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Bohemian-type Silurian (Telychian) bivalves from Arctic Russia a
a
Olga K. Bogolepova , Alexander P. Gubanov & Victoria L. Pease
b
a
Department of Earth Sciences, Uppsala University, Villavägen 16, SE-752 36, Uppsala, Sweden E-mail:
[email protected] b
Department of Geology & Geochemistry, Stockholm University, SE-106 91, Stockholm, Sweden Available online: 06 Aug 2009
To cite this article: Olga K. Bogolepova, Alexander P. Gubanov & Victoria L. Pease (2005): Bohemian-type Silurian (Telychian) bivalves from Arctic Russia, GFF, 127:4, 247-252 To link to this article: http://dx.doi.org/10.1080/11035890501274247
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GFF volume 127 (2005), pp. 247–252.
Article
Bohemian-type Silurian (Telychian) bivalves from Arctic Russia OLGA K. BOGOLEPOVA1, ALEXANDER P. GUBANOV1 and VICTORIA L. PEASE2 Bogolepova, O.K., Gubanov, A.P. & Pease, V.L., 2005: Bohemian-type Silurian (Telychian) bivalves from Arctic Russia. GFF, Vol. 127 (Pt. 4, December), pp. 247–252. Stockholm. ISSN 1103-5897.
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Abstract: The Bivalvia genera Ctenodonta, Dualina? and Sibirinka have been identified from the Silurian Telychian Stage, Llandovery Series of Severnaya Zemlya, Arctic Russia. This is the second record of the earliest epibyssate pteriomorphs previously reported from Siberia; they flourished later in the basins of central and southern Europe. Their distribution is consistent with surface ocean currents carrying abundant cephalopods, whose accumulation on the bottom surface together with ocean current activity represented a favourable environment for epibyssate bivalves. Keywords: Bivalvia, palaeontology, palaeogeography, Silurian, Telychian, Severnaya Zemlya, Arctic Russia. Department of Earth Sciences, Uppsala University, Villavägen 16, SE-752 36, Uppsala, Sweden;
[email protected] 2 Department of Geology & Geochemistry, Stockholm University, SE-106 91, Stockholm, Sweden Manuscript received 28 January 2005. Revised manuscript received 17 May 2005. Revised manuscript accepted 1 November 2005. 1
Introduction
The Silurian bivalves from the Severnaya Zemlya Archipelago of northern Russia are little known. Markovsky & Smirnova (1982) reported bivalves from the uppermost part of the Silurian succession of this area, however, none of these fossils were described or illustrated. This paper reports on early Silurian bivalves collected during an expedition to the Severnaya Zemlya Archipelago in 1999 (Gee et al. 1999). All the figured specimens are deposited at the Museum of Evolution, Uppsala University, Sweden (PMU SZ 5-7).
Geological Outline
The islands of the Severnaya Zemlya Archipelago, formerly Tsar Nicholas II Land, are located in the Kara Sea, north of the Taimyr Peninsula of central Siberia (Fig. 1). A rich Palaeozoic fauna was reported from this area about 70 years ago, when the first expeditions (Urvantsev 1933) started to explore the territory. Subsequently, during the geological mapping of the region (Egiazarov 1970), particular attention was devoted to palaeontology and stratigraphy. Together with northern Taimyr, Severnaya Zemlya belongs to the North Kara plate (Bogdanov et al. 1998), or a terrane with a pre-Riphean basement and an Upper Proterozoic and Lower to Upper Palaeozoic sedimentary cover. The oldest rocks are of flyschoid character and are late Riphean in age. They are overlain by a marine Cambrian to Devonian succession which terminates in Upper Devonian strata of continental facies. The Silurian of the Severnaya Zemlya Archipelago comprises a succession dominated by shallow-water carbonates, and thin interbeds of sandstones, ranging in age from middle Llandovery to Pfiídolí. These deposits are up to 2500 m thick. They are richly
fossiliferous and yield a diverse fauna of tabulate and rugose corals, stromatoporoids, crinoids, brachiopods, ostracodes, gastropods, cephalopods, bivalves, bryozoans and vertebrates. The detailed stratigraphy is described and discussed in Menner et al. (1979), Klubov et al. (1980), Markovsky & Smirnova (1982) and Kurik et al. (1982). Revised biostratigraphies have been published recently by Matukhin et al. (1999), Bogolepova et al. (2000) and Männik et al. (2002). During the Silurian Period, the North Kara Terrane was located at low latitudes, which is strongly supported by lithic and faunal evidence (Matukhin et al. 1999; Siveter & Bogolepova in press), as well as by preliminary palaeomagnetic data (Metelkin et al. 2000). It was apparently separate from Siberia, Baltica and Laurentia. It should be mentioned, however, that the early Palaeozoic history of the North Kara Terrane has been widely discussed and different interpretations have been proposed (Zonenshain & Natapov 1987; Zonenshain et al. 1991; Gee 1996; Vernikovsky 1997).
Stratigraphy and localities
All the specimens discussed in this paper originate from the Lower Silurian Sredninskaya Formation. These rocks were previously referred to as part of the Golomyannaya Formation (Menner et al. 1979; Bogolepova et al. 2000). The formation is composed of irregular thin-bedded limestones with alternating dolomites and calcareous dolomites and occasional layers (0.1-1 m) of quartz sandstones and siltstones. Limestones are dolomitised, greenish-grey and grey. Stromatolitic and microphytolitic limestones are present, but subordinate. The unit is at least 120 m thick at its type locality, but is thinner elsewhere.
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Fig. 1. Generalised map of the Severnaya Zemlya Archipelago showing location of section BG99-13, Ushakova River, October Revolution Island and the bivalve-bearing part of the Sredninskaya Formation, Llandovery, Silurian.
The new material comes from locality BG99-13 (N 79º40ʼ28ʼʼ; E 96º31ʼ10ʼʼ) exposed in the middle reaches of the Ushakova River in the central part of October Revolution Island. Here, a thin sequence (
