- Email: [email protected]
Comment on “Terreneuvian small shelly faunas of east Yunnan (South China) and their biostratigraphic implications” by B. Yang et al. [Palaeogeography, Palaeoclimatology, Palaeoecology 398 (2014) 28–58]
Comment on “Terreneuvian small shelly faunas of east Yunnan (South China) and their biostratigraphic implications” by B. Yang et al. [Palaeogeography, Palaeoclimatology, Palaeoecology 398 (2014) 28–58] Ed Landing, Gerd Geyer PII: DOI: Reference:
S0031-0182(16)30071-2 doi: 10.1016/j.palaeo.2016.04.016 PALAEO 7782
To appear in:
Palaeogeography, Palaeoclimatology, Palaeoecology
Received date: Revised date: Accepted date:
25 February 2016 29 March 2016 5 April 2016
Please cite this article as: Landing, Ed, Geyer, Gerd, Comment on “Terreneuvian small shelly faunas of east Yunnan (South China) and their biostratigraphic implications” by B. Yang et al. [Palaeogeography, Palaeoclimatology, Palaeoecology 398 (2014) 28–58], Palaeogeography, Palaeoclimatology, Palaeoecology (2016), doi: 10.1016/j.palaeo.2016.04.016
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Comment on “Terreneuvian small shelly faunas of east Yunnan (South China)
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Palaeoclimatology, Palaeoecology 398 (2014) 28–58]
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and their biostratigraphic implications” by B. Yang et al. [Palaeogeography,
New York State Museum, 222 Madison Avenue, Albany, NY 12230, USA.i
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a
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Ed Landinga and Gerd Geyerb
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b Institut für Geographie und Geologie, Lehrstuhl für Geodynamik und Geomaterial forschung,
Germany.
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Bayerische Julius-Maximilians-Universität Würzburg,, Am Hubland, 97074 Würzburg,
Corresponding author. E-mail: [email protected]. Tel: 518-473-8071
ACCEPTED MANUSCRIPT The Cambrian is the only Phanerozoic system that lacks a complete succession of global, formally defined chronostratigraphic subdivisions (i.e., series and stages, see Gradstein et al., 2012). The early
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Cambrian brackets key developments in metazoan evolution (i.e., appearance of deep, behaviorally complex burrows; biomineralized metazoan diversification; “modernization” of marine communities with
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the appearance of such biomineralized arthropods as trilobites; e.g., Droser et al., 2002, 2004; Landing
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and Westrop, 2004; Magano and Bautois, 2014). The Yang et al. (2014) report is important for its review of litho- and biostratigraphic developments on the southern Yangtze Platform that help illustrate early
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biomineralized metazoan diversification. Yang et al. (2014) further an understanding of the relative stratigraphic completeness of the thin and quite condensed succession on the tropical Yangtze Platform
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through the lowest Cambrian―or the Terreneuvian Series and its lowest Fortunian Stage and overlying
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Cambrian Stage 2/Laolinian Stage (Landing et al., 2007; 2013a, b, c).
The Yang et al. (2014) report roughly coincides with an interval of more intense discussion of lowest
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Cambrian chronostratigraphy. Thus, it was important for Yang et al. (2014) to cite existing chronostratigraphic syntheses, including a number authored by EL and GG (cited below) that were available early in 2013 and before publication of the Yang et al. (2014) report. Accurate inclusion of such syntheses would have provided a more accurate discussion and useful documentation of the extant controversies in lowest Cambrian chronostratigraphy and correlations for the history of science.
Yuan et al.’s (2014, figs. 1, 10, 11) regional litho- and biostratigraphic synthesis actually complements Landing and Geyer’s (2012) and Landing et al.’s (2013a, b, e) synthesis that the most complete lowest Cambrian sections in Yunnan Province lie to the north on the Yangtze Platform. In addition, a wellknown section near Laolin village provides a particularly useful succession through the upper Terreneuvian.
ACCEPTED MANUSCRIPT Using available faunal, lithostratigraphic, and δ13C data, Landing and Geyer (2012) and Landing et al. (2013b, e) proposed to the International Subcommission on Cambrian Stratigraphy (ISCS) and its
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Working Group on Stage 2 (“WG2”) that the Laolin roadcut features a horizon suitable for global correlation of a Stage 2 base. This horizon is defined by the peak of the L4 δ13C excursion within the
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Watsonella crosbyi Assemblage Zone (e.g., Steiner et al., 2004, 2007). This horizon is well above a local
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bedding plane-parallel thrust fault that does not truncate the section (also Yang et al., 2014, fig. 10). Landing et al. (2013a, e) also proposed a “Laolinian Stage” as a replacement for informal Cambrian Stage
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2. Landing et al. (2013d), in a proposal to the ISCS and WG 3, defined the cap of a global Laolinian Stage
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by the peak of the Siberian IV δ13C excursion, which itself is in the lower Repinaella Zone (trilobites). Finally, Landing et al. (2013c, e) completed a lower Cambrian chronostratigraphic division by proposing 13
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the Lenaldanian Series and Zhurinskyan Stage with their coterminous GSSPs at the peak of the IV δ C
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Cambrian and its lower stage).
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excursion to replace informal Series 2 and Stage 3 (roughly the traditional trilobite-bearing lower
The proposal that defined the Cambrian Stage 2 basal horizon (Geyer and Landing, 2012; Landing et al., 2013b, e) followed all the requirements for definition of a chronostratigraphic unit’s base (e.g., concept, multiple criteria for definition, age, stratotype location,described lithostratigraphic succession, access; see Cowie, 1986; Cowie et al., 1986). Similarly, the proposal of the Laolinian Stage GSSP (Landing et al., 2013a, e) completely followed Salvador (1994) and Remane et al. (1996, Section 5. Procedure for the submission of a GSSP) in submitting the proposal to the “concerned Subcommission”) and, actually unnecessarily by I.U.G.S. and I.C.S. requirements, to WG2.
The lay reader may be mislead by Yang et al.’s (2014, p. 52) conclusion that the Landing and Geyer (2012) proposal “lack(s) stratigraphic control.” Indeed, all proposals related to the Laolinian Stage (Landing and Geyer, 2012; Landing et al., 2013a, b, e) place its basal GSSP 9.4 m below the top of the
ACCEPTED MANUSCRIPT Dahai Member, at the peak of the L4 carbon isotope excursion at the Laolin roadcut, and at 174.6 m in the
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Laolin succession. This lithostratigraphic precision was somehow disregarded by Yang et al. (2014)
The authors of the Laolinian and Laolinian-related proposals are “old hands” when it comes to precise
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stratigraphic control for GSSP definitions. Most of the co-authors (Brasier, Geyer, Landing) were officers
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or voting members of the Precambrian‒ Cambrian Boundary Working Group and ISCS. Thus, Landing co-authored the Ediacaran‒ Cambrian boundary proposal (Narbonne et al., 1989) and its slight
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modification (Landing et al., 2013e) and was the primary author of the regional Placentian and Branchian
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Series of the lower Cambrian (Landing et al., 1989; Landing, 1992), the lowest Cambrian Terreneuvian Series and Fortunian Stage (Landing et al., 2007), the Lenaldanian Series and its Zhurinskyan Stage (Landing et al., 2013c, e), and the original proposal of the Lawsonian Stage as a replacement for informal
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Cambrian Stage 10 (Landing et al., 2010, 2011). All of these proposals precisely located GSSP horizons in measured, named stratigraphic sections. Actually it is Yang et al. (2014) who provide relatively
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minimal stratigraphic information for their biostratigraphic zones and subzones, and define them solely by faunal content and illustrate their range in generalized lithostratigraphic figures.
Given the proposals of a base of a global Stage 2 and the formal submission of a proposed Laolinian Stage to the ISCS and WG2 (i.e., Landing and Geyer, 2012; Landing et al, 2013a, b, e), Yang et al.’s (2014, p. 53) statement that our proposal must be “rejected for formal and scientific reasons” is puzzling and serves only to confound readers. As detailed above, all “formal” procedures for submission of the proposed base of Stage 2 as well as the proposal of the Laolinian GSSP to the ISCS and WG2 were made through the Landing and Geyer (2012) and Landing et al. (2013a, b, e) reports. It needs to be emphasized that the introduction of working groups for the relevant Cambrian stages followed the Cambrian subdivision initiative launched to define practical and suitable series and stages on a global scale (Geyer and Shergold, 2000; Shergold and Geyer, 2003). Such working groups were created to provide
ACCEPTED MANUSCRIPT recommendations to the subcommission’s officers and voting members, but by no means were intended to
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have executive power or make decisions.
Yang et al. (2014) only cite the Landing and Geyer (2012) abstract in their comments. Thus, they may be
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unfamiliar with the fact that while an abstract may inform participants at a meeting, it does not constitute
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a formal proposal of a chronostratigraphic unit or its base (Remane et al., 1996). The Landing and Geyer (2012) abstract is an irrelevant “straw horse” in the Yang et al. (2014) discussion, and Yang et al. (2014)
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should have included (the uncited) 2013 reports (Landing et al., 2013a, b, e) in their paper. As the ISCS
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and WG 2 and had received the Laolinian and Laolinian-related proposals in early 2013.
Contra Yang et al. (2014, p. 53), it is puzzling to read that the Laolinian and Laolinian-related proposals
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did not get “discussion in the relevant international working groups.” Indeed, the Landing and Geyer (2012) informal proposal (i.e., an abstract) was made at the ISCS meeting in Guizhou, and a PDF of the
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figures of the PowerPoint presentation and its text was sent to all WG2 members as part of an attempt at “discussion.” Secondly, the formal proposals for definition of the Stage 2 base and GSSP for the Laolinian Stage were submitted to WG2 and the ISCS by Landing et al. (2013a, b) as a further attempt at “discussion.” Thirdly, the Laolinian Stage proposal was published as a peer-reviewed article (Landing et al., 2013e)―another attempt at “discussion.” A number of opportunities for “discussion” by the “relevant international working groups” was initiated by co-authors E. Landing, G. Geyer, M. Brasier, A. Maloof, and S. A. Bowring, though Yang et al. (2014) conclude that no discussion took place.
Yang et al. (2014) invoke a procedure (i.e., “discussion”) that is not included as part of any formal/published process for proposal and submission of a chronostratigaphic unit. Remane et al. (1996) say nothing about “discussion” by any “relevant group.” We would have liked, and still encourage, a discussion of our many proposals by the ISCS and WG 2―the “relevant international working groups.”
ACCEPTED MANUSCRIPT Yang et al. (2014, p. 52) state that the Landing and Geyer (2012) proposal is “entirely (based) on carbon isotope markers” and “abandon(ed) any biostratigraphical subdivision for the early Cambrian.” Of
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course, basing chronostratigraphic units solely on carbon isotope markers is not a problem. Indeed, the Ediacaran base is correlated globally by a carbon isotope excursion (e.g., Knoll et al., 2001) and the base
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of the Ypresian Stage of the Paleogene is defined by a carbon isotope excursion (e.g., Gradstein et al.,
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2008).
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Yang et al. (2014) apparently did not appreciate that the Landing and Geyer (2012) and Landing et al.
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(2013a, b, e) proposal is based on the peak of the L4 carbon isotope excursion within the Watsonella crosbyi Assemblage Zone at Laolin. Rather, this is an integrated biostratigraphic-chemostratigraphically defined basal horizon and GSSP with specified biostratigraphic brackets (i.e., within the Watsonella
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crosbyi Assemblage Zone). The definition of the Laolinian Stage basal GSSP is not merely a geochemical
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“squiggle” and biostratigraphy was not “abandoned.”
Yang et al.’s (2014) comment that the base of Stage 2 and Laolinian Stage proposals “lack scientific data as correlation tools” can only be perceived as a derogatory comment by the lay reader. Yang et al. (2014) never discuss the reason for use of the peak of the L4 carbon isotope excursion as part of the definition of the Laolinian Stage basal GSSP, and simply seem to deride its use. As an aside, it might be noted that although chronostratigraphic boundary stratotypes should be proposed in marine fossiliferous sections (Cowie et al., 1986, section 3) there is no requirement that the horizon and point be defined by a fossil.
Geyer and Landing (2012) and Landing et al. (2013a, b, e, uncited by Yang et al., 2014) detailed that simple use of the FAD (first, actually “lowest,” appearance datum of a fossil taxon at a section is inherently problematical (e.g., Cowie et al., 1986, section I.3). The lowest known
ACCEPTED MANUSCRIPT occurrence of a fossil in any section is controlled by factors (immigration history, preservation, thoroughness of collecting, appropriate habitat) that always lead to underestimating the fossil’s
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lowest occurrence ( e.g., Landing et al., 2013e). As discussed below, the evidence actually reveals that the Yang et al. (2014, p, 52) correlation synthesis “lacks significant scientific data as
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correlation tools.” To begin with, simple mathematical calculations (Marshall, 1990) allow
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determination of how much lower a taxon might occur in a lithofacially uniform section (i.e., its
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confidence interval).
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Using Yang et al.’s (2014) Laolin data, a 95% confidence interval puts the lowest likely horizon with Watsonella crosbyi 20.5 m below the lowest known W. crosbyi and at about the base of the
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Dahai Member. Similarly, a 95% confidence interval puts the lowest likely occurrence of W. crosbyi at ca. 9 m below the lowest known specimens at their Lishuping section, and, again, at
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the base of the Dahai Member. This likely coincidence with a lithofacies break indicates that a W. crosbyi GSSP horizon be unstable and would fall to lower horizons with further collecting. Indeed, the local occurrence of W. crosbyi likely tracks lithofacies (Landing and Kouchinsky, 2016).
To escape the problems that can arise from the use of a simple biostratigraphic “FAD” of Watsonella crosbyi to define the base of a global Stage 2/Laolinian Stage, Landing and Geyer (2012) and Landing et al. (2013a, b, e) noted that the L4/P4/ZHUCE carbon isotope excursions serve as coeval markers across South China and can be correlated into the I’ excursion in the upper ‘Nemakit-Daldynian’ of NW Siberia (Li et al., 2009). The utility of a carbon isotope excursion in upper Terreneuvian correlations from South China into Siberia, western Mongolia
ACCEPTED MANUSCRIPT and Avalonia has been further developed recently (Landing et al., 2013e; Smith et al., 2015). Yang et al. (2014) were premature in rejecting the Geyer and Landing (2012) proposal “for …
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scientific reasons” in that it lacked significant scientific data as correlation tools.” Yang et al.
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(2014) somehow were unaware of or declined to evaluate the Li et al. (2009) correlations, which
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have been further confirmed by Landing and Kouchinsky (2016).
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Yang et al. (2014, p. 52) claim that the Laolinian Stage is based on the positive carbon isotope excursion “… that starts in the lower Dahai Member at Xiotan and the middle Dahai Member of the Laolin section.”
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Simply stated, the Yang et al. (2014) statement is incorrect. The Laolinian GSSP base is not defined by the whole isotope excursion, but only by its peak within the W. crosbyi Assemblage Zone. Again, the text
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of Landing and Geyer (2012) and Landing et al. (2013a, 2013b) should be cited accurately.
There are limitations to the length of a “Comment,” and it should be noted that a number of Yang et al.
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(2014) comments are incorrect when they venture outside of the superlatively described and interpreted lithostratigraphy and biostratigraphy of the southern Yangtze Platform. An obvious comment can be made about the first page of their report (Yang et al., 2014, p. 28) where opposition to the use of the “FAD” of the ichnofossil Trichophycus pedum to define the base of the Cambrian is noted. Yang et al. (2014) claim the taxon can only be used as part of the definition of the base of the Cambrian in “Avalonia, Baltica, and parts of Laurentia.” The reviewers should know that the distribution of T. pedum also includes East Gondwana (Australia, northern Iran, Oman, Namibia, Argentina), West Gondwana (Iberia), and locally appears on the the Siberian platform, with the South China occurrences close to the BACE carbon excursion (Landing et al., 2013e, 2015a, 2015b). In any case, Landing et al. (2013e) also emphasized that a T. pedum Assemblage Zone, not a T. pedum FAD, with a base above the highest characteristic Ediacaran taxa (e.g., Harlaniella, Palaeopasichnus) best defines the base of the Cambrian.
References
ACCEPTED MANUSCRIPT Cowie, J.W., 1986.Guidelines for boundary stratotypes. Episodes 9, 78–82. Cowie, J.W., Ziegler, W., Boucot, A.J., Bassett, M.G., Remane, J., 1986. Guidelines and statutes
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ACCEPTED MANUSCRIPT Cambrian Stratigraphy and Paleontology of Guizou, China. The 17th field conference of the Cambrian Stage Subdivision Working Group, International Subcommission on Cambrian
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fossil (SSF) taxa, and chronostratigraphic significance. Geol. Mag. 153, 7 p.
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Landing, E., Peng, S.C., Babcock, L.E., Geyer, G., Moczydłowska-Vidal, M., 2007. Global
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Landing, E., Westrop, S.R., Miller, J.F., 2010. Globally practical base for the uppermost Cambrian (Stage 10): FAD of the conodont Eoconodontus notchpeakensis and the Housian [sic, read “Lawsonian”] Stage. In: O. Fatka, O., Budil, P. (Eds.), The 15th Field Conference of the Cambrian Stage Subdivision Working Group. Abstracts and Excursion Guide, Prague Czech Repubic and south-eastern Germany.Czech Geological Survey, p. 18. Landing, E., Westrop, S.R. Adrain, J.M., 2011 The Lawsonian Stage—the Eoconodontus notchpeakensis (Miller, 1969) FAD and HERB carbon isotope excursion define a globally correlatable terminal Cambrian stage. Bull. Geosci., Czech Geological Survey 86, 621–640.
ACCEPTED MANUSCRIPT Landing, E., Geyer, G., Maloof, A. C., Brasier, M. B., Bowring, S. A., 2013a. Proposed global stratotype section and point (GSSP) for the Laolinian Stage as the upper stage of the
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Terreveuvian Series. Proposal submitted to ICS and WG2, 49 p. Landing, E., Geyer, G., Brasier, M.D., Bowring, S. A., 2013b. Base of Global Cambrian Stage 2: carbon-
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Proposal submitted to ICS and WG2, 51 p.
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Landing, E., Geyer, G., Maloof, A. C., Brasier, M. B., Bowring, S. A., 2013c. Proposed GSSP (Global Stratotype Section and Point) for the Lenaldanian Series and Zhurinskyan Stage
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(=informal Cambrian Series 2 and 3; upper part of the traditional Lower Cambrian. Proposal submitted to ISC and WG3, 52 p.
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Landing, E., Geyer, G., Brasier, M.D., Bowring, S. A., 2013d. Proposed base of global Cambrian Series 2
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Landing, E., Geyer, G., Brasier, M.D., Bowring, S. A., 2013e. Cambrian Evolutionary Radiation: context, correlation, and chronostratigraphy —overcoming deficiencies of the first appearance datum (FAD) concept. Earth-Sci. Rev. 123, 133–172. Landing, E., Geyer, G., Bautuois, L., 2015a. Demonstrated long-term utility of the basal Cambrian GSSP at Fortune Head, eastern Newfoundland. Strati―Second international Congress on Stratigraphy. Berichte des Inst. für Erdwissenschaften Karl-Franzen-Univ., 21,221. ISSN 1608-8166. Landing, E., Kouchinsky, A., Westrop, S. R., Geyer, G., 2015b. 10 m.y. evolutionary stasis of earliest Cambrian (Terreneuvian) mollusk-rich faunas and Cambrian Evolutionary Radiation correlations. Geol. Soc. America, Abstr. Prog., 47(7):23.
ACCEPTED MANUSCRIPT Li, D., Ling, H.F., Jiang, S.Y., Pan, J.Y., Chen, Y.Q., Cai, Y.F., Feng, H.Z., 2009. New carbon isotope stratigraphy of the Ediacaran–Cambrian boundary interval from SW China:
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Smith, E.F., Macdonald, F.A., Petach, T.A., Bold, U., Schrag, D.P., 2015. Integrated stratigraphic, geochemical, and paleontological late Ediacaran to early Cambrian record from southwestern Mongolia. Geol. Soc. America Bull.. doi: 10.1130/B31248.1 Steiner, M., Li, G.X., Qian, Y., Zhu, M.Y., 2004. Lower Cambrian small shelly fossils of northern Sichuan and southern Shaanxi (China), and their biostratigraphic significance. Géobios 37, 259–275. Steiner, M., Li, G.X., Qian, Y., Zhu, M.Y., Erdtmann, B.-D., 2007. Neoproterozoic to early Cambrian small shelly fossil assemblages and a revised biostratigraphic correlation of the Yangtze Platform (China). Palaeogeogr, Palaeoclimatol, Palaeoecol 254, 67–99.
ACCEPTED MANUSCRIPT Yang, B., Steiner, M., Li., G., Keupp, H., 2014. Terreneuvian small shelly fossils of East Yunnan (South China) and their biostratigraphic implications. Palaeogeogr., Palaeoclimatol.,
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Palaeoecol. 398, 28‒ 58.
S0031-0182(16)30071-2 doi: 10.1016/j.palaeo.2016.04.016 PALAEO 7782
To appear in:
Palaeogeography, Palaeoclimatology, Palaeoecology
Received date: Revised date: Accepted date:
25 February 2016 29 March 2016 5 April 2016
Please cite this article as: Landing, Ed, Geyer, Gerd, Comment on “Terreneuvian small shelly faunas of east Yunnan (South China) and their biostratigraphic implications” by B. Yang et al. [Palaeogeography, Palaeoclimatology, Palaeoecology 398 (2014) 28–58], Palaeogeography, Palaeoclimatology, Palaeoecology (2016), doi: 10.1016/j.palaeo.2016.04.016
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Comment on “Terreneuvian small shelly faunas of east Yunnan (South China)
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Palaeoclimatology, Palaeoecology 398 (2014) 28–58]
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and their biostratigraphic implications” by B. Yang et al. [Palaeogeography,
New York State Museum, 222 Madison Avenue, Albany, NY 12230, USA.i
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a
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Ed Landinga and Gerd Geyerb
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b Institut für Geographie und Geologie, Lehrstuhl für Geodynamik und Geomaterial forschung,
Germany.
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Bayerische Julius-Maximilians-Universität Würzburg,, Am Hubland, 97074 Würzburg,
Corresponding author. E-mail: [email protected]. Tel: 518-473-8071
ACCEPTED MANUSCRIPT The Cambrian is the only Phanerozoic system that lacks a complete succession of global, formally defined chronostratigraphic subdivisions (i.e., series and stages, see Gradstein et al., 2012). The early
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Cambrian brackets key developments in metazoan evolution (i.e., appearance of deep, behaviorally complex burrows; biomineralized metazoan diversification; “modernization” of marine communities with
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the appearance of such biomineralized arthropods as trilobites; e.g., Droser et al., 2002, 2004; Landing
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and Westrop, 2004; Magano and Bautois, 2014). The Yang et al. (2014) report is important for its review of litho- and biostratigraphic developments on the southern Yangtze Platform that help illustrate early
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biomineralized metazoan diversification. Yang et al. (2014) further an understanding of the relative stratigraphic completeness of the thin and quite condensed succession on the tropical Yangtze Platform
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through the lowest Cambrian―or the Terreneuvian Series and its lowest Fortunian Stage and overlying
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Cambrian Stage 2/Laolinian Stage (Landing et al., 2007; 2013a, b, c).
The Yang et al. (2014) report roughly coincides with an interval of more intense discussion of lowest
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Cambrian chronostratigraphy. Thus, it was important for Yang et al. (2014) to cite existing chronostratigraphic syntheses, including a number authored by EL and GG (cited below) that were available early in 2013 and before publication of the Yang et al. (2014) report. Accurate inclusion of such syntheses would have provided a more accurate discussion and useful documentation of the extant controversies in lowest Cambrian chronostratigraphy and correlations for the history of science.
Yuan et al.’s (2014, figs. 1, 10, 11) regional litho- and biostratigraphic synthesis actually complements Landing and Geyer’s (2012) and Landing et al.’s (2013a, b, e) synthesis that the most complete lowest Cambrian sections in Yunnan Province lie to the north on the Yangtze Platform. In addition, a wellknown section near Laolin village provides a particularly useful succession through the upper Terreneuvian.
ACCEPTED MANUSCRIPT Using available faunal, lithostratigraphic, and δ13C data, Landing and Geyer (2012) and Landing et al. (2013b, e) proposed to the International Subcommission on Cambrian Stratigraphy (ISCS) and its
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Working Group on Stage 2 (“WG2”) that the Laolin roadcut features a horizon suitable for global correlation of a Stage 2 base. This horizon is defined by the peak of the L4 δ13C excursion within the
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Watsonella crosbyi Assemblage Zone (e.g., Steiner et al., 2004, 2007). This horizon is well above a local
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bedding plane-parallel thrust fault that does not truncate the section (also Yang et al., 2014, fig. 10). Landing et al. (2013a, e) also proposed a “Laolinian Stage” as a replacement for informal Cambrian Stage
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2. Landing et al. (2013d), in a proposal to the ISCS and WG 3, defined the cap of a global Laolinian Stage
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by the peak of the Siberian IV δ13C excursion, which itself is in the lower Repinaella Zone (trilobites). Finally, Landing et al. (2013c, e) completed a lower Cambrian chronostratigraphic division by proposing 13
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the Lenaldanian Series and Zhurinskyan Stage with their coterminous GSSPs at the peak of the IV δ C
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Cambrian and its lower stage).
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excursion to replace informal Series 2 and Stage 3 (roughly the traditional trilobite-bearing lower
The proposal that defined the Cambrian Stage 2 basal horizon (Geyer and Landing, 2012; Landing et al., 2013b, e) followed all the requirements for definition of a chronostratigraphic unit’s base (e.g., concept, multiple criteria for definition, age, stratotype location,described lithostratigraphic succession, access; see Cowie, 1986; Cowie et al., 1986). Similarly, the proposal of the Laolinian Stage GSSP (Landing et al., 2013a, e) completely followed Salvador (1994) and Remane et al. (1996, Section 5. Procedure for the submission of a GSSP) in submitting the proposal to the “concerned Subcommission”) and, actually unnecessarily by I.U.G.S. and I.C.S. requirements, to WG2.
The lay reader may be mislead by Yang et al.’s (2014, p. 52) conclusion that the Landing and Geyer (2012) proposal “lack(s) stratigraphic control.” Indeed, all proposals related to the Laolinian Stage (Landing and Geyer, 2012; Landing et al., 2013a, b, e) place its basal GSSP 9.4 m below the top of the
ACCEPTED MANUSCRIPT Dahai Member, at the peak of the L4 carbon isotope excursion at the Laolin roadcut, and at 174.6 m in the
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Laolin succession. This lithostratigraphic precision was somehow disregarded by Yang et al. (2014)
The authors of the Laolinian and Laolinian-related proposals are “old hands” when it comes to precise
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stratigraphic control for GSSP definitions. Most of the co-authors (Brasier, Geyer, Landing) were officers
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or voting members of the Precambrian‒ Cambrian Boundary Working Group and ISCS. Thus, Landing co-authored the Ediacaran‒ Cambrian boundary proposal (Narbonne et al., 1989) and its slight
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modification (Landing et al., 2013e) and was the primary author of the regional Placentian and Branchian
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Series of the lower Cambrian (Landing et al., 1989; Landing, 1992), the lowest Cambrian Terreneuvian Series and Fortunian Stage (Landing et al., 2007), the Lenaldanian Series and its Zhurinskyan Stage (Landing et al., 2013c, e), and the original proposal of the Lawsonian Stage as a replacement for informal
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Cambrian Stage 10 (Landing et al., 2010, 2011). All of these proposals precisely located GSSP horizons in measured, named stratigraphic sections. Actually it is Yang et al. (2014) who provide relatively
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minimal stratigraphic information for their biostratigraphic zones and subzones, and define them solely by faunal content and illustrate their range in generalized lithostratigraphic figures.
Given the proposals of a base of a global Stage 2 and the formal submission of a proposed Laolinian Stage to the ISCS and WG2 (i.e., Landing and Geyer, 2012; Landing et al, 2013a, b, e), Yang et al.’s (2014, p. 53) statement that our proposal must be “rejected for formal and scientific reasons” is puzzling and serves only to confound readers. As detailed above, all “formal” procedures for submission of the proposed base of Stage 2 as well as the proposal of the Laolinian GSSP to the ISCS and WG2 were made through the Landing and Geyer (2012) and Landing et al. (2013a, b, e) reports. It needs to be emphasized that the introduction of working groups for the relevant Cambrian stages followed the Cambrian subdivision initiative launched to define practical and suitable series and stages on a global scale (Geyer and Shergold, 2000; Shergold and Geyer, 2003). Such working groups were created to provide
ACCEPTED MANUSCRIPT recommendations to the subcommission’s officers and voting members, but by no means were intended to
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have executive power or make decisions.
Yang et al. (2014) only cite the Landing and Geyer (2012) abstract in their comments. Thus, they may be
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unfamiliar with the fact that while an abstract may inform participants at a meeting, it does not constitute
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a formal proposal of a chronostratigraphic unit or its base (Remane et al., 1996). The Landing and Geyer (2012) abstract is an irrelevant “straw horse” in the Yang et al. (2014) discussion, and Yang et al. (2014)
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should have included (the uncited) 2013 reports (Landing et al., 2013a, b, e) in their paper. As the ISCS
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and WG 2 and had received the Laolinian and Laolinian-related proposals in early 2013.
Contra Yang et al. (2014, p. 53), it is puzzling to read that the Laolinian and Laolinian-related proposals
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did not get “discussion in the relevant international working groups.” Indeed, the Landing and Geyer (2012) informal proposal (i.e., an abstract) was made at the ISCS meeting in Guizhou, and a PDF of the
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figures of the PowerPoint presentation and its text was sent to all WG2 members as part of an attempt at “discussion.” Secondly, the formal proposals for definition of the Stage 2 base and GSSP for the Laolinian Stage were submitted to WG2 and the ISCS by Landing et al. (2013a, b) as a further attempt at “discussion.” Thirdly, the Laolinian Stage proposal was published as a peer-reviewed article (Landing et al., 2013e)―another attempt at “discussion.” A number of opportunities for “discussion” by the “relevant international working groups” was initiated by co-authors E. Landing, G. Geyer, M. Brasier, A. Maloof, and S. A. Bowring, though Yang et al. (2014) conclude that no discussion took place.
Yang et al. (2014) invoke a procedure (i.e., “discussion”) that is not included as part of any formal/published process for proposal and submission of a chronostratigaphic unit. Remane et al. (1996) say nothing about “discussion” by any “relevant group.” We would have liked, and still encourage, a discussion of our many proposals by the ISCS and WG 2―the “relevant international working groups.”
ACCEPTED MANUSCRIPT Yang et al. (2014, p. 52) state that the Landing and Geyer (2012) proposal is “entirely (based) on carbon isotope markers” and “abandon(ed) any biostratigraphical subdivision for the early Cambrian.” Of
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course, basing chronostratigraphic units solely on carbon isotope markers is not a problem. Indeed, the Ediacaran base is correlated globally by a carbon isotope excursion (e.g., Knoll et al., 2001) and the base
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of the Ypresian Stage of the Paleogene is defined by a carbon isotope excursion (e.g., Gradstein et al.,
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2008).
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Yang et al. (2014) apparently did not appreciate that the Landing and Geyer (2012) and Landing et al.
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(2013a, b, e) proposal is based on the peak of the L4 carbon isotope excursion within the Watsonella crosbyi Assemblage Zone at Laolin. Rather, this is an integrated biostratigraphic-chemostratigraphically defined basal horizon and GSSP with specified biostratigraphic brackets (i.e., within the Watsonella
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crosbyi Assemblage Zone). The definition of the Laolinian Stage basal GSSP is not merely a geochemical
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“squiggle” and biostratigraphy was not “abandoned.”
Yang et al.’s (2014) comment that the base of Stage 2 and Laolinian Stage proposals “lack scientific data as correlation tools” can only be perceived as a derogatory comment by the lay reader. Yang et al. (2014) never discuss the reason for use of the peak of the L4 carbon isotope excursion as part of the definition of the Laolinian Stage basal GSSP, and simply seem to deride its use. As an aside, it might be noted that although chronostratigraphic boundary stratotypes should be proposed in marine fossiliferous sections (Cowie et al., 1986, section 3) there is no requirement that the horizon and point be defined by a fossil.
Geyer and Landing (2012) and Landing et al. (2013a, b, e, uncited by Yang et al., 2014) detailed that simple use of the FAD (first, actually “lowest,” appearance datum of a fossil taxon at a section is inherently problematical (e.g., Cowie et al., 1986, section I.3). The lowest known
ACCEPTED MANUSCRIPT occurrence of a fossil in any section is controlled by factors (immigration history, preservation, thoroughness of collecting, appropriate habitat) that always lead to underestimating the fossil’s
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lowest occurrence ( e.g., Landing et al., 2013e). As discussed below, the evidence actually reveals that the Yang et al. (2014, p, 52) correlation synthesis “lacks significant scientific data as
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correlation tools.” To begin with, simple mathematical calculations (Marshall, 1990) allow
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determination of how much lower a taxon might occur in a lithofacially uniform section (i.e., its
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confidence interval).
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Using Yang et al.’s (2014) Laolin data, a 95% confidence interval puts the lowest likely horizon with Watsonella crosbyi 20.5 m below the lowest known W. crosbyi and at about the base of the
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Dahai Member. Similarly, a 95% confidence interval puts the lowest likely occurrence of W. crosbyi at ca. 9 m below the lowest known specimens at their Lishuping section, and, again, at
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the base of the Dahai Member. This likely coincidence with a lithofacies break indicates that a W. crosbyi GSSP horizon be unstable and would fall to lower horizons with further collecting. Indeed, the local occurrence of W. crosbyi likely tracks lithofacies (Landing and Kouchinsky, 2016).
To escape the problems that can arise from the use of a simple biostratigraphic “FAD” of Watsonella crosbyi to define the base of a global Stage 2/Laolinian Stage, Landing and Geyer (2012) and Landing et al. (2013a, b, e) noted that the L4/P4/ZHUCE carbon isotope excursions serve as coeval markers across South China and can be correlated into the I’ excursion in the upper ‘Nemakit-Daldynian’ of NW Siberia (Li et al., 2009). The utility of a carbon isotope excursion in upper Terreneuvian correlations from South China into Siberia, western Mongolia
ACCEPTED MANUSCRIPT and Avalonia has been further developed recently (Landing et al., 2013e; Smith et al., 2015). Yang et al. (2014) were premature in rejecting the Geyer and Landing (2012) proposal “for …
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scientific reasons” in that it lacked significant scientific data as correlation tools.” Yang et al.
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(2014) somehow were unaware of or declined to evaluate the Li et al. (2009) correlations, which
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have been further confirmed by Landing and Kouchinsky (2016).
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Yang et al. (2014, p. 52) claim that the Laolinian Stage is based on the positive carbon isotope excursion “… that starts in the lower Dahai Member at Xiotan and the middle Dahai Member of the Laolin section.”
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Simply stated, the Yang et al. (2014) statement is incorrect. The Laolinian GSSP base is not defined by the whole isotope excursion, but only by its peak within the W. crosbyi Assemblage Zone. Again, the text
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of Landing and Geyer (2012) and Landing et al. (2013a, 2013b) should be cited accurately.
There are limitations to the length of a “Comment,” and it should be noted that a number of Yang et al.
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(2014) comments are incorrect when they venture outside of the superlatively described and interpreted lithostratigraphy and biostratigraphy of the southern Yangtze Platform. An obvious comment can be made about the first page of their report (Yang et al., 2014, p. 28) where opposition to the use of the “FAD” of the ichnofossil Trichophycus pedum to define the base of the Cambrian is noted. Yang et al. (2014) claim the taxon can only be used as part of the definition of the base of the Cambrian in “Avalonia, Baltica, and parts of Laurentia.” The reviewers should know that the distribution of T. pedum also includes East Gondwana (Australia, northern Iran, Oman, Namibia, Argentina), West Gondwana (Iberia), and locally appears on the the Siberian platform, with the South China occurrences close to the BACE carbon excursion (Landing et al., 2013e, 2015a, 2015b). In any case, Landing et al. (2013e) also emphasized that a T. pedum Assemblage Zone, not a T. pedum FAD, with a base above the highest characteristic Ediacaran taxa (e.g., Harlaniella, Palaeopasichnus) best defines the base of the Cambrian.
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