Permian Palynostratigraphy: a Global Overview
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Downloaded from http://sp.lyellcollection.org/ by guest on October 1, 2021 Permian palynostratigraphy: a global overview MICHAEL H. STEPHENSON British Geological Survey, Keyworth, Nottingham NG12 5GG, UK (e-mail: [email protected]) Abstract: Permian palynostratigraphic schemes are used primarily to correlate coal- and hydro- carbon-bearing rocks within basins and between basins, sometimes at high levels of biostrati- graphic resolution. Up to now, their main shortcoming has been the lack of correlation with schemes outside the basins, coalfields and hydrocarbon fields that they serve, and chiefly a lack of correlation with the international Permian scale. This is partly because of phytogeographical provinciality from the Guadalupian onwards, making correlation between regional palynostrati- graphic schemes difficult. However, local high-resolution palynostratigraphic schemes for regions are now being linked either by assemblage-level quantitative taxonomic comparison or by the use of single well-characterized palynological taxa that occur across Permian phytogeographical provinces. Such taxa include: Scutasporites spp., Vittatina spp., Weylandites spp., Lueckisporites virkkiae, Otynisporites eotriassicus and Converrucosisporites confluens. These palynological cor- relations are being facilitated and supplemented with radiometric, magnetostratigraphic, indepen- dent faunal and strontium isotopic dating. Gold Open Access: This article is published under the terms of the CC-BY 3.0 license Palynostratigraphy is the use of palynomorphs important biostratigraphic markers for the Permian (defined as organic-walled microfossils 5–500 mm of Gondwana and include several hundred species. in diameter) in correlating and assigning relative It is estimated that by the Lopingian about 60% of ages to rock strata. As such, it is a branch of biostra- the world’s flora consisted of seed plants (Gradstein tigraphy and follows the rules of biostratigraphic & Kerp 2012). practice: for example, those set out by Rawson These large-scale evolutionary changes in plants, et al. (2002). filtered by local and regional effects, are responsible The Permian, falling between 252.2 and 298.9 Ma, for the palynological succession that provides was a period of intense change in which the giant opportunities for subdivision on which palynostrati- continent of Pangea as a whole moved north, and graphic schemes are built. However, the pro- in which, through the early part of the Period, a tran- nounced phytogeographical differentiation of the sition from icehouse to greenhouse conditions occur- Permian has a powerful effect on palynostratigra- red (e.g. Fielding et al. 2008), alongside the decline phy, such that schemes differ considerably across in coal swamps and the establishment of widespread Pangea and correlation between schemes is even evaporite deposits (Henderson et al. 2012). The end now tentative or incomplete. In the Gondwana phy- of the Period saw a major extinction of fauna such as togeographical province, for example, it is difficult fusulinacean foraminifers, trilobites, rugose and tab- to correlate to the standard Permian stages; and ulate corals, blastoids, acanthodians, placoderms, the Carboniferous–Permian and Permian–Triassic and pelycosaurs; a dramatic reduction in bryozoans, boundaries are not precisely correlateable into brachiopods, ammonoids, sharks, bony fish, cri- Gondwana basins using palynology (Stephenson noids, eurypterids, ostracodes and echinoderms 2008a). (Henderson et al. 2012); and, although many coni- Until recently, progress in correlation was ham- fers (e.g. glossopterids, cordaites) became extinct pered by the lack of fundamental stratigraphic stan- at the end of the Permian, there is no evidence of dards such as stage Global Stratigraphic Sections major extinction in the plants (Gradstein & Kerp and Points (GSSPs); however, since 1997 (Jin 2012). Amongst the most important changes in et al. 1997; Henderson et al. 2012) a number of land plants is the replacement, near the end of the GSSPs have been established within the Pennsylva- Carboniferous, of arborescent lycophytes by arbo- nian–Permian succession, the most important of rescent tree ferns; arborescent lycophytes only which is the basal Permian GSSP at Aidaralash persisted into the Guadalupian in China. The arbo- Creek in the southern Urals (Jin et al. 1997; Hender- rescent horsetails also declined by the end of the Car- son et al. 2012), and the basal Triassic GSSP at boniferous. In the Permian, a great variety of new Meishan section D, Changxing County, Zhejiang seed plant groups appeared such as cycads, ginkgos, Province, South China (Yin et al. 2001). Since voltzialean conifers and glossopterids. The latter are these developments, there have also been other From:Lucas,S.G.&Shen, S. Z. (eds) The Permian Timescale. Geological Society, London, Special Publications, 450, https://doi.org/10.1144/SP450.2 # 2016 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 1, 2021 M. H. STEPHENSON advances contributing to the precision and utility of The approach taken in this paper is to sur- palynological biostratigraphy in this interval, vey the palynostratigraphic schemes in the main including radiometric and faunal dating of palyno- phytogeographic provinces and then to attempt logical biozones, and limited high-resolution corre- synthesis; and so the focus is on palynostratigraphy lation between continents using a well-defined not taxonomy. Given the plethora of palynological palynological species. literature on this interval, the review is necessarily Palynological research in the Permian is exten- selective. Most recent published palynostratigraphic sive, being partly driven by exploration for coal (e.g. schemes (e.g. since 2000) have emanated from in India and Australia), and oil and gas (e.g. in the South American and Middle Eastern basins. In Middle East, South America, Australia and the the following account, age assignments related to Barents Sea), but has tended to be regional or local these and other schemes reflect those of the original in focus (see Truswell 1980). A number of authors authors but may not necessarily use modern chrono- (Bharadwaj 1969; Kemp 1975; Bharadwaj & Sri- stratigraphic nomenclature, thus a variety of strati- vastava 1977; Balme 1980; Truswell 1980; Utting & graphic stage and other nomenclature is used in Piasecki 1995; Warrington 1996; Price 1997; Play- this paper. For the convenience of the reader, a ford & Dino 2005; Azcuy et al. 2007; Stephenson chart showing correlations of the main chronostrati- 2008a) have attempted to summarize the research or graphic subdivisions used internationally is shown to correlate the main biozones across regions, but in Figure 1. correlation has been tentative. Among the difficul- Permian palynostratigraphic schemes use pollen ties acknowledged by these previous reviewers are and spores almost exclusively. While it is recog- disparate stratigraphic and taxonomic methods nized that marine palynomorphs (acritarchs) may practised in different parts of the world, and differ- be present in Permian rocks, no study has sought ent standards of documentation of palynological data. to produce a palynostratigraphy based purely on StandardRussia Tethys Western Europe China North America Changhsingian ? Changhsingian 254.2 Dorashamian Thuringian ? Wuchiapingian Wuchiapingian ? Dzhulfian Lopingian Late Permian 259.8 Ochoan Capitanian Capitanian Tatarian Midian 265.1 Saxonian Maokouian Wordian Wordian Guadalupian Middle Permian 268.8 Murghabian ? Roadian Kazanian Roadian 272.3 Ufimian Kubergandian Rotliegend Kungurian Kungurian Leonardian Bolorian 279.3 Luodianian Arnskian Arnskian Yakhtashinian Autunian 290.1 Wolfcampian Early Permian Cisuralian Sakmarian Sakmarian Sakmarian 295.5 Chuanshanian Asselian Asselian Asselian 298.9 Fig. 1. Chronostratigraphy of the Permian, modified after Henderson et al. (2012). Downloaded from http://sp.lyellcollection.org/ by guest on October 1, 2021 PERMIAN PALYNOSTRATIGRAPHY Permian acritarchs, although they may show future plant macrofossils differently (Utting & Piasecki potential (e.g. Lei et al. 2013). 1995). Balme (1970), Sullivan (1965), Turnau The range of morphology seen in palynomorphs (1978) and Van der Zwan (1981) surveyed the haz- in the Permian is illustrated simply in Figure 2. ards of the reconstruction of palaeophytogeograph- To improve readability, names of authors of taxa ical provinces by palynology. The value of pollen are excluded from the main text of the paper, but and spore taxa as indices of low-rank plant taxa is the main taxa and their authorship are listed in limited because the plant affinities of most Palaeo- Appendix A. zoic spore and pollen genera and species are unknown, and because botanical and palynological taxonomy are independent of one another. Despite Phytogeography of the Permian this, the broad palynological characteristics of a region at a certain time are thought to be representa- Phytogeographical provinciality makes correlation tive of the high-rank palaeobotanical characteristics difficult because it tends to reduce the number of of that region (Utting & Piasecki 1995). taxa in common between assemblages in different In broad terms, there was a gradual diversifica- provinces. In general, it seems reasonable to expect tion of phytogeographical provinces from relatively geographical parity between palaeobotanical prov- uniform palaeophytogeography