RUSSIA 465 Central Taimyr was thrust southward to form the southern Taimyr thrust zone which consists of an imbricated Middle Carboniferous to Triassic sequence Its stratigraphy is generally similar to the Siberian Craton in the Tunguska Basin The position of Taimyr relative to other structures has been controversial It has been proposed that it might represent a continuation of Novaya Zemlya However in the 1980–1990s, the Arctic shelf was actively explored for oil New data were obtained, and it was suggested that the northern Taimyr is an exposed part of the Kara Plate, which occupies the adjacent Arctic shelf To the east, the Taimyr structures are truncated by Arctic oceanic floor Its western continuation is far from clear, but magnetic data suggest correlation of Pai-Khoi and Novaya Zemlya with Severnaya Zemlya and not with Taimyr (Figure 7) The Severnaya Zemlya islands consist of 6–7 km of Ordovician to Devonian deformed shallow-water sedimentary rocks with evaporites and felsic alkaline volcanics (456 Ma) They conformably overlie Cambrian rocks and their fossils are similar to those of the Novaya Zemlya archipelago Folded Ordovician to Devonian rocks are unconformably overlain by Carboniferous-Permian redbed sequences The timing of deformation is assumed to be Late Triassic, as in Taimyr, but no structural relationship has been recorded Novaya Zemlya and Pai-Khoi consist of Riphean to Lower Cambrian metamorphic rocks unconformably overlain by deformed Ordovician-Devonian terrigenous-carbonate rocks These are also unconformably overlain by Carboniferous-Triassic continental rocks deformed prior to Jurassic times Pai-Khoi, Novaya Zemlya, and Severnaya Zemlya reveal similar lithologies and similar unconformities The two regions are dextrally offset relative to each other along the Yenisei strike-slip fault that separates the Arctic shelf into the Kara and Svalbard plates and bounds the western margin of the Siberian Craton Tectonically, Severnaya Zemlya and Novaya Zemlya might represent an inverted rift structure West of Pai-Khoi and Novaya Zemlya are the Timanides, where Puchkov reported relic Late Vendian fold belts (600–540 Ma) The Timanides are poorly exposed, and an understanding of their structure is based on geophysical and drilling data There are two major terranes: in the south-west is the Izhma-Pechora passive margin with Riphean shales, felsic volcanics, and minor ultramafic intrusions; in the north-east is the Bolshaya Zemlya Terrane with Riphean intermediate volcanics and granitoids The passive margin of the terrane can be traced along the northern coast of the Kola Peninsula, whereas the island arc terrane is truncated by the East Barents Trough and Pai-Khoi structures The Timanides are overlain by Devonian to Jurassic rocks of the Pechora sedimentary basin The whole orogen and its sedimentary basin were thrust onto the East European Craton prior to Jurassic times Numerous listric compressional faults in the Pechora basin reflect the Urals collision In the middle of the Arctic shelf is the 1500 km long East Barents depression, extending parallel to the proposed Pai-Khoi–Novaya Zemlya–Severnaya Zemlya inverted rift Aplonov and his colleagues proposed that this depression might have a Palaeozoic oceanic crust over which lies up to 15–17 km of Middle Palaeozoic to Cretaceous sediments In the south, the East Barents depression continues as continental rifts in the base of the Pechora Basin In the north-east, it is truncated by the Arctic oceanic floor Altaid Collage The area between the East European and Siberian cratons and south of the Arctic shelf is occupied by the Altaid Orogenic Collage (Figure 2) The Russian portion of the Altaid Collage is concealed under the Mesozoic-Cenozoic sedimentary basin of western Siberia, being exposed in isolated orogens in the Urals, Altai-Sayan, and Transbaikalia Other exposures are in adjacent Central Asia (see Asia: Central; China and Mongolia), Mongolia, and China The Altaid Collage is separated into two domains along the giant Trans-Eurasian strike-slip fault, which strikes from Novaya Zemlya towards western Mongolia and then to the Mongol-Okhotsk suture, south of the Siberian Craton To the west is the Kazakhstan-Khingan Domain and to the north-east is the Altai-Mongol Domain Both domains have similar Terranes which were sinistrally offset during the Late Palaeozoic to Triassic by 1000 km The internal structure of the domains is oroclinal, and their axes are also sinistrally offset by 1000 km Altai-Mongol Domain The Altai-Mongol Domain consists of the ‘Caledonides’ and ‘Variscides’ (these terms are used here in different ways from their West European counterparts) The Caledonides, which occur in AltaiSayan and Transbaikalia, represent a portion of the Altaid Collage attached to the Siberian Craton and Neoproterozoic orogens (Figure 8) In the southwest, it is truncated by the Trans-Eurasian Fault The ‘Variscides’ occur in the Tom-Kolyvan Terrane in Siberia and the Khangai-Khentei Superterrane in Transbaikalia