Lower Permian Bryozoans from Southern and Central Spitsbergen, Svalbard
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Lower Permian bryozoans from southern and central Spitsbergen, Svalbard HANS ARNE NAKREM, BŁAŻEJ BŁAŻEJOWSKI, and ANDRZEJ GAŹDZICKI Nakrem, H.A., Błażejowski, B., and Gaździcki, A. 2009. Lower Permian bryozoans from southern and central Spits− bergen, Svalbard. Acta Palaeontologica Polonica 54 (4): 677–698. doi:10.4202/app.2008.0078 Bryozoans from the Lower Permian Treskelodden and Wordiekammen formations of southern and central Spitsbergen respectively, Svalbard, have been studied. Twenty species are identified, including one new genus, Toulapora gen. nov., with Toulapora svalbardense as type species and one new species, Ascopora birkenmajeri sp. nov. The taxonomic com− position is typical Lower Permian, with species in common with Timan−Pechora and the Urals (Russia) and Ellesmere Island (the Canadian Arctic). Growth habits reflect a moderately to deeper shelf environment. Key words: Bryozoa, Permian, Spitsbergen, Arctic. Hans Arne Nakrem [[email protected]], University of Oslo, Natural History Museum, PO Box 1172 Blindern, 0318 Oslo, Norway; Błażej Błażejowski [[email protected]] and Andrzej Gaździcki [[email protected]], Instytut Paleobiologii PAN, ul. Twarda 51/55, PL−00−818 Warszawa, Poland. Received 16 October 2008, accepted 1 June 2009, available online 21 August 2009. Introduction by Mari Skaug for a university thesis work in the early 1980s (Skaug 1982), yielded a bryozoan fauna with many compo− The bryozoans described here are from strata representing the nents similar to the Hornsund material. The Tyrrellfjellet two Lower Permian marine formations on Spitsbergen (Sval− Member here – the “Limestone B” – see Skaug (1982: 22) bard): the Treskelodden Formation and Wordiekammen For− and Gee et al. (1953) contains 10–14 fining−upwards se− mation (Figs. 1, 2). quences each 0.5 to 7 m thick. Bioturbation is common, and the carbonate texture varies from mudstone to grainstone, The Treskelodden Formation in the Hornsund area (south with common crinoid and brachiopod grains. Well preserved Spitsbergen) is 120 m thick succession of fossiliferous shal− brachiopods, like Tornquistia forbesi (Gobbett 1963) and low−marine clastic sediments deposited under relatively dy− Cancrinella singletoni Gobbett 1963 are locally common namic−water conditions on the continental shelf, as indicated (Skaug 1982), often in life position. Other brachiopods are by palaeontological and sedimentological data (Birkenmajer present with their spines preserved. The depositional envi− 1979, 1984; Fedorowski 1982; see also Dallmann 1999). ronment is considered to reflect near−shore migrating car− The studies of foraminifers and bryozoans were carried bonate shoal sands outside more lagunal settings. out using thin sections from samples collected through the The Gipsvika material is well dated by fusulinaceans Treskelen and Hyrnefjellet sections (Figs. 3, 4). (Nilsson 1988, 1993) and conodonts (Nakrem et al. 1992). Foraminiferal assemblages consisting of 23 genera and 58 A rich bryozoan fauna from this area was described by species were recovered in the formation and three biostrati− Nakrem (1994a) and some material from that publication has graphical assemblage zones: Pseudofusulinella occidentalis, been re−investigated in the current work. Midiella ovata–Calcitornella heathi,andHemigordius arcti− The bryozoans from the Treskelodden Formation were cus–Hemigordius hyrnensis were recognised for regional and collected in 1997 by AG and Andrzej Kaim and in 2005 by interregional correlation (Błażejowski 2008, 2009). BB and AG. Detailed taxonomic and stratigraphic analysis of fora− minifers dated the Treskelodden Formation as Gzhelian– Institutional abbreviations.—PMO, palaeontological collec− Artinskian (Błażejowski et al. 2006; Błażejowski and Gaź− tion Natural History Museum, University of Oslo, Norway; dzicki 2007; Błażejowski 2009). ZPAL, Institute of Paleobiology, Polish Academy of Sci− Additional material from the time−equivalent Wordie− ences, Warsaw, Poland. kammen Formation of central Spitsbergen has also been pre− Other abbreviations.—CV, coefficient of variation (SD*100/ pared for the current study to aid identification of bryozoan X); MAX, maximal value; MIN, minimal value; N, number species. The Gipsvika section (Figs. 1, 2), inner Isfjorden of zoaria measured; n, number of measurements taken; SD, area (Asselian–Sakmarian, Tyrrellfjellet Member), sampled sample standard deviation; X, mean value. Acta Palaeontol. Pol. 54 (4): 677–698, 2009 doi:10.4202/app.2008.0078 678 ACTA PALAEONTOLOGICA POLONICA 54 (4), 2009 Fig. 1. Map of Svalbard with localities mentioned in the text. International Correlation Central Spitsbergen Inner Hornsund Ogg et al. (2008) Material and methods ?Kazanian The majority of information used in this study comes from Kapp Starostin Kapp Starostin - field observations and descriptions of two outcrop localities, Fm. Fm. Ufimian Hyrnefjellet and Treskelen, representing approximately Guadalupian 150 m of strata, along the fjord Hornsund. More than 50 sam− Kungurian Tempelfjorden Group ???? ples were collected for laboratory examination. Stratigraphic Gipshuken Fm. ???? Artinskian Permian placement of samples is indicated in Figs. 3 and 4 (litho− Sakmarian stratigraphic logs for Treskelen and Hyrnefjellet); these sam− Tyrrellfjellet Mbr. Cisuralian ple numbers are also used in the systematic description of in− Treskelodden Fm. Wordie- Asselian dividual taxa. Samples Br.12/G14–G16 are scree samples kammen Fm. (loose material) from Hyrnefjellet. Kapitol/Cadellfjellet Mbr. Gzhelian Bryozoans were identified from standard petrographic Kasimovian thin sections, in many cases not providing the desired orien− Gipsdalen Group Minkinfjellet Fm. Hyrnefjellet Fm. Moscovian tations for proper bryozoan identification. Some samples were subsequently thin sectioned in Oslo to obtain oriented Carboniferous views of the bryozoans. 46 thin sections were made from these samples. Acetate peels were made initially from most Fig. 2. Lithostratigraphy of Hornsund area and inner Isfjorden area (emended samples, but did not always give enough details due to partly from Dallmann 1999). silicification of the fossil contents. NAKREM ET AL.—LOWER PERMIAN BRYOZOANS FROM SPITSBERGEN 679 Samples from Gipsvika were thin−sectioned after prepa− Fistuliporidae indet. ration of acetate peels revealed problematic dolomitisation Fig. 5A–C. and silicification of some of the bryozoans. 73 oriented thin Material examined sections were made from a carbonate rich interval with visi− .—Treskelen, sample ZPAL Br. 12/Cr. ble, but rock embedded bryozoans. 55, PMO 170.908A−D. Remarks.—Varying parts of encrusting zoaria of Fistulipora− like bryozoans were observed in several thin sections. Mor− phological characters include short tubular autozooecia bud− Bryozoan distribution ding from substrate and bending at their bases towards the col− ony surface, slightly oval apertures with well developed luna− Treskelen.—The lowermost part of the Treskelen section ria, and small vesicles arranged usually in 2–3 rows between (see Fig. 3) contains only two bryozoans identifiable to spe− autozooecia. Due to insufficient material a more precise iden− cies level, Rectifenestella submicroporata and a species tification cannot be presented. questionably identified as Rhombotrypella cf. arbuscula. The former species has an Asselian distribution in Russia, whereas the latter has a younger Artinskian–Kungurian dis− Family Hexagonellidae Crockford, 1947 tribution. Slightly higher in the same section Sakmarian Genus Coscinium Keyserling, 1846 species like Coscinium cyclops and Ascopora sterlitama− Type species: Coscinium cyclops Keyserling, 1846, Early Permian of kensis are present. The bryozoans in general support the Timan, Russia. biostratigraphic dating for this unit based on small fora− Coscinium cyclops Keyserling, 1846 miniferans (Błażejowski 2008). Figs. 6A–E, 8A, 10H. Hyrnefjellet.—As for the Treskelen section, Sakmarian spe− Material examined.—Measurements based on 10 zoaria in cies like Coscinium cyclops and Ascopora sterlitamakensis the following samples: Hyrnefjellet (scree), thin sections are present in lower part of the Hyrnefjellet section. These PMO 170.892A−B, as well as 11 thin sections from samples bryozoans support the biostratigraphic dating for this part ZPAL Br. 12/H10, G16; Treskelen, sample ZPAL Br. 12/Cr. based on small foraminiferans. Ascopora magniseptata, 55, thin section PMO 170.908B and one thin section ZPAL occurring near the Sakmarian–Artinskian transition in the Br. 12/Cr. 55; Gipsvika, thin sections PMO 170.919A−G. Hyrnefjellet section has a Gzhelian distribution in its type Description.—Bifoliate frondescent colonies with oval and area in the Urals, and thus has a significantly younger distri− circular fenestrules and anastomosing branches with zooecia bution in Svalbard. opening on both sides of branches. The branches are lens− Gipsvika.—The bryozoans identified from the Gipsvika sec− shaped in cross section being bifoliate compressed perpen− tion have a general Sakmarian affinity. Coscinium cyclops has dicular to branch surfaces. Width of branches varies between its first appearance in the late Asselian (Nenets Horizon), but 2.86 and 3.00 mm, thickness 1.53–2.51 mm. The fenestrules is more common in the Sakmarian–Artinskian (Komichan are 2.00–2.81 mm long and 1.66–1.92 mm wide. Vesicular, Horizon) of Timan−Pechora and the Urals (Morozova and blister−like tissue is developed between autozooecial tubes. Kruchinina 1986). Ascopora grandis and Ascopora