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GFF Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/sgff20 Comments on some important issues concerning the establishment of a GSSP for Cambrian Stage 5 Yuanlong Zhaoa, Jinliang Yuanb, Qingjun Guoc, Jin Penga, Leiming Yinb, Xinglian Yanga, Chunjiang Wangd & Haijing Suna a College of Resource and Environment Engineering of University, 550025, ; b Nanjing Institute of Geology and Palaeontology, The Chinese Academy of Sciences, Nanjing 210008, China c Institute of Geographic Sciences and Natural Resources Research, Center for Environmental Remediation, Chinese Academy of Sciences, Beijing 100101, China d State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China Published online: 28 Feb 2014.

To cite this article: Yuanlong Zhao, Jinliang Yuan, Qingjun Guo, Jin Peng, Leiming Yin, Xinglian Yang, Chunjiang Wang & Haijing Sun (2014) Comments on some important issues concerning the establishment of a GSSP for Cambrian Stage 5, GFF, 136:1, 333-336, DOI: 10.1080/11035897.2014.884629 To link to this article: http://dx.doi.org/10.1080/11035897.2014.884629

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Comments on some important issues concerning the establishment of a GSSP for Cambrian Stage 5

YUANLONG ZHAO1, JINLIANG YUAN2, QINGJUN GUO3, JIN PENG1, LEIMING YIN2, XINGLIAN YANG1, CHUNJIANG WANG4 and HAIJING SUN1

Zhao, Y., Yuan, J., Guo, Q., Peng, J., Yin, L., Yang, X., Wang, C. & Sun, H., 2014: Comments on some important issues concerning the establishment of a GSSP for Cambrian Stage 5. GFF, Vol. 136 (Pt. 1, March), pp. 333–336. q Geologiska Fo¨reningen. doi: http://dx.doi.org/10.1080/11035897.2014.884629. Abstract: In order to help facilitate stratigraphic correlation between south China and Siberia, trilobite zones of Guizhou, China, and the Molodo River area, Siberia, need to be better coordinated. The Wuliu- Zengjiayan section is a strong candidate for the Global Standard Stratotype Section and Point for Cambrian Stage 5, and the Molodo River section provides important supplemental information that helps expand the precision of correlation on a global scale. The Kaili Formation in the Wuliu-Zengjiayan section contains three trilobite zones over an interval of 214.20 m. We propose that the Ovatoryctocara granulata Zone, as used in Siberia, replace the Ovatoryctocara Zone. Equivalent strata in Guizhou extend more than 150 m stratigraphically, from the Protoryctocephalus wuxunensis Zone to the Bathynotus kueichouensis–O. cf. O. granulata Assemblage Zone. We also propose that the traditional Kounamkites Zone be supplemented or replaced by the Oryctocephalus reticulatus Zone, which outside Siberia contains Oryctocephalus indicus. Keywords: Oryctocephalus indicus; Ovatoryctocara granulata; Cambrian Stage 5; GSSP; China; Siberia.

1College of Resource and Environment Engineering of Guizhou University, Guiyang 550025, China; [email protected] 2Nanjing Institute of Geology and Palaeontology, The Chinese Academy of Sciences, Nanjing 210008, China 3Institute of Geographic Sciences and Natural Resources Research, Center for Environmental Remediation, Chinese Academy of Sciences, Beijing 100101, China 4State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China Manuscript received 9 January 2014. Revised manuscript accepted 14 January 2014. Downloaded by [Jin Peng] at 08:59 12 June 2014

Introduction The first appearance datum (FAD) of Oryctocephalus indicus Some important factors or points of contention affecting the was originally proposed to mark the base of Cambrian Stage 5 decision about establishment of the GSSP for Stage 5 are and was accepted as a potential boundary horizon by the summarized as follows. International Subcommission on Cambrian Stratigraphy in 2005 (Babcock et al. 2005). More than 10 years have passed since the Working Group on Stage 5 was established (Geyer & Shergold Geographic distribution of potential FADs for 2000), and it has been 11 years since Fletcher (2003) first Stage 5 proposed the FAD of Ovatoryctocara granulata as another O. indicus was first described from the Himalayan region (Fig. 1, potential boundary marker of the Cambrian Stage 5. This No. 5) and has since been reported from Korea, south China (Fig. proposal was supported by Peng et al. (2006). Several field 1, Nos 1 and 2), Greenland (Fig. 1, No. 4), the United States (Fig. excursions have been organized to explore these and other 1, Nos 6 and 7) and Siberia (Fig. 1, No. 2; Zhao et al. 2012a). potential boundary levels, resulting in the delayed establishment Oryctocephalus reticulatus from Siberia can be distinguished of a GSSP for Cambrian Stage 5, as the issues regarding Stage 5 from O. indicus mainly by the undeveloped second and third pairs have been carefully considered by specialists. Two potential of transglabellar furrows (Shabanov et al. 2008). However, many boundary horizons and sections are the leading contenders under specimens of O. reticulatus from the Molodo River show poorly consideration: (1) the FAD O. indicus level in the Wuliu- developed second and third transglabellar furrows. The poorly Zengjiayan section, Guizhou, China and (2) the FAD developed transglabellar furrows may have resulted from Ovatoryctocara granulate level in the Molodo section, Siberia compaction in sediment, which opens the possibility that some (Yakutia), Russia. specimens of O. reticulatus could be reassigned to O. indicus.In 334 Zhao et al.: Comments on GSSP for Cambrian Stage 5 GFF 136 (2014)

Fig. 1. O. indicus (Reed, 1910) from south China, Siberia, Greenland, Himalayan region of India and North America. (1) Dorsal exoskeleton, GTB- 26-1-211, Wuliu-Zengjiayan section of the Kaili Formation, Balang, , Guizhou, China; (2) cranidium, HS-72-3, from base of the Tianpeng Formation of Mengzi County, Yunnan Province (Luo et al. 2009); (3) dorsal exoskeleton, with distinct transglabellar furrows in cranidium, from the Kounamkites Zone of the Kuonamka Formation, Molodo River section Siberia, previously referred to O. reticulatus Lermontova, 1940 by Shabanov et al. (2008, pl. 11, fig. 1); (4) cranidium previously referred to O. cf. indicus by Geyer & Peel (2011, fig. 19,A, Downloaded by [Jin Peng] at 08:59 12 June 2014 MGUH 29403 from GGU collection 482335); (5) cranidium, from Himalaya of India (see Jell & Hughes 1997); (6 and 7) from the Plagiura Zone, California: (6) cranidium, internal mold, USNM 4108055; (7) internal mold of thorax with pygidium, USNM 488757 (see Sundberg & McCollum 1997, figs. 9-4, 10); scale bar is 1 mm, except for image 2, which is 2 mm.

addition, the poorly preserved specimen assigned to Cheiruroides City (Zhao et al. 2012a). The species is also found at arcticus Tchernysheva, 1962 from the Oryctocara Zone the base of the Tianpeng Formation, which was deposited in a (Egorova et al. 1976, p. 97, pl. 43, fig. 14) has three pairs of shallow-water platform facies, in Mengzi County, Yunnan distinct transglabellar furrows, and it too could possibly be Province (Luo et al. 2009). reassigned to O. indicus. Some specialists have argued about whether O. reticulatus is a junior synonym of O. indicus (Korovnikov 2001, 2006; Zhao et al. 2001, 2007; Fletcher 2007; Candidate sections for the GSSP of Cambrian Yuan et al. 2011). However, we have found specimens in the Stage 5 Wuliu-Zengjiayan section of China that agree well with The Wuliu-Zengjiayan section through the Kaili Formation, in assignment to O. reticulatus (Zhao et al. 2012a), and for that Guizhou, China, is well exposed without significant tectonic or reason, we prefer to keep separate names for the two forms. metamorphic alteration. The section has been well studied, and Recently, some new localities yielding O. indicus have been more than 48 articles published about it (Zhao et al. 2012a). In recognized in south China. Most are in the Kaili Formation of this section, detailed trilobite studies have been conducted, and Guizhou Province. They include Sanwan section, Nangao Town in it the O. indicus Zone, with 91 m of strata, has been (Zhao et al. 2012b); Pingzhai section, Pingzhai Village, established and updated. Studies on acritarchs (Yin et al. 2010), Town, ; Zhuping section, Zhuping Village, sequence stratigraphy, carbon isotopes, sulfur isotopes (Guo et Zhengyuan County; Jianshan section, Chuandong Village al. 2013), rare metals and biomarkers indicate that the level Gedong Town, Jianhe County; and Wangjiayuan section, where we encounter the FAD of O. indicus approximates a GFF 136 (2014) Zhao et al.: Comments on GSSP for Cambrian Stage 5 335

Fig. 2. Correlation chart of the Cambrian Series 2–Series 3 boundary interval and ranges of selected trilobites (information from McCollum & Sundberg 2007; Zhao et al. 2007; Geyer & Peel 2011; Gozalo et al. 2011; Sundberg et al. 2011; Yuan et al. 2011).

turning point in Cambrian metazoan evolution. It is the point at O. reticulatus (Kounamkites) zones. These correspond to the which Redlichia disappears from the fossil record. This interval Protoryctcephalus wuxunaspis Zone of the Tsinghsutung also contains the famous Kaili Lagersta¨tte. Below the O. indicus Formation, and the B. kueichouensis–Ovatorytocara cf. O. Zone is the Bathynotus kueichouensis–O. cf. granulata granulata, O. indicus and Peronospis taijiangensis zones of the Assemblage Zone. overlying Kaili Formation in the Wuliu-Zengjiayan section (Fig. Similar to the Wuliu-Zengjiayan section, the Molodo River 2). Important fossils in the O. reticulatus (Kounamkites) Zone in section is also well exposed and lacks significant tectonic the Molodo River section include Kootenia multiformis, disturbance. Studies on trilobites, biomarkers and carbon K. rotundatus, O. reticulatus, O. reynoldisformis, O. vicinus, isotopes have been carried out (Shabanov et al. 2008). However, Pagetia ferox and Peronopsis recta. In the O. granulata Zone the trilobite biostratigraphy needs some updating to help assure occur O. granulata, O. ovata, C. arcticus, Oryctocephaalops better agreement with global zonation. O. reticulatus is very frischefeldi, Paradoxides eopinus and other trilobites (Shabanov similar to O. indicus and some specimens may indeed belong to et al. 2008). Bathynotus, the significant marker for the top of the O. indicus. Kounamkites is an endemic ptychopariid genus and Cambrian Series 2 (Peng et al. 2009) is present in Siberia and cannot be used for global correlation. We suggest either widely distributed globally. It is not known from the Molodo renaming the Kounamkites Zone as the O. reticulatus Zone, or River section but is associated with P. eopinus in the Lower- recognizing two separate zones based on trilobites having Imbak-219 well of the western Siberia Platform (Goryaeva et al. different paleoecologies and biofacies distributions, similar to 2012). This suggests that the appearance of P. eopinus correlates Downloaded by [Jin Peng] at 08:59 12 June 2014 the way separate trilobite zonations are recognized in Laurentia with the lower part of the range of Bathynotus. (e.g. Robison 1976; Babcock et al. 2011; Robison & Babcock 2011). A zonation based on oryctocephalids would allow easy correlation to global standards, whereas a zonation based on more endemic ptychopariids or other polymerids would facilitate correlation within Siberia. Ovatoryctocara occurs in Sections in the Mediterranean region the O. reticulatus Zone and ranges up into the lower portion of Sections through the Stage 4–Stage 5 interval in the the Kounamkites Zone (Shabanov et al. 2008). Recognition of Mediterranean region are dominated by endemic trilobites. In separate oryctocephalid and ptychopariid zones would separate addition, this interval in Western Gondwana shows numerous important zonal tools and simplify discussions about the ranges barren stratigraphic intervals and unconformities (A´ lvaro et al. of Kounamites and Ovatoryctocara, among other trilobites, in 2003). Together, these factors render correlation of Mediterra- the Molodo River section. Any new zonal names that may be nean sections with other regions challenging (Geyer & Peel proposed should be based on species rather than genera. 2011;Ga´mez Vintaned et al. 2011; Gozalo et al. 2011). Comparison with the Siberian section allows an approximate Global correlation of the Cambrian Stage 4– correlation of the Stage 4–Stage 5 boundary in the Mediterranean region with south China. Redlichia and Stage 5 boundary interval based on the Paradoxides are widely distributed in these regions. In south Wuliu-Zengjiayan section (south China) China, Paradoxides appears in the O. granulata (Ovatorycto- cara) Zone, which corresponds to Protoryctocephalus wux- Molodo River section, Siberia unaspis Zone in the Tsinghsutung Formation and to the base of The middle part of the Kuonamka Formation in the Molodo the B. kueichouensis–Ovatoryctocara cf. O. granulata Assem- River section embraces the O. granulata (Ovatorytocara) and blage Zone of the Wuliu-Zengjiayan section. 336 Zhao et al.: Comments on GSSP for Cambrian Stage 5 GFF 136 (2014)

Sections in other regions of the world Geyer, G. & Peel, S.J., 2011: The Henson Gletscher Formation, North Grenland, and its bearing on the global Cambrian series boundary. Bulletin of Geoscince Strata in the Wuliu-Zengjiayan section can be correlated with 86, 466–534. other strata containing O. indicus from North America, Geyer, G. & Shergold, J., 2000: The quest for internationally recognized divisions of Cambrian time. Episodes 23, 188–195. Greenland, the Himalaya and Korea. The Kaili Formation Goryaeva, I.E., Pegel, T.V., Shabanov, Y.Y. & Bushuev, E.V., 2012: New data yields many other widespread trilobite genera including on stratigraphic range of trilobite Bathynotus genus in Cambrian of Siberia Peronopsis, Pagetia, Burlingia, Euarthricocephalus, Pianaspis, Platform. Journal of Guizhou University 29 (Supplement 1), 164. Gozalo, R., Bautista, J., Martorell, C., Esteve, J. & Lin˜a´n, E., 2011: Correlation Olenoides, Bathynotus, Ovatorytocara, Protoryctocephalus and between the base of Drumian Stage and the base of middle Caesaraugustan Oryctocephalops, all of which provide secondary information Stage in the Iberian Chains (NE Spain). Bulletin of Geosciences 86 (3), for correlation (Fig. 2). The O. indicus horizon also has the 545–554. Guo, Q., Strauss, H., Zhao, Y., Yang, X., Peng, J., Yang, Y. & Deng, Y. 2013: advantage of coming close to the LAD redlichiid/LAD Reconstructing marine redox conditions for the transition between Cambrian olenellines horizon (Fig. 2). Series 2 and Cambrian Series 3, Kaili area, Yangtze Platform: Evidence from biogenic sulfur and degree of pyritization. Palaeogeography, Palaeoclimatol- ogy, Palaeoecology, http://dx.doi.org/10.1016/j.palaeo.2013.10.003. Jell, P.A. & Hughes, N.C., 1997: Himalayan Cambrian trilobites. Special Paper Final comments in Paleontology 58, 1–113. Korovnikov, I.V., 2001: Lower and Middle Cambrian boundary and trilobite If the Wuliu-Zengjiayan section were selected as the Global from northeast Siberia platform. Palaeoworld 13, 270–273. Standard Stratotype Section and Point for Cambrian Stage 5, Korovnikov, I.V., 2006: Lower and Middle Cambrian boundary in open shelf then the Molodo River section would provide a good facies of Siberian platform. Palaeoworld 15, 424–430. Luo, H.L., Hu, S.X., Hou, S.G., Cao, H.G., Zhan, D.Q. & Li, W.H., 2009: supplemental section. The section is condensed, containing six Cambrian Stratigraphy and Trilobites from Southeastern Yunnan, China. trilobite zones in the Kuonamka Formation over an interval of Cambrian stratigraphy and trilobites from Southeastern Yunnan, China, only 44.4 m. O. granulata ranges through a 6.7-m interval of Kunming. 250 pp. (in Chinese with English abstract). McCollum, L.B. & Sundberg, F.A., 2007: Cambrian trilobite biozonation of the strata; and the Oryctcephalus reticulatus Zone is a 12.4-m Laurentia Delamaran Stage in the southern Great Basin, U.S.A.: implications interval of strata that contains diverse trilobite species, including for global correlations and defining a Series 3 global boundary stratotype. Memoirs of Association of Australasian Palaeontology 34, 147–156. some that occur in the P. eopinus Zone of the Mediterranean Peng, S.C., Babcock, L.E., Geyer, G. & Moczydłowska, M., 2006: Nomenclature region. The Molodo River section provides important infor- of Cambrian epochs and series based on GSSPs – comments on an alternative mation for the global correlation of the Stage 4–Stage 5 interval, proposal by Rowland and Hicks. Episodes 29, 130–132. Peng, J., Zhao, Y.L., Yuan, J.L., Yao, L. & Yang, H., 2009: Bathynotus—a key especially in reference to P. eopinus, O. granulata, O. trilobite taxon for global stratigraphic boundary correlation between Cambrian reticulatus, P. recta and other trilobite species from this section Series 2 and Series 3. Progress in Natural Science 19, 99–105. (see Fig. 2). Robison, R.A., 1976: Middle Cambrian trilobite biostratigraphy of the Great Basin. Brigham Young University Geology Studies 23 (2), 93–109. Acknowledgements – The authors thank Dr F.A. Sundberg for revision in English and Robison, R.A. & Babcock, L.E., 2011: Systematics, paleobiology, and comment on the manuscript, and Profs T.P. Fletcher, L.E. Babcock, I.V. Korovnikov, S.C. taphonomy of some exceptionally preserved trilobites from Cambrian Peng and P.D. Kruse for providing significant information for the manuscript. The authors Lagersta¨tten of Utah. Paleontological Contributions 5, 1–47; http://hdl. also thank two reviewers for their valuable comments and helpful suggestions for revision. handle.net/1808/8543 Paleontologists from the United States, F.A. Sundberg, L.B. McCollum, L.E. Babcock, Lin Shabanov, Y.Y., Korovnikov, I.V., Pereladov, V.S. & Fefelov, A.F., 2008: Jih-Pai and R. R. Gaines have cooperated with us for a long-term study of the boundary interval between Stage 4 and 5 of the Wuliu-Zengjiayan section (south China), and Excursion 1a. The traditional Lower–Middle Cambrian boundary in the acknowledge their important contributions. This research is also a large group achievement. Kuonamka Formation of the Molodo River section (the southeastern slope of This research was supported partly by grants from the Major state Basic Research the Olenek Uplift of the Siberian Platform) proposed as a candidate for GSSP Development Program of China (973 program) (No. 2013CB835002), the National Science of the lower boundary of the Middle Cambrian and its basal (Molodian) stage, Foundation of China (NSFC, Nos. 41172005, 41330101), the Key Project of International defined by the FAD of Ovatoryctocara granulata. The Cambrian System of Cooperation of Guizhou Science and Technology Department (Gui. No. 2010-7001), the the Siberian Platform. Part 2: North-East of the Siberian Platform, XIII Science Technology and Education Talent from Government of Guizhou Province (Gui. International Field Conference of the Cambrian Stage Subdivision Working Sp.2011-37) and Fund of Stratigraphical Commission of China. Group, Moscow, Novosibirsk. Sundberg, F.A. & McCollum, L.B. 1997: Oryctocephalids (Corynexochida: Trilobita) of the Lower-Middle Cambrian Boundary Interval from California and Nevada. Journal of Palaeontology 71 (6), 1065–1090. Downloaded by [Jin Peng] at 08:59 12 June 2014 References Sundberg, L.A., Zhao, Y.L., Yuan, J.L. & Lin, J.P., 2011: Detailed trilobite A´ lvaro, J.J., Elicki, O., Geyer, G., Rushton, A.W.A. & Shergold, J.H., 2003: biostratigraphy across the proposed GSSP for Stage 5 (“Middle Cambrian” Palaeogeographical controls on the Cambrian trilobite immigration and boundary) at the Wuliu-Zengjiayan section, Guizhou, China. Bulletin of evolutionary patterns reported in the western Gondwana margin. Palaeogeo- Geoscience 86, 423–464. graphy, Palaeoclimatology, Palaeoecology 195, 5–35. Yin, L.M., Zhao, Y.L., Yang, R.D. & Peng, J., 2010: Restudy of Acritarchs from Babcock, L.E., Peng, S.C., Geyer, G. & Shergold, J.H., 2005: Changing the Early-Middle Cambrian Kaili Formation at Wuliu-Zengjiayan Section, perspectives on Cambrian chronostratigraphy and progress toward subdivision east Guizhou Province, China. Acta Palaeontolgica Sinica 49 (2), 164–173. of the Cambrian System. Geosciences Journal 9, 101–106. Yuan, J.L., Zhu, X.J., Lin, J.P. & Zhu, M.Y., 2011: Tentative correlation of Babcock, L.E., Robison, R.A. & Peng, S.C., 2011: Cambrian stage and series Cambrian Series 2 between South China and other continents. Bulletin of nomenclature of Laurentia and the developing global chronostratigraphic Geoscince 86, 397–404. scale. Museum of Northern Arizona Bulletin 67, 12–26. Zhao, Y.L., Peng, J., Yuan, J.L., Loren, E.B., Guo, Q.J., Yin, L.M., Yang, X.L., Egorova, L.I., Shabanov, Y.Y., Rozanov, A.Y., Savitsky, V.E., Tchernysheva, Tai, T.S., Wang, C.J., Lin, J.P., Robert, R.G., Sun, H.J. & Yang, Y.N., 2012a: N.E. & Shishkin, B.B., 1976: The Elanka and Kuonamka facies stratotype of Discussion of candidate stratotypes for the GSSP defining the conterminous the lower boundary of the Siberian Middle Cambrian. Sibirskiy nauchno- base of Cambrian provisional Series 3 and Stage 5. Journal of Guizhou issledovatelskiy institute geologii, geofiziki I mineralnogo syr’ya (SNIIG- University 29 (Supplement), 35–48. GIMS), Trudy 211, 1–167. (in Russian). Zhao, Y.L., Yang, Y.N., Peng, J., Yuan, J.L., Sun, H.J., Yan, X. & Zhang, P.X., Fletcher, T.P., 2003: Ovatoryctocara granulata: the key to a global Cambrian 2012b: The Kaili Formation and Kaili Biota at the Sanwan Section in Guizhou stage boundary and the correlation of the olenellid, redlichiid and paradoxidid Province, China and boundary between Cambrian Series 2/Series 3. Journal of realms. Palaeontology 70, 73–102. Guizhou University 29 (Supplement), 77–88. Fletcher, T.P., 2007: The base of Cambrian Series 3: the global significance of Zhao, Y.L., Yuan, J.L., Peng, S.C., Babcock, L.E., Peng, J., Lin, J.P., Guo, Q.-J. key oryctocephalid trilobite ranges in the Kaili Formation of South China. & Wang, Y.X., 2007: New data on the Wuliu-Zengjiayan section (Balang, Memoir of Association of Australasian Palaeontologists 33, 29–33. South China),GSSP candidate for the base of Cambrian Series 3. Memoirs of Ga´mez Vintaned, J.A., Zhuravlev, A.Yu., Bauluz, B., Bubı´as, I., Chirivella Association of Australasian Palaeontologist 33, 57–65. Martorell, J.B., Mayoral, E., Gursky, H.-J., Andre´s, J.A. & Lin˜a´n, E, 2011: Zhao, Y.L., Yuan, J.L., Zhu, L.J., Guo, Q.J., Yang, R.D., Yang, X.L. & Tai, T.S., Proposal of a reference section and point for the Cambrian Series 2–3 2001: An advance in the research of the Lower–Middle Cambrian boundary in boundary in the Mediterranean subprovince in Murero (NE Spain) and its South China and its propects. Jounal of Stratigraphy 25 (Supplement), international correlation. Geological Journal, doi:10. 1002/gj.1330. 383–390.