Faunal Migration Into the Late Permian Zechstein Basin – Evidence from Bryozoan Palaeobiogeography ⁎ Anne M

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 palaeogeographic 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 development 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 Dal investigations. The internal characteristics were studied Formation is of Changsingian age and may correlate to the in acetate peels made from polished surfaces. uppermost Zechstein of NW Europe (Fig. 2). Data in Ross and Ross (1962, 1990), Malecki (1968, 1977), Southwood (1985, 1990), Madsen and Håkans- 3. Material and methods son (1989), Nakrem (1991, 1993, 1994a,b,c, 2004), Nakrem et al. (1992), Madsen (1994) and Ernst (2000, The investigated material from East Greenland was 2001a, 2003) on Permian bryozoans from Svalbard, selected among a large collection of samples collected North Greenland, the Russian Platform, the Zechstein A.M. Sørensen et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 251 (2007) 198–209 203

Fig. 3 (continued).

Basin and the Tethys area were, together with our own below; a taxonomic list covering the East Greenland fauna data from East Greenland treated with multivariate is found in Fig. 6. statistical analysis; i.e. detrended correspondence analysis (DCA) and cluster analysis (Raup–Crick's coeffi- 3.1. Tethys bryozoan fauna cient of similarity) in order to reveal possible trends in their distribution (Figs. 3–5). The Asselian and The shelf areas surrounding the tropical Tethys Kazanian fauna from the western Central Tethys have Ocean contained a highly diverse bryozoan fauna. In been included as out-groups in the analyses. this study, we have limited the data set to include only The analyses were made on the program PAST the western Central platforms of the Carnian Alps and (PAleontological STatistics) and were based on binary Transcaucasus since these areas were located adjacent to (present/absent) data. We have focussed on four time the Early–Late Permian Russian Platform and the Late slices corresponding to the Asselian, Artinskian and Permian Zechstein Basin. From this part of the Tethys, a Kungurian stages, as well as the Kazanian which here is total of 72 Permian genera have been listed by Ross and regarded as roughly equivalent to the Wuchiapingian. The Ross (1990) and Ernst (2000, 2003). The highest data sets used for these analyses are briefly summarised diversity is in the Kazanian succession from where 53 204 A.M. Sørensen et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 251 (2007) 198–209

Fig. 4. Cluster analysis of the Permian bryozoan fauna in the study area based on data in Ross and Ross (1962, 1990), Malecki (1968, 1977), Southwood (1985, 1990), Madsen and Håkansson (1989), Nakrem (1991, 1993, 1994b,c, 2004), Nakrem et al. (1992), Madsen (1994) and Ernst (2000, 2001a, 2003) and our own data from East Greenland. For colour codes, see Fig. 5. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) genera have been identified compared to 28 genera genera in the Asselian, 25 in the Artinskian, 17 in the in the Kungurian, 39 genera in the Artinskian and 29 Kungurian and 23 in the Kazanian. Taxa in common genera in the Asselian. Taxa in common with Svalbard, with Svalbard, Greenland, the western Tethys and the Greenland, the Russian Platform and the Zechstein Zechstein Basin are listed in Fig. 3; for a complete fauna Basin are listed in Fig. 3; for complete fauna lists consult list consult Ross and Ross (1990). Ross and Ross (1990) and Ernst (2000, 2003). The Early Permian Tethys fauna shows great simi- 3.3. Svalbard bryozoan fauna larities with that of the Russian Platform whereas the Late Permian fauna is related more to those found in The Permian bryozoan fauna from Svalbard was de- Asia and Australia (Ernst 2000). In the multivariate scribed and documented by Nakrem (1991, 1993, 1994a, statistical analysis, we have focussed on the Asselian b,c, 2004), Nakrem et al. (1992) and Malecki (1968, and the Kazanian faunas to illustrate connections to the 1977), subsequently revised by Nakrem (1988).The adjacent areas (Figs. 4 and 5). described faunas represent both the Asselian–Sakmarian warm-water carbonate succession and the cool-water 3.2. Russian platform bryozoan fauna carbonates of the Kungurian–Kazanian Tempelfjoden Group. Data on Permian bryozoan distribution on the Russian A total of 50 genera have been described from the Platform are taken from Ross and Ross (1990) who Permian of Svalbard. The fauna of the Asselian suc- recorded a total of 53 Permian genera. They report 34 cession, represented by the Tyrellfjellet Member and the A.M. Sørensen et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 251 (2007) 198–209 205

The fauna thus represents a cool-water carbonate succession of the same age as the Tempelfjoden Group of Svalbard (Fig. 2). So far 22 genera have been recognized from North Greenland, but the bryozoan fauna has not

Fig. 5. DCA analysis of the Permian bryozoan fauna in the study area based on data in 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 from East Greenland. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Kapp Duner Formation, comprises 21 genera with a dominance of robust ramose colonies of Ascoporella and Tabulipora together with delicate fenestrate colonies and fine branched Ascopora and Rhabdomeson colonies (Fig. 3). This fauna has a general affinity to bryozoan faunas from Russia (Nakrem, 1994b). The Artinskian fauna, represented by the upper Artinskian Vøringen Member and Hambergfjelet Formation, comprises 27 genera and is dominated by encrusting and robust trepostomes and cystoporates and by robust fenestrate colonies in coarser beds. The fauna is regarded as Boreal and has affinities to Artinskian reef faunas from the Urals (Nakrem, 1994c). The Kungurian– Kazanian bryozoan faunas are the most diverse of the Permian faunas reported from Svalbard with 35 and 34 genera, respectively (Fig. 3). The faunas are dominated by delicate, ramose Rhombotrypella, Dyscritella and Streblascopora together with delicate fenestrate colonies (Table 1).

3.4. North Greenland bryozoan fauna

The bryozoan faunas described and documented by Ross and Ross (1962), Madsen and Håkansson (1989) and Madsen (1994) from the Permian of North Green- – Fig. 6. Distribution of the Kazanian bryozoan taxa in the North land mainly come from the upper Artinskian Kungur- Atlantic realm. It is assumed that genera occurring both in the northern ian Kim Fjelde Formation with some additional area and in the Zechstein Basin also are present in East Greenland but information from the Kazanian Midnatfjeld Formation. have yet to be found. 206 A.M. Sørensen et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 251 (2007) 198–209

Table 1 Permian bryozoan genera from the study area Trepostomata Fenestrata Cryptostomata Cystoporata Cyclostomata 1 Amphiporella 13 Acanthocladia 38 Ascopora 50 Coscinium 58 Corynotrypa 2 Anisotrypella 14 Alternifenestella 39 Ascoporella 51 Cyclotrypa 3 Dyscritella 15 Archimedes 40 Clausotrypa 52 Eridopora 4 Dyscritellina 16 Fabifenestella 41 Gilmoropora 53 Fistulipora 5 Hinaclema 17 Fenestella 42 Girtyporina 54 Goniocladia 6 Neoeridotrypella 18 Fenestrellina 43 Permoheloclema 55 Meekopora 7 Paralioclema 19 Flexifenestella 44 Primorella 56 Ramipora 8 Rhombotrypella 20 Kalvariella 45 Rhabdomeson 57 Ramiporidra 9 Stellahexaformis 21 Kingopora 46 Rhombopora 10 Stenopora 22 Laxifenestella 47 Streblascopora 11 Tabulipora 23 Lyrocladia 48 Streblotrypa 12 Ulrichotrypa 24 Lyropora 49 Timanodictya 25 Lyroporella 26 Penniretepora 27 Polypora 28 Polyporella 29 Protoretepora 30 Ptylopora 31 Rectifenestella 32 Reteporidra 33 Ryhopora 34 Septopora 35 Spinofenestella 36 Synocladia 37 Wjatkella For numbers, refer to Fig. 3. 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. been investigated in the same detail as that in Svalbard and includes the only confirmed Cyclostomata in the and the Zechstein Basin. study area (Fig. 3). The bryozoans are important reef The fauna of the upper Artinskian part of the Kim builders and are associated with typical warm-water Fjelde Formation comprises 17 genera, of which 13 carbonates, like oolites, and evaporites. genera also are known from the time equivalent suc- One genus Ryhopora is endemic to the Zechstein cession in Svalbard (Fig. 3). The Kungurian fauna is Basin, five genera are known from East Greenland, five slightly more diverse, including two more cryptostome from North Greenland and seven genera are in common genera and one more cystoporate genus (Fig. 3). The Kim with Svalbard. 5 of the 13 Zechstein genera are also known Fjelde Formation is dominated by Tabulipora,further- from Kazanian-age sediments in the western Tethys more Rhombotrypella, Dyscritella and Amphiporella are Sea. Four genera Dyscritella, Stenopora, Fenestella and numerous. The fauna from the Kazanian Midnatfjeld Penniretepora have a very wide geographical distribution Formation includes 18 genera, of which 13 are known being known from Svalbard, Greenland, Zechstein Basin from Svalbard and 7 are from East Greenland (Figs. 3 and western Tethys (Figs. 3 and 6). Five of the Zechstein and 6). The formation is dominated by Tabulipora, genera have not been reported from any of the immediate Fenestella, Polypora and Ramipora. adjacent areas.

3.5. Zechstein bryozoan fauna 3.6. East Greenland bryozoan fauna

The bryozoan fauna from the Zechstein Basin has The East Greenland bryozoan fauna occur in carbon- been described and documented by Southwood (1985, ates of mixed cool- and warm-water affinity midway 1990) and Ernst (2001a). The bryozoan fauna includes between the Late Permian Arctic Boreal Ocean of North 13 genera that are primarily described from the German Greenland, Svalbard and the Barents Sea and the low and English part of the basin. The fauna completely latitude Zechstein Basin (Stemmerik, 2001). Bryozoans lacks members of the Cryptostomata and Cystoporata, are important reef builders in the Kazanian Wegener A.M. Sørensen et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 251 (2007) 198–209 207

Halvø Formation where they occur associated with common with the bryozoan faunas from the Russian typical warm-water carbonate facies like oolites. Platform, northern Pangaea and the Zechstein Basin. The 14 genera have been described and in addition a highest degree of similarity between the western Tethys number of fenestellid taxa related to the genus Fenestella and the Russian Platform is found in the Early Permian, have been found but not identified. The fauna is domi- which is in accordance with the notion that there was a nated by the genera Tabulipora followed in frequency by connection from the North Greenland–Svalbard area Ramipora. Dyscritella, Permoheloclema, Polypora across the Russian Platform to the Tethys Ocean during and the colonies related to Fenestella are also common. this time (Fig. 3A). However, the statistical analyses also Tabulipora also dominates in the time-equivalent indicate that even during this period of open marine Midnatfjeld Formation of North Greenland where also connections from the Tethys to the north slope of Pangea Ramipora, Polypora and Fenestella are common, and three rather different bryozoan faunas co-existed during dominance of Tabulipora and Ramipora also charac- the Early Permian in western Tethys, Russian Platform terises the Svalbard fauna. and along the northern margin of Pangea, respectively. 13 of the East Greenland genera are also known from This most likely reflects the transition from tropical the Permian successions of Svalbard and 5 genera are in conditions in the Tethys area to warm-water, subtropical common with the Zechstein succession. conditions in the Barents Sea area. The almost complete A taxonomic description of the East Greenland fauna is lack of similarity between the Tethyan fauna and Russian under preparation (Sørensen, Håkansson and Stemmerik). Platform fauna in the Kazanian offers additional support to a mid-Permian closure of the migration route fol- 4. Discussion lowing the collision between Siberia and Laurussia. The very high degree of similarity with the Sakmarian The cluster analysis based on Raup-Crick's coefficient fauna of Svalbard and the younger, Artinskian–Kaza- of similarity shows that the Late Permian (Kazanian) nian bryozoan faunas of Svalbard and North Greenland western Tethys bryozoan fauna has little in common with suggests little evolution of the northern Pangean fauna the Early Permian (Asselian) western Tethys fauna following initial migration into the region during the (similarity index close to 0.6), and that the two Tethys Late Carboniferous–Early Permian. This is somewhat faunas deviate significantly (b0.25) from all other surprising, since facies and fauna analyses indicate pro- investigated faunas (Fig. 4). The Permian bryozoan nounced shifts in depositional conditions of the northern faunas in Svalbard, North Greenland and East Greenland Pangaean shelf from warm, subtropical in the Asselian– show high levels of similarity (all N0.95) and as a group Artinskian to cool-water, temperate in the Kungurian– they have a similarity index at the 0.7 level to the Kazanian (Stemmerik, 1997). The stability of the Zechstein Basin bryozoan fauna (Fig. 4). The Early northern Pangaean bryozoan fauna is also in contrast to Permian faunas of the Russian Platform are essentially the pronounced evolution seen both on the Russian identical (N0.99), whereas the Kazanian fauna differs Platform and in the Tethyan Ocean during the Permian. significantly from all other investigated faunas (Fig. 4). The results of the statistical analyses reveal that the The combination of the results of the cluster analysis with East Greenland bryozoan fauna is related more to the those of the DCA analysis indicates that the investigated northern faunas in Svalbard and North Greenland than to bryozoan faunas may be separated into five distinct the Zechstein Basin bryozoan fauna. Thus southwards groups (Figs. 4 and 5). The two Tethyan faunas form a migration of the northern Pangaean bryozoan fauna along fairly tight group in spite of their difference in age; the the evolving North Atlantic rifted seaway was clearly northern Pangaean faunas, including East Greenland, facilitated, at least as far south as central East Greenland form a second distinctive group; while the Early Permian (Figs. 3–5). However, the Zechstein Basin fauna, faunas of the Russian Platform form a third, well-defined although constituting a distinctive group by itself in the group. In addition two faunas are sufficiently different statistical analyses, has a much greater similarity to the from all others to warrant the separation of two single northern Pangaean faunas than to any of the western fauna groups: the Zechstein Basin fauna, which has a Tethys faunas, thus supporting a model where migration much higher degree of similarity to the northern Pangaean continued into the Zechstein Basin, albeit. Of the 13 faunas than to the Tethyan faunas, and the Kazanian fauna genera described from the Zechstein Basin four are in of the Russian Platform, which shows the highest resem- common for all the studied faunas and seem to be cosmo- blance to the Kazanian faunas from Greenland (Fig. 5). politan, and these four are the only genera shared between The combined results of the cluster and DCA analysis the Kazanian fauna of the western Tethys platforms and indicate that the Tethyan faunas in general have little in the Zechstein Basin. In contrast, the Zechstein Basin 208 A.M. Sørensen et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 251 (2007) 198–209 fauna shares three additional genera with the well-studied evolution was more evident, possibly as a result of more Kazanian fauna of Svalbard in addition to one more genus pronounced temperature and salinity gradients. In shared with the less well-known Kazanian faunas of East concord with Ernst (2001b), our analyses rule out the and North Greenland (Figs. 3 and 6). This pattern of possibility that any migrational connections existed distribution further supports a derivation of the Zechstein between the Tethyan Ocean and the Zechstein Basin in Basin fauna without any input from the western Central the Late Permian. Tethys platforms immediately east of the Zechstein Basin. The southward migration from the northern Pangaean Acknowledgements Boreal faunas into the warmer settings of East Greenland seems to have taken place without major changes in We would like to thank Hans Arne Nakrem, Oslo, faunal composition judging from the very high degree of for introducing us to the bryozoan fauna in Svalbard and similarity between these faunas (Figs. 3–6). However, D.A.T. Harper, Copenhagen for helping with the statis- major changes did take place as migration progressed tical analyses. further southwards into the even warmer, in part evaporitic settings of the Zechstein Basin. Only members of References the orders Trepostomata and Fenestrata managed suc- cessfully to get established under the somewhat adverse Beauchamp, B., 1994. Permian climatic cooling in the Canadian conditions characterising this semi-isolated basin, and it Arctic. In: Klein, G.D. (Ed.), Pangea: Paleoclimate, Tectonics and can therefore be concluded that the main environmental Sedimentation During Accretion, Zenith and Breakup of a Super- continent. Geological Society of America Special Paper, vol. 288, threshold in the Atlantic rift-arm was located somewhere pp. 229–246. to the south of the East Greenland Basin. Beauchamp, B., Baud, A., 2003. Growth and demise of Permian biogenic chert along the northwest Pangea: evidence for end- 5. Summary and conclusions Permian collapse of thermohaline circulation. Palaeogeography, Palaeoclimatology, Palaeoecology 184, 37–63. Beauchamp, B., Desrochers, A., 1997. Permian warm- to very cold- During Early Permian times, the tropical Tethys Sea water carbonates and chert in the Sverdrup Basin–Barents Sea and the huge shelf along the northern margin of Pangea area, northwestern Pangea. In: James, N.P., Clarke, J.A.D. (Eds.), were connected through the seaway between Baltica and Cool-Water Carbonates. Society of Economic Paleontologists and Siberia allowing the migration of bryozoans as well as Mineralogists Special Publication, vol. 56, pp. 349–364. other benthos. During the mid-Permian, these marine Dallmann, W.K., Gjelberg, J.G, Harland, W.B., Johannessen, E.P., Keilen, H.B., Lønøy, A., Nilsson, I., Worsley, D., 1999. Upper connections were cut-off due to the beginning collision Palaeozoic lithostratigraphy. In: Dallmann, W.K. (Ed.), Lithos- between Baltica/Laurussia and Siberia, and distinctive tratigraphic Lexicon of Svalbard. Review and Recommendations bryozoan faunas began to develop. Rifting along the for Nomenclature Use. Upper Palaeozoic to Quaternary bedrock. North Atlantic rift system formed a marine seaway Norsk Polarinstitutt, Tromsø, pp. 25–126. between Norway and Greenland during the later parts Ernst, A., 2000. Permian bryozoans of the NW-Tethys. FACIES 43, 79–102. of the Permian which led to flooding of first the East Ernst, A., 2001a. 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