The Timanide, Caledonide and Uralide orogens in the Eurasian high Arctic, and relationships to the palaeo-continents Laurentia, Baltica and Siberia D. G. GEE, O. K. BOGOLEPOVA & H. LORENZ Department of Earth Sciences, Uppsala University, Villava ¨gen 16, SE-752 36, Uppsala, Sweden (e-mail: david.gee@geo.uu.se) Abstract: Recent studies of structure, stratigraphy and isotope geochronology on Svalbard and East Greenland have provided a foun- dation for reconstructing the Laurentian margin of the Arctic segment of the North Atlantic Caledonides. The axial zone of the high Arctic, Barentsian Caledonides has been inferred to trend northwards through the Barents Shelf to the northern edge of the Eurasian margin between Kvitøya (easternmost Svalbard) and western Franz Josef Land, based on analysis of drill-cores that sampled the pre- Carboniferous basement beneath Alexandra Island. The deformation front of the Barentsian Caledonides has been inferred to trend northeastwards between Franz Josef Land and Novaya Zemlya. The North Kara Terrane, reaching from Severnaya Zemlya (SZ) and northernmost Taimyr in the east to northern Novaya Zemlya in the west, comprises the northernmost foreland to the Barentsian orogen. Four lines of independent evidence are presented here demonstrating that the North Kara Terrane is a direct northerly continu- ation of the Timanide domain, the latter composing the Neoproterozoic accreted margin of Baltica in the Timan – Pechora – Urals region. These lines of evidence, all from October Revolution Island (SZ), include: (1) a westerly source for Old Red Sandstones successions, with ‘Caledonian’ fish fauna and detrital muscovites yielding Ar/Ar ages of c. 450 Ma; (2) Ordovician igneous rocks containing c. 550 Ma xenocrysts; (3) Cambrian turbidites with c. 545 Ma detrital muscovites; (4) Cambro-Silurian fauna with many species shared with Baltica. In addition, the Neoproterozoic turbidites of northern Taimyr have been previously reported to contain c. 560 Ma zircon populations, a signature that has been recently found in similar lithologies from Bol’shevik Island (SZ). All these late Vendian ages are characteristic of the Timanide Orogen of the Timan–Pechora–Novaya Zemlya region and, together, indicate that the North Kara Terrane was not an independent ‘plate’ or ‘microcontinent’ in the Palaeozoic, as previously proposed, but an essen- tial part of southernmost (Ordovician coordinates) Baltica. Comparability of the evolution of the Timanian margin of the North Kara Terrane with the contemporaneous Baikalian evolution of adjacent Taimyr, together with the lack of evidence of Palaeozoic oceanic rocks and Uralian collisional, high-pressure metamorphic assemblages in Taimyr, suggests that the palaeo-continents Siberia and Baltica were never separated by a major ocean in the high Arctic. The Palaeozoic geology of the Eurasian high Arctic, from Sval- bard in the west to Severnaya Zemlya in the east (Fig. 1), has long been a matter of dispute and speculation. Most of the area is covered by sea, ice and a Cenozoic–Mesozoic blanket of sedi- ments. The track of the Caledonide orogen northwards, from the Scandes of northernmost Norway, across the Barents Shelf to Svalbard, its discordant relationship to the NW-trending Timanide orogen of northwestern Russia, the extension of the latter to the north into Novaya Zemlya, and its truncation in the east by the Uralian orogenic front have been widely treated in the literature; the relationship of all these old orogens to the Palaeozoic to early Mesozoic deformation of Taimyr and Severnaya Zemlya has remained enigmatic. For many decades, parts of Svalbard have been known to have Laurentian affinities (Harland 1997, and references therein; Gee & Teben’kov 2004). The Timanides (Gee & Pease 2004) have been accepted as an essential late Neoproterozoic component of the eastern (today’s coordinates) margin of Baltica, flanking the Archaean and Palaeoproterozoic core (the East European Craton) of this Early Palaeozoic continent. The southern and central domains of Taimyr have been shown to have unambiguous Siberian affinities (Sobolevskaya et al. 1995; Tesakov et al. 1995). Also, between Baltica and Siberia, a relatively small continental region, centred on Severnaya Zemlya and including northern Taimyr, referred to as the Kara ‘block’ or ‘plate’ or ‘microconti- nent’ (called here the North Kara Terrane), has been thought by most workers to be an independent unit, perhaps part of a larger continental assemblage, Arctida, that once may have dominated the northern polar regions (Zonenshain & Natapov 1987; Zonenshain et al. 1991). Related to these questions about the possible prolongation of these Palaeozoic orogens into the Eurasian high Arctic shelf and their interrelationships, has been the speculation concerning their continuity even further northwards and westwards prior to the opening of the Arctic Basin (Fig. 1). The compelling evidence of sea-floor spreading in the Eurasia Basin, with separation of a microcontinent, Lomonosova, from the Eurasian margin in the Early Cenozoic (Kristoffersen 2000; Jokat et al. 2003) to form the Lomonosov Ridge, implies that the latter is probably underlain by Mesozoic, Palaeozoic and Precambrian complexes comparable with those of northernmost Eurasia. This conclusion can thus be used to test hypotheses for the opening of the Amerasia Basin, a subject that will be left for another occasion. We focus here on Baltica – North Kara – Siberia relationships. The Barentsian Caledonides Recent work on Svalbard, summarized by Gee & Teben’kov (2004), and on eastern Greenland by Higgins & Leslie (2000) and Higgins et al. (2004), has shown that most of Svalbard’s Cale- donian terranes are direct northerly continuations of the Caledo- nides of eastern Greenland (Fig. 2). In particular, structural and stratigraphical similarities of the two eastern complexes on Sval- bard, the West Ny Friesland Terrane (Witt-Nilsson et al. 1998) and the Nordaustlandet Terrane (Gee et al. 1995), with the NE Greenland and Central East Greenland thrust complexes, respect- ively, extend in time from the late Palaeoproterozoic to the Early Palaeozoic. They leave little doubt that eastern Svalbard’s Proter- ozoic and Cambro-Ordovician bedrock composed an essential part of the western flank of the North Atlantic – Arctic Caledonides during the Caledonian orogeny (Gee 2005a). The latest studies of Nordaustlandet (Teben’kov et al. 2002; Johansson et al. 2004, 2005) have shown that metamorphic grade and intensity of deformation increase towards the east. High-grade complexes, with widespread migmatization, assumed by the early Svalbard explorers, from Nordenskjold (1866) and Sandford (1956) to Krasil’shikov (1973) and Harland (1997), to be ancient cratonic basement, have proved to be Caledonian high-T – low-P terranes with widespread zircon crystallization at From:GEE, D. G. & STEPHENSON, R. A. (eds) 2006. European Lithosphere Dynamics. Geological Society, London, Memoirs, 32, 507–520. 0435-4052/06/$15.00 # The Geological Society of London 2006. 507