Geol. Mag.: page 1 of 22 c Cambridge University Press 2015 1 doi:10.1017/S0016756815000333 Archaeocyathan zonation of the Yangtze Platform: Implications for regional and global correlation of lower Cambrian stages ∗ AIHUA YANG †,MAOYANZHU‡, ANDREY YU ZHURAVLEV§, KEXING YUAN¶, JUNMING ZHANG‡ &YAQIANCHEN¶ ∗ State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, 163 Xianlindadao Ave., Nanjing 210046, China ‡State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Nanjing 210008, China §Department of Biological Evolution, Faculty of Biology, Moscow State University named after M.V.Lomonosov, Moscow, GSP-1, 119991, Russia ¶Kunming Prospecting Design Institute of China Nonferrous Metals Industry, Kunming 650051, China (Received 22 December 2014; accepted 1 May 2015) Abstract – Detailed analysis of the distribution of archaeocyaths in five lower Cambrian sections in South China has resulted in the erection of four new archaeocyathan zones and one new archaeocyathan bed. Listed in order of ascending age, these are: the Dailycyathus xiuqiensis Zone; the Dictyocyathus shaanxiensis Zone; the Spirillicyathus duplex Range Zone; the Sibirecyathus meitanensis Range Zone; and the Archaeocyathus yanjiaoensis beds. These new subdivisions permit a correlation of lower Cam- brian strata both within the area of the Yangtze Platform (South China) as well as between this region and Siberia, Australia, Western Europe and North America. Within the YangtzePlatform area, archaeo- cyaths of the Dailycyathus xiuqiensis and Dictyocyathus shaanxiensis zones co-occur with trilobites of the middle and upper Eoredlichia Trilobite Zone of the Qiongzhusian Stage. The Spirillicyathus duplex and the Sibirecyathus meitanensis Range Zone correspond to the Malungia, Yiliangella–Yunnanaspis and Drepanuroides Trilobite zones of the basal and middle Canglangpuan Stage, respectively. Finally, the Archaeocyathus yanjiaoensis beds belong to the Palaeolenus fengyangensis Trilobite Zone of the upper Canglangpuan Stage. Global correlations based on archaeocyath assemblage zones suggest that: (1) the middle–upper Qiongzhusian of South China correlates with the middle Atdabanian Stage of the Siberian Platform, the Warriootacyathus wilkawillinensis Archaeocyath Zone in South Australia, the middle Issendalenian Stage of Morocco and the lower Ovetian Stage in Spain; (2) the lower- most Canglangpuan Stage of South China correlates with the uppermost Atdabanian of the Siberian Platform, the Spirillicyathus tenuis – Jugalicyathus tardus archaeocyath zones in South Australia, the uppermost Issendalenian – lower Banian stages of Morocco, the middle Ovetian Stage of Spain and the middle Montezuman Stage of North America; (3) the middle Canglangpuan Stage approximates the lowermost Botoman Stage of the Siberian Platform, middle Banian Stage of Morocco, the uppermost Ovetian – lowermost Marianian stages of Spain and the upper Montezuman Stage of North America; (4) the uppermost Canglangpuan Stage is equivalent of the middle Toyonian Stage of the Siberian Platform, Archaeocyathus abacus beds in Australia, the middle Bilbilian Stage in Spain and the middle Dyeran Stage (Bolbolenellus euryparia Trilobite Zone) in North America. Keywords: lower Cambrian, archaeocyaths, biostratigraphy, South China. 1. Introduction International Working groups on the lower Cambrian stages and series have concentrated on creating reliable The International Subcommission on Cambrian Strati- datum planes in order to establish global boundary graphy has been working towards the development of stratotype sections and points (GSSPs) for these units. globally recognizable subdivisions of the Cambrian Siberia and South China are two particularly important System for nearly three decades. A particularly import- regions yielding abundant and diverse archaeocyath, ant step has been the adoption of a chronostratigraphic trilobite and small shelly fossil (SSF) faunas (Zhu, framework consisting of four series and ten stages Babcock & Peng, 2006; Zhu et al. 2007; Rozanov et al. (Babcock et al. 2005; Peng, Babcock & Cooper, 2012). 2008). Among these, archaeocyaths are of particular Despite these developments there are as yet no formal interest and utility for global correlations due to rapid subdivisions of the former Lower Cambrian, and global species turnover, high diversity and global distribution. chronstratigraphic subdivisions and correlations of Although a number of global correlation charts based lower Cambrian (Terreneuvian Series and Series on archaeocyaths with references to trilobites and SSFs 2) strata continue to be problematic. Recently, the have been proposed (Debrenne, Rozanov & Zhuravlev, 1990; Zhuravlev, 1995; Zhuravlev & Riding, 2001), †Author for correspondence: [email protected] these charts are considered by some to be problematic http://journals.cambridge.org Downloaded: 12 Nov 2015 IP address: 218.94.142.98 2 A. YANG AND OTHERS due to potential archaeocyath taxonomic inconsist- Zhang, 1977, 1978, 1980, 1982, 1983; Zhang & Yuan, encies, a high level of regional endemicity, and a 1984, 1985; Debrenne & Jiang, 1989; Belyaeva & possible dependence on substrate control (microfacies) Yuan, 1995; Yang & Yuan, 2012; Tables 1 and 2). Yuan (e.g. Geyer & Shergold, 2000; Landing et al. 2013). & Zhang (1980, 1981, 1982) and Zhang (1989)recog- However, such criticism might be equally applied to nized four successive archaeocyathan assemblages in any early Cambrian taxa (e.g. trilobites; Pegel’, 2000; central and southwestern areas of South China. Based in Álvaro et al. 2003) while archaeocyath systematics part on the archaeocyathan fossil record in the Fucheng are sophisticated and well documented (Debrenne, section, Yuan et al.(2001) established the Qiongzhus- Zhuravlev & Kruse, 2002, 2015). ian, Canglangpuan and Tianheban assemblages. How- The first high-resolution biostratigraphic scale using ever, archaeocyath taxonomy used by these authors is archaeocyaths was established on the Siberian Plat- now in need of revision, and no biozones have yet form where the Tommotian, Atdabanian, Botoman and been proposed. Consequently, the evolutionary history Toyonian stages and their zonation were partly or en- of Chinese archaeocyaths as well as their potential for tirely developed on the succession of archaeocyath as- global correlation is not well understood. semblages (Zhuravleva, 1960; Rozanov et al. 1969; The aim of the present study is to develop a high- Zhuravleva, Korshunov & Rozanov, 1969; Rozanov & resolution archaeocyath zonation based on recent taxo- Sokolov, 1984). Local archaeocyathan zones are estab- nomic revisions of previously described material and lished in the Altay Sayan Foldbelt of southern Siberia on the examination of new specimens (A. H. Yang, un- and the Russian Far East for the Atdabanian, Botoman pub. Ph.D. thesis, CAS, Nanjing, 2005; Yang & Yuan, and Toyonian stages where the most continuous Boto- 2012), allowing the application of these data to a reli- man and Toyonian archaeocyath fossil record exists able global correlation. (Repina et al. 1964; Zhuravleva et al. 1967; Borod- ina et al. 1973; Okuneva & Repina, 1973; Belyaeva 2. Materials and methods et al. 1975; Osadchaya et al. 1979; Osadchaya, 1986; Belyaeva, 1988; Astashkin et al. 1995). Subsequently, Five lower Cambrian sections on the Yangtze Plat- lower Cambrian archaeocyathan zonations were pro- form are selected and analysed in detail, namely: (1) posed for Spain (Perejón, 1984, 1994; Perejón & Fucheng near Nanzhen, Shaanxi Province; (2) Xinchao Moreno-Eiris, 2006), Canada, Greenland, Mexico and in Tongjiang County, Sichuan Province; (3) Shilixi near the United States (Debrenne & Peel, 1986; Zhuravlev in Meitan, Guizhou Province; (4) Yankong near Jinsha, Voronova et al. 1987; Debrenne, Gandin & Rowland, Guizhou Province; and (5) Wangjiaping near Yichang, 1989; Mansy, Debrenne & Zhuravlev, 1993; McMe- Hubei Province (Fig. 1). These sections are the refer- namin, Debrenne & Zhuravlev, 2000), South Australia ence sections for the lower Cambrian Qiongzhusian and (Gravestock, 1984; Zhuravlev & Gravestock, 1994; Canglangpuan stages in China, which are approximate Gravestock & Shergold, 2001), Morocco (Debrenne equivalents of stages 3 and 4 of the current International & Debrenne, 1995) and Mongolia (Zhuravlev, 1998). Chronostratigraphic Chart (Peng, Babcock & Cooper, These archaeocyathan zonations encompass the prin- 2012). cipal regions of archaeocyathan distribution and each Most of the 1400 archaeocyath-containing samples regional zonation works well – at a species level of under study were collected during field seasons of 1990, precision – within the former Cambrian palaeocontin- 2002 and 2003 from these sections. Of these, over 500 ents and adjacent terrane complexes, namely Siberia samples were collected from the Xiannudong Forma- (Siberian Platform and Kolyma Basin of Russia), the tion (Fucheng and Xinchao sections), 400 samples from Ural-Mongolian complex of terranes (the Urals, Altay the Mingxinsi Formation (Shilixi and Yankong sec- Sayan Foldbelt, Transbaikalia, Russian Far East, Kaza- tions) and 200 samples from the Tianheban Formation khstan, Kirgizia, Uzbekistan, Tajikistan and Mongolia), (Wangjiaping section). A preliminary analysis of some Laurentia (Canada, Greenland, Mexico and the United of these samples has been conducted by Yuan et al. States), Western Gondwana (Spain, France, Sardinia,