On the integration of Ordovician conodont and graptolite biostratigraphy: new examples from Gansu and Inner Mongolia in China

Abstract

Wang, Z.H., Bergström, S.M., Zhen, Y.Y., Chen, X. & Zhang, Y.D., 2013. On the integration of Ordovician conodont and graptolite biostratigraphy: New examples from Gansu and Inner Mongolia in China. Alcheringa 37, 510–528. ISSN 0311-5518.

Few Ordovician successions in the world contain both biostratigraphically highly diagnostic conodonts and graptolites permitting an integration between standard biozones based on these fossil groups. The Sandbian Guanzhuang section in the vicinity of Pingliang in the Gansu Province has an outstanding graptolite record through most of the Nemagraptus gracilis and Climacograptus bicornis graptolite biozones. Calcareous interbeds in the succession yield biostratigraphically important conodonts, including some species used for biozonations in Baltoscandia and the North American Midcontinent. Likewise, the middle–upper Darriwilian Dashimen section in the Wuhai region of Inner Mongolia hosts both diverse graptolites of the Pterograptus elegans, Didymograptus murchisoni and lowermost Nemagraptus gracilis biozones, and conodonts of Midcontinent and Baltoscandic types. The distribution patterns of these index fossil groups provide an unusual opportunity to closely correlate conodont and graptolite biozones in the middle to upper Darriwilian to Sandbian interval. For instance, the base of the C. bicornis Biozone is approximately coeval with the base of the Baltoscandic B. gerdae Subbiozone and a level near the middle of the North American P. aculeata Biozone.

Zhi-hao Wang [[email protected]] Xu Chen [[email protected]], and Yuan-dong Zhang [[email protected]], Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China; Stig M. Bergström [[email protected]], School of Earth Sciences, Division of Earth History, The Ohio State University, Columbus, OH 43210, USA; Yong Yi Zhen [[email protected]], Australian Museum, 6 College Street, Sydney NSW 2010, Australia.

关于奥陶纪牙行刺和笔石生物地层学的综合研究: 中国内蒙古鄂尔多斯盆地的新例子

奥陶纪地层很少同时含有具高度生物地层鉴定意义的牙行刺和笔石来对根据这些化石类群为基础的标准生物带之间进行对比。甘肃省平凉地区, Sandbian阶吴庄剖面中跨大部分Nemagraptus gracilis和Climacograptus bicornis笔石带的笔石记录非同一般。地层内钙质夹层中产生物地层意义重大的牙行刺, 包括一些在Battoscandia和北美中大陆用来划分生物带的种。同样, 内蒙Wuhai地区的中-上Darriwilian阶大石门剖面中有Pterograptus elegans生物带、 Didymograptus murchisoni 生物带和 Nemagraptus gracilis生物带最底部的多种笔石, 还含有中大陆型和Baltoscandic型牙行刺。这些标志型化石类群的分布模式提供了难得的机会, 来进行中-上Darriwilian阶至Sandbian阶牙行刺生物带和笔石生物带之间的严密对比。

Key words:

• conodonts
• graptolites
• biostratigraphy
• China
• Ordovician

Acknowledgements

The present research was supported by grants from National Nature Science Foundation of China (grants 41172034, 41290260 and 41221001). SMB gratefully acknowledges support from the Academia Sinica in Nanjing that made it possible for him to visit China in February–March, 2012. We also thank the journal reviewers John E. Repetski and Stephen A. Leslie for valuable comments on the manuscript. This paper is a contribution to IGCP Project 591 (‘The Early to Middle Paleozoic revolution’).