qi, 2001; Jing et al., 2007) and from the southwestern margin of the North China Platform (An & Zheng, 1990; Zhen et al., 2016;Bergström & Ferretti, 2016). However, the faunal composition also shows a close affinity to the North American Midcontinent Province (Sweet, 1979) and the correlation to North America is clear (Sweet, 1984, 1988).
3 Carbon chemostratigraphy
The δ13C values of 111 limestone samples from the Shiyanhe Formation of the Sigang section document the presence of at least 3 positive excursions (Fig. 2), which can be correlated with the Fairview, Waynesville and Whitewater excursions that were previously found in North America (Bergström et al., 2010). This result further confirms that the Late Ordovician carbon isotope zonation established in North America has a continent-wide distribution and is a useful tool for improving long-distance correlations.
Figure 1 Simplified geology of location maps (A is modified after Zhang et al., 1996)
Acknowledgements This work was supported by the National Natural Science Foundation of China (No. 41502026), the State Key Laboratory of Biogeology and Environmental Geology, China (No. GBL21511), and the China Scholarship Council (No. 201506405017).
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