Carboniferous palynoevents in the circum-Arctic region GUNN MANGERUD1*, GILDA LOPES2 and JONATHAN BUJAK3 1. Department of Earth Science, University of Bergen, Allégaten 41, N-5007 Bergen, Norway 2. University of Algarve, Centre for Marine and Environmental Research, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal 3. Bujak Research (International), 114 Abbotsford Road, Blackpool, Lancashire FY3 9RY, UK *Corresponding author <[email protected]> Date received: 4 November 2019 ¶ Date accepted: 24 June 2020 ABSTRACT The Carboniferous of the present-day Arctic yields an abundant and diverse association of terrestrial palynomorphs, particularly from Mississippian successions. Relatively few sections have been studied. However, those published so far demonstrate considerable similarities in the palynofloras between Arctic regions. Based on the published record, we present a compilation of 31 last occurrences (LOs), first occurrences (FOs), and some abundance events that have correlation potential around the Arctic. The chronostratigraphic resolution is relatively low, and the lack of independent age control hampers exact age assignments. But for most of these successions, palynology is the only dating tool available. RÉSUMÉ Le Carbonifère de la région arctique d’aujourd’hui fait état d’une association abondante et diversifiée de palynomorphes terrestres, en particulier de successions du Mississippien. Relativement peu de sections ont été étudiées. Celles publiées jusqu’ici montrent toutefois des similarités considérables des palynoflores entre les régions arctiques. En nous basant sur les documents publiés, nous présentons une compilation des 31 dernières occurrences (DO), des premières occurrences (PO) et de certains phénomènes d’abondance qui pourraient être corrélés dans la région de l’Arctique. La résolution chronostratigraphique est relativement faible et l’absence de critères de datation gêne l’attribution d’âges exacts. La palynologie constitue toutefois le seul outil de datation disponible dans le cas de la majorité de ces successions. [Traduit par la redaction] INTRODUCTION recorded in Carboniferous strata, palynology is a critical tool for dating and refining the stratigraphic correlations of This article is a contribution to the Circum-Arctic rocks of that period. This is particularly true for the Mis- Palynological Events (CAPE) project, providing a scheme sissippian, a time during which non-marine clastics were of selected events for the Carboniferous in the present- the dominant deposits, a result of rifting in a series of local day Arctic. The Carboniferous Period extended from 358.9 half-grabens in most Arctic areas. Carboniferous palyno- to 298.9 Ma according to Gradstein et al. (2020). The morphs are therefore dominantly miospores deposited in Carboniferous is divided into two subperiods, Mississip- fluvial and lacustrine sediments, although freshwater algae pian and Pennsylvanian, the latter having a base at 323.2 Ma. are sometimes abundant, and rare scolecodonts and marine The Mississippian is divided into Tournaisian, Visean and acritarchs occur in the Visean. Palynological data is sparser Serpukhovian stages, and the Pennsylvanian is divided into for the Pennsylvanian successions in the Arctic, at a time the Bashkirian, Moscovian, Kasimovian and Gzhelian when carbonate deposition dominated due to the shiftfrom stages. Historically, various chronostratigraphic schemes have humid to arid climatic conditions and ongoing sea-level rise. been applied to the Carboniferous, making correlation and The present Carboniferous compilation will be added comparison between the various palynological zonations to others from the CAPE Special Issue of Atlantic Geology, and charts difficult. However, as a “rule of thumb”, the prev- which will contribute ultimately (when all articles in the ious use of Lower and Upper Carboniferous may be replaced issue are complete) to the “CAPE datapack” in Time Scale by Mississippian and Pennsylvanian respectively, although Creator (TSC; https://timescalecreator.org/index/index. the latter might include the latest Mississippian in some cases. php) and thus can be used with other data in TSC make As palynomorphs are the most common fossil group plots such as that shown in Fig. 1. Figure 1 includes the age ATLANTIC GEOLOGY 56, 41–55 (2021) doi:10.4138/atlgeol.2021.003 0843-5561|21|0041–0055$3.25|0 ATLANTIC GEOLOGY · VOLUME 57 · 2021 42 Carboniferous palynomorph events (GTS2020) Marine Macrofossils (Mesozoic-Paleozoic) Standard Chronostratigraphy Geomagnetic Paleozoic Ammonoids Polarity Ma Period Epoch Age/Stage Substage Major Paleozoic ammonoid markers Carboniferous Arctic palynomorph events (this paper) 299 Kartam Pa12 yshian Shumardites 300 N 301 Gzhelian Shumardites / Vidrioceras Pa11 302 Late Penn. 303 Vidrioceras / Artinskia Abundant monosaccate pollen 304 Dunbarites - 305 Kasimovian Pa10 Parashumardites 306 Parashumardites Vittatina spp. 307 Pa9 Eoschistoceras 308 Microreticulatisporites nobilis 309 Pa8 Pseudoparalegoceras Lundbladispora gigantea 310 Middle Penn. Moscovian 311 312 Paralegoceras / Pa7 Eowellerites 313 Eowellerites Cadiaspora magna, Columnisporites heyleri, Diaboloceras - Microreticulatisporites nobilis, Punctatisporites 314 Pa6 Winslowoceras Winslowoceras sinuatus, Thymospora spp. 315 Pa5 Diaboloceras - Axinolobus 316 317 N8? Branneroceras / Pa4 318 Gastrioceras Florinites spp. (consistent) N7? 319 Early Penn. Bashkirian Pa3 Bilinguites / Cancelloceras 320 321 Baschkortoceras / Pa2 Reticuloceras 322 Reticuloceras N5 Pa1 Homoceras / Hudsonoceras 323 Inferred Homoceras GAP Tripartities vetustus (rare) 324 N2? 325 Delepinoceras / Cravenoceras Ma9 326 Fayettevillea 327 Late Miss. Serpukhovian 328 Florinites spp. (sporadic), Potonieisporites Cravenoceras / Goniatites elegans N1? Ma8 Uralopronorites Eumorphoceras 329 Carboniferous Triquitrites marginatus Raistrickia nigra (rare) 330 331 Potoneispores delicatus Hypergoniatites / 332 Ma7 Ferganoceras Tripartities vetustus (rare) Corbulispora cancellata 333 Cingulizonatus bialatus, Spelaeotriletes arenaceus (rare), Waltziaspora planiangulata 334 Cingulizonates flammulus 335 336 Cristatisporites bellus (rare) 337 Diatomozonotriletes saetosus 338 Schulzospora spp. 339 Middle Miss. Visean 340 Lycospora pusilla Ma6 Beyrichoceras / Goniatites 341 342 343 344 345 Goniatites 346 347 Fascipericyclus / Legend Ma5 Ammonellipsites 348 First occurence Dzhaprakoceras 349 Last occurence 350 351 Ma4 Protocanites / Pericyclus 352 Pericyclus 353 Early Miss. Tournaisian 354 Ma3 Protocanites / Gattendorfia Potoneispores delicatus 355 356 Pustulatisporites gibberosus, Stenozonotriletes Ma2 Eocanites / Gattendorfia 357 clarus, Vallatisporites banffensis, Vallatisporites vallatus 358 Ma1 Acutimitoceras Mangerud et al. – Carboniferous palynoevents in the circum-Arctic region ATLANTIC GEOLOGY · VOLUME 57 · 2021 43 calibration in millions of years (Ma) according to the 2020 Kasimovian age and the Potonieisporites spp. – Vittatina sp. version of TSC. Assemblage Zone of Gzhelian – Asselian of earliest Permian The events compiled herein include last occurrences age. The zones were based on outcrop and subsurface sam- (LOs), first occurrences (FOs), and some abundance events. ples and were collected from strata in which marine faunas Where possible, each event is correlated with the base of a provided some independent age control. However, neither chronostratigraphic unit, for example an ammonoid zone a range chart nor plates were provided. From the Emma or a formal stage. If the event is not equivalent to the base Fiord Formation in the Sverdrup Basin, Utting et al. (1989b) of such a unit, then an estimation is given as a percentage recorded well-preserved assemblages and presented range above the base of the chronostratigraphic unit relative to charts, plates and lists of taxa, as well as correlations, and the entire unit. Details of how a biostratigraphic datapack indicated which taxa that they considered to be of strati- is constructed in TSC from such information are given in graphic importance. Bringué et al. (in press). Localities used for the present com- Utting (1991) examined 21 outcrops from the Mississip- pilation are shown in Fig. 2. Figure 3 gives a summary of pian Hart River Formation of northern Yukon. From these zonation schemes discussed in the following section he recorded 32 genera and 44 species. He presented two and referenced in the Palynoevents section. informal zones: the Murospora aurita – Rotaspora fracta Assemblage Zone of Visean age and the Potonieisporites ele- gans Assemblage Zone of early Serpukhovian age. PALYNOSTRATIGRAPHY From the Northwest Territories (former District of Mack- enzie) and Yukon, Braman and Hills (1992) defined the Mis- The events compiled herein include last appearance da- sissippian Vallatisporites banffensis – Vallatisporites vallatus tums (LOs), first appearance datums (FOs), and some Biozone from outcrop sections in the Tuttle Formation. abundance events. Their relationship to other fossil zonal They had no independent age control, but the Biozone is schemes (Fig.2) is shown in the TSC plot (Fig. 3). Despite a above the LO of Retispora lepidophyta, which is close to the re-evaluation by Ogg et al. (2016), the Devonian/Carbonif- Devonian/Carboniferous boundary, so they regarded the erous boundary is currently formally identified by the first Biozone as Tournaisian. appearance of the conodont Siphonodella sulcata, which From the Alaskan North Slope, Ravn (1991) presented appears