464 RUSSIA in the 1990s revealed a Carboniferous age In addition, isotopic dating of some regionally metamorphosed rocks in the Patom Highlands also revealed a Carboniferous age This raised speculations that the Baikalides might be a Caledonian Orogen Geologically, the Patom Highlands consists of two major parts In the north is a Baikal-Patom passive margin of Middle to Upper Riphean carbonateterrigenous rocks deformed into linear folds These rocks are unconformably overlain by VendianCambrian molasse Together they were thrust onto the Siberian Craton in the Middle Devonian To the south is the Barguzin-Vitim Terrane which is separated from the passive margin by a suture with Riphean ophiolites The Barguzin-Vitim Terrane is exposed in small fragments, consisting of metamorphosed Riphean accretionary wedge and island arc rocks Yenisei Ridge The Yenisei Orogen in the west of the Siberian Craton (Figure 1) is considered as an equivalent and continuation of the Baikalides Deformed passive margin rocks occupy the bulk of the ridge It has been demonstrated that in the west there is a suture with Late Riphean ophiolites and an island arc terrane The folded structure is intruded by Neoproterozoic granites Passive margin rocks were thrust onto the Siberian Craton, possibly in mid-Palaeozoic times Northern Taimyr, Arctic Shelf and Timanides The east–west trending Taimyr Orogen is an imbricated structure produced during Mesozoic thrusting to the south (Figure 7) It has been suggested that this orogen was a result of collision between the Kara Plate to the north and the Siberian Craton to the south Northernmost Taimyr is a deformed Neoproterozoic to Early Palaeozoic passive margin of the Kara Plate, consisting of flysch and carbonate sequences which were regionally metamorphosed They were earlier considered as Precambrian rocks: however, recent study has showed that metamorphism is Late Palaeozoic in age and might have taken place during the emplacement of 300–264 Ma collisional and post-collisional granitoids The Main Taimyr Thrust separates northern and central Taimyr The latter hosts two terranes (Mamont-Shrenk and Faddey) with Neoproterozoic island arc rocks and ophiolites (740–820 Ma) which were obducted 650 Ma ago onto Neoproterozoic carbonates, which are also thrust on top of Vendian to Early Carboniferous terrigenous-carbonate rocks of central Taimyr, part of the Siberian Craton Another ophiolite belt inside northern Taimyr might be a root zone where the actual suture might be located If so, northern Taimyr should be separated into two terranes, the northern one representing the Kara Plate and the southern one a deformed passive margin of the Siberian Craton Figure Tectonics of the Arctic shelf and adjacent regions (compiled by Yakubchuk, using data by Bogatskiy et al and Bogdanov et al.) The Yenisei Fault separates the Arctic shelf into the Kara and Svalbard plates Severnaya Zemlya is probably a continuation of Novaya Zemlya The Barents extensional trough bounds the Svalbard Plate in the south A major strike slip fault might separate the west east trending structures of the Arctic shelf and Siberian Craton