Faunal Migration Into the Late Permian Zechstein Basin – Evidence from Bryozoan Palaeobiogeography ⁎ Anne M
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Palaeogeography, Palaeoclimatology, Palaeoecology 251 (2007) 198–209 www.elsevier.com/locate/palaeo Faunal migration into the Late Permian Zechstein Basin – Evidence from bryozoan palaeobiogeography ⁎ Anne M. Sørensen a, Eckart Håkansson a, Lars Stemmerik a,b, a Department of Geography and Geology, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark b Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark Received 24 October 2006; received in revised form 8 March 2007; accepted 19 March 2007 Abstract Late Permian bryozoans from the Wegener Halvø, Ravnefjeld and Schuchert Formations in East Greenland have been investigated. 14 genera are recognised. Integration of the new bryozoan data from the Upper Permian of East Greenland with data on the distribution of Permian bryozoans along the northern margin of Pangea is used to test hypotheses concerning Late Palaeozoic evolution of the North Atlantic region. During the Permian, the Atlantic rift system formed a seaway between Norway and Greenland from the boreal Barents Shelf to the warm and arid Zechstein Basin. This seaway is considered to be the only marine connection to the Zechstein Basin and therefore the only possible migration route for bryozoans to enter the basin. The distribution of Permian bryozoans is largely in keeping with such a connection from the cool Barents Shelf past the East Greenland Basin to the warm Zechstein Basin and also corroborates the change in temperature through this connection. © 2007 Elsevier B.V. All rights reserved. Keywords: Bryozoans; East Greenland; Palaeobiogeography; Permian; Zechstein Basin 1. Introduction Worsley, 2005). This is in concert with global palaeogeo- graphic reconstructions indicating that Pangaea drifted The Upper Palaeozoic successions of the Sverdrup more than 2500 km northward during this time period, so Basin of Arctic Canada and the North Greenland– that the North Greenland–Norwegian Barents Sea area Svalbard–Norwegian Barents Sea area along the northern moved from c. 20°N latitude in the mid-Carboniferous to c. margin of Pangaea record overall changes in palaeoclimatic 45°N latitude in the Late Permian (Fig. 1; Golonka, 2000; conditions from subtropical and arid in the Late Carbon- Scotese, 2004). The subtropical northern Pangean shelf iferous to temperate in the Late Permian (Beauchamp, was connected south-eastwards to the Tethys Ocean during 1994; Beauchamp and Desrochers, 1997; Stemmerik, Late Carboniferous–Early Permian time, but collision 1997, 2000; Beauchamp and Baud, 2003; Stemmerik and between Laurussia and Siberia during later Permian times apparently disrupted this connection and led to develop- ment of more distinctive Late Permian faunal provinces ⁎ Corresponding author. Present address: Department of Geography and Geology, University of Copenhagen, Øster Voldgade 10, DK-1350 (Fig. 1; Henderson and Mei, 2000). Copenhagen K, Denmark. The Late Permian Zechstein Basin of NW Europe is a E-mail address: [email protected] (L. Stemmerik). marine, partly evaporitic intracratonic basin located at c. 0031-0182/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.palaeo.2007.03.045 A.M. Sørensen et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 251 (2007) 198–209 199 Fig. 1. Late Permian global reconstruction showing the position of the Zechstein Basin (Z), Greenland (G) and Svalbard, and conodont fauna provinces. Based on Golonka (2000) and Henderson and Mei (2000). 20°N palaeolatitude immediately west of the Tethys bryozoan fauna of the Upper Permian carbonates of Ocean (Fig. 1). The lower part of the depositional suc- central East Greenland, located at a palaeolatitude of c. cession is dominated by open marine platform carbo- 32°–35°N, midway between the Boreal cool-water nates and reefs with a rather endemic fauna with carbonate platforms of North Greenland–Norwegian little in common with the Tethyan fauna of the time- Barents Sea and the warm and arid areas of the equivalent successions in the Austrian and Italian Alps Zechstein basin in NW Europe (Stemmerik, 2001). (e.g. Hollingworth and Tucker, 1987; Ernst, 2001a). The sediments and associated fauna form an important This has led to the common belief that the Zechstein link between the Late Permian cool- and warm-water Basin was semi-enclosed, separated by a land barrier carbonate realms, and the East Greenland bryozoans from the Tethys Ocean and connected northwards to the combined with published bryozoan data from North Arctic Boreal Ocean via the rifted seaway between Greenland, Svalbard and the western Tethys provide Greenland and Norway (Fig. 1). To test and further better understanding of Late Permian biogeography and substantiate this hypothesis, we have studied the the faunal migration into the Zechstein Basin. Fig. 2. Correlation of Permian lithostratigraphic units in Spitsbergen, Bjørnøya, North Greenland, East Greenland and the Zechstein Basin. Modified from Stemmerik (2000). 200 A.M. Sørensen et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 251 (2007) 198–209 2. Permian stratigraphy and facies The Permian succession in the Svalbard–Norwegian Barents Sea area belongs to three groups which reflect the Marine Permian deposits are known from outcrops changes in palaeoclimate over time (Fig. 2; Stemmerik, and cores in NW Europe, East Greenland, North Green- 1997; Larssen et al., 2005; Stemmerik and Worsley, land, Svalbard and the offshore areas of the Barents 2005). The Asselian–Sakmarian part of the Gipsdalen Shelf and the mid-Norwegian shelf (Stemmerik, 2000). Group consists mostly of platform carbonates with a Lower Permian marine strata are confined to the North diverse chloro-foramol biota typical of Permian warm- Greenland–Norwegian Barents Sea area in the north water shelf areas (see Beauchamp, 1994). The carbonate whereas marine Upper Permian sediments are known platforms surround deep halite basins thus implying from the entire region. overall warm and arid conditions during Early Permian Fig. 3. Asselian–Kazanian palaeogeographic reconstructions of the western Tethys, Russian Platform, NW Europe and Greenland showing composition of the bryozoan fauna. For numbers, refer to Table 1. Green: land; light blue: shelves; dark blue: oceanic. Note the closure of the strait between the Tethys and the Russian Platform from (A) Asselian to (B) Artinskian time, and the stepwise opening of the seaway between Greenland and Norway during (C) Kungurian–(D) Kazanian time. Palaeogeography modified from Golonka (2000). Fauna data from Ross and Ross (1962, 1990), Malecki (1968, 1977), Southwood (1985, 1990), Madsen and Håkansson (1989), Nakrem (1991, 1993, 1994a,b,c, 2004), Nakrem et al. (1992), Madsen (1994) and Ernst (2000, 2001a, 2003) and our own data in East Greenland. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) A.M. Sørensen et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 251 (2007) 198–209 201 Fig. 3 (continued). times (Stemmerik, 2000; Stemmerik and Worsley, 2005). The Lower–Upper Permian (Kungurian–Wuchiapin- Dating of this part of the succession is based on fusulinids, gian/Changhsingian?) Tempelfjorden Group is dominated and correlation is firmly established internally in the by deeper water spiculites, shales and local sandstones region, including North Greenland, and to the Interna- and cool-water carbonates. Dating is based on small tional zonation (Fig. 2; Dallmann et al., 1999; Stemmerik, foraminifers, palynomorphs and conodonts, and is less 2000; Larssen et al., 2005; Stemmerik and Worsley, 2005; well established than for the older Permian succession and references therein). The Lower Permian (upper (Stemmerik, 2000; Larssen et al., 2005). In North Sakmarian–Artinskian (lowermost Kungurian?)) Bjarme- Greenland, the time-equivalent upper Kim Fjelde and land Group is dominated by temperate cool-water Midnatfjeld formations are composed of cool-water car- carbonates with a bryozoan–brachiopod–echinoderm bonates in the platform areas and shales and spiculites in dominated fauna (Stemmerik, 1997). Dating is based on more distal settings (Stemmerik, 1997). Correlation to the local fusulinid assemblages, conodonts and small for- more southerly located Permian strata of central East aminifers, and correlation to North Greenland and Greenland and the Zechstein basin is still disputed. The adjacent areas is generally well established (see Stem- Wegener Halvø and Ravnefjeld formations of central East merik, 2000). Greenland are of Kazanian (Wuchiapingian) age based on 202 A.M. Sørensen et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 251 (2007) 198–209 Fig. 3 (continued). palynomorphs and conodonts and correlate, based on during several expeditions to East Greenland and was microfloral evidence with the Midnatfjeld Formation of simply chosen with respect to density and preservation North Greenland and the uppermost Tempelfjorden of the bryozoans. It represents both the Wegener Halvø Group of the Norwegian Barents Shelf, and, based on and Schuchert Dal formations and thus spans most of conodonts with the (?) lower part of the Zechstein the Late Permian. All bryozoans are embedded in matrix succession (Fig. 2; Rasmussen et al., 1990; Mangerud, but some samples have bedding planes with large and 1994; Utting and Piasecki, 1995; Stemmerik et al., 1996; well-preserved colonies which were used for external Henderson and Mei, 2000). The overlying Schuchert