Downloaded from http://sp.lyellcollection.org/ by guest on October 2, 2021 The Permian timescale: an introduction SPENCER G. LUCAS1* & SHU-ZHONG SHEN2 1New Mexico Museum of Natural History and Science, 1801 Mountain Road NW, Albuquerque, NM 87104-1375, USA 2State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, 39 East Beijing Road, Nanjing, Jiangsu 210008, China *Correspondence: [email protected] Abstract: The Permian timescale has developed over about two centuries of research to the current chronostratigraphic scale advocated by the Subcommission on Permian Stratigraphy of three series and nine stages: Cisuralian (lower Permian) – Asselian, Sakmarian, Artinskian, Kun- gurian; Guadalupian (middle Permian) – Roadian, Wordian, Capitanian; and Lopingian (upper Permian) – Wuchiapingian and Changhsingian. The boundaries of the Permian System are defined by global stratotype sections and points (GSSPs) and the numerical ages of those boundaries appear to be determined with a precision better than 1‰. Nevertheless, much work remains to be done to refine the Permian timescale. Precise numerical age control within the Permian is very uneven and a global polarity timescale for the Permian is far from established. Chronostratigraphic definitions of three of the nine Permian stages remain unfinished and various issues of marine biostratigraphy are still unresolved. In the non-marine Permian realm, much progress has been made in correlation, especially using palynomorphs, megafossil plants, conchostracans and both the footprints and bones of tetrapods (amphibians and reptiles), but many problems of correlation remain, especially the cross-correlation of non-marine and marine chronologies. The further development of a Perm- ian chronostratigraphic scale faces various problems, including those of stability and priority of nomenclature and concepts, disagreements over changing taxonomy, ammonoid v. fusulinid v. conodont biostratigraphy, differences in the perceived significance of biotic events for chrono- stratigraphic classification and correlation problems between provinces. Future research on the Permian timescale should focus on GSSP selection for the remaining undefined stage bases, the definition and characterization of substages, and further development and integration of the Perm- ian chronostratigraphic scale with radioisotopic, magnetostratigraphic and chemostratigraphic tools for calibration and correlation. Gold Open Access: This article is published under the terms of the CC-BY 3.0 license. The Subcommission on Permian Stratigraphy This volume reviews the state of the art of the (SPS), part of the International Union of Geological Permian timescale and this introductory chapter Sciences International Commission on Stratigraphy, provides an overview of the book. It also presents currently advocates a Permian chronostratigraphic the current Permian timescale of the SPS. scale of three series and nine stages (Fig. 1). The boundaries of the Permian System and six of its nine stages are defined by global stratotype sections Permian chronostratigraphy and points (GSSPs). The numerical ages of the sys- tem boundaries appear to be determined with a pre- Lucas & Shen (2016) review the nearly two century cision better than 1‰, but precise numerical age long development of the Permian chronostrati- control within the Permian is generally sparse and graphic scale, which is now a hierarchy of three uneven. A global polarity timescale for the Permian series and nine stages (Fig. 1). In 1841, Murchison is being developed, but is not complete. Chronostra- coined the term Permian for strata in the Russian tigraphic definitions of most of the 13 substages Urals. Recognition of the Permian outside Russia used by some workers to subdivide the Permian and Central Europe soon followed, but it took stages remain unfinished. For the non-marine Perm- about a century for the Permian to be accepted glob- ian strata, correlations based on palynomorphs, con- ally as a distinct geological system. chostracans and tetrapods (amphibians and reptiles) The work of the SPS began in the 1970s and have been proposed, but many problems of correla- resulted in the current recognition of nine Permian tion remain, especially the cross-correlation of stages in three series: Cisuralian (lower Permian) – Permian non-marine and marine chronologies. Asselian, Sakmarian, Artinskian, Kungurian; From:Lucas,S.G.&Shen, S. Z. (eds) The Permian Timescale. Geological Society, London, Special Publications, 450, https://doi.org/10.1144/SP450.15, updated version # 2017 The Author(s). Published by The Geological Society of London. Publishing disclaimer: www.geolsoc.org.uk/pub_ethics Downloaded from http://sp.lyellcollection.org/ by guest on October 2, 2021 S. G. LUCAS & S. Z. SHEN Fig. 1. Permian chronostratigraphic scale showing the ratified GSSPs of the stage bases. Guadalupian (middle Permian) – Roadian, Wor- the rise of Permian conodont biostratigraphy so that dian, Capitanian; and Lopingian (upper Permian) – all Permian GSSPs now use conodont evolutionary Wuchiapingian and Changhsingian. The 1990s saw events as the primary signals for correlation. Most Downloaded from http://sp.lyellcollection.org/ by guest on October 2, 2021 THE PERMIAN TIMESCALE of the bases of the Permian stages have been defined Sw. aff. Sw. merrilli–Sw. binodosus–Sw. by GSSPs (Figs 1 & 2): anceps–Sw. aff. Sw. whitei (Chuvashov et al. 2013). (1) In 1998, the base of the Asselian (¼base of (4) There is no agreed GSSP for the base of the Permian) was defined by the GSSP at the Kungurian. Henderson et al. (2012a) pro- Aidaralash Creek in western Kazakstan posed the Rockland section near Wells, (Davydov et al. 1998). The primary criterion Nevada, USA, as a GSSP for the base of (signal) for correlation of the GSSP is the the Kungurian, where the primary signal first appearance datum (FAD) of the cono- for correlation is the FAD of the conodont dont Streptognathodus isolatus in the S. Neostreptognathodus pnevi in a lineage wabaunensis chronomorphocline. At Aidar- from Neostreptognathodus pequopensis to alash Creek, the lowest occurrence (LO) of N. pnevi. Chernykh et al. (2012) advocated S. isolatus is c. 6 m below the secondary sig- the Mechetlino section in Russia as the nal, which is the LO of the fusulinid Sphaer- GSSP candidate, with the same conodont oschwagerina fusiformis, and it is c. 27 m event as its primary signal. They recently below the traditional Asselian base deter- proposed moving the GSSP candidate sec- mined by ammonoid biostratigraphy (Bogo- tion to the nearby Mechetlino Quarry sec- slovskaya et al. 1995). tion, which has better rock quality for (2) There is no official GSSP to define the base conodonts and chemostratigraphy. of the Sakmarian, one of three Permian (5) The base of the Roadian Stage is defined by GSSPs that remain to be agreed. The most its GSSP in Stratotype Canyon, Guadalupe recent proposal is the Usolka section in Mountains National Park, Texas, USA. The southern Russia, where the primary signal primary signal for correlation is the FAD of for correlation is the FAD of the conodont the conodont Jinogondolella nankingensis, Mesogondolella monstra in the hypothesized hypothesized to have descended from its evolutionary lineage M. uralensis–M. mon- ancestors among Mesogondolella idahoen- stra–M. manifesta (Chernykh et al. 2016). sis lamberti (Glenister et al. 1999; Mei & (3) There is no ratified GSSP for the base of the Henderson 2002; Henderson et al. 2012b), Artinskian. The currently proposed GSSP for but the precise first occurrence of the serrated the base of the Artinskian Stage is the Dal’ny Jinogondolella needs to be investigated Tulkas section in southern Russia, with further. its primary signal for correlation the FAD (6) The base of the Wordian is now defined by of the conodont Sweetognathus aff. S. whitei its GSSP at Gateway near Guadalupe Pass in the hypothesized chronomorphocline in the Guadalupe Mountains National Park. Fig. 2. Permian world map showing the locations of ratified GSSPs of Permian stage bases after Lucas et al. (2006). Downloaded from http://sp.lyellcollection.org/ by guest on October 2, 2021 S. G. LUCAS & S. Z. SHEN Its primary signal for correlation is the FAD datable volcanic ash beds, in contrast with some of of the conodont Jinogondolella aserrata the other geological systems (such as the Creta- in a hypothesized lineage as the descendant ceous), which have a much more extensive record of J. nankingensis (Glenister et al. 1999; of volcanism. Nevertheless, some important advan- Mei & Henderson 2002; Henderson et al. ces have been made in the last two decades. The 2012b). However, this definition has not been Lopingian and the Permian–Triassic boundary confirmed by recent studies and needs to be have been best dated with high-precision chemi- studied further. cal abrasion isotope dilution thermal ionization (7) The base of the Capitanian is defined by mass spectrometry (Shen et al. 2011; Burgess its GSSP at Nipple Hill in the Guadalupe et al. 2014). A series of high-precision U–Pb Mountains National Park. Its primary signal dates were also obtained from many volcanic ash for correlation is the FAD of the conodont beds in the Asselian, Sakmarian and Artinskian in Jinogondolella postserrata within the hypo- the southern Urals (Schmitz & Davydov 2012). thesized lineage from J. nankingensis to A high-precision U–Pb age for the base of the J. aserrata to J. postserrata. However, very Guadalupian in South China has