EUROPE/Timanides of Northern Russia 51 ophiolites and island-arc volcano-sedimentary assemblages, and the latter, towards the east, are covered by Mesozoic successions of the West Siberian Basin The timing of the Timanian Orogeny is constrained by the ages of the youngest sedimentary successions involved in the Precambrian deformation and the oldest unconformably overlying sediments The latter are generally Ordovician, but locally (beneath Kolguev Island and the Pechora Basin and on Novaya Zemlya) reach back into the Cambrian, the oldest strata (late Early Cambrian) occurring in central Novaya Zemlya The youngest strata involved in the Timanian deformation include tillites in southern areas and contains Vendian acritarchs Late Vendian successions in some Timanian foreland areas are developed in molasse facies Thus, it can be inferred that the Timanian Orogeny occurred in the Vendian (Late Vendian in the front of the orogen; perhaps earlier in the hinterland) and lasted at least until the end of the Vendian, during uplift and erosion of the orogen, prior to Early Cambrian peneplanation and then the start of Palaeozoic platform deposition along the Baltica margin The different parts of the Timanide Orogen are summarized below, starting in the foreland fold-andthrust belt and then continuing eastwards beneath the Pechora Basin to the metamorphic complexes of the Subarctic and Polar Urals and Novaya Zemlya Timanian Foreland Fold and Thrust Belt Two very different Neoproterozoic sedimentary successions are preserved along the western front of the Timanide Orogen, the one in the Southern and Middle Urals and the other further to the north-west In the Timan Range and north-westwards to the Varanger Peninsula, thick turbidite-dominated successions occur in thrust sheets emplaced southwestwards onto platform facies, shallow marine carbonate (often stromatolite-bearing) and siliciclastic formations These turbidites were apparently deposited along the margin of the East European Craton in continental slope and rise environments These sedimentary rocks occur in upright to SWvergent folds and are generally well preserved, with excellent characteristic sedimentary structures (graded bedding and Bouma sequences) and low grade of metamorphism (low greenschist facies) Only locally in the exposed thrust belt, on the Kanin Peninsula and northernmost Timan, are more deformed and metamorphosed sedimentary rocks present in the Timanide thrust sheets, providing evidence of the influence of regional high amphibolite facies metamorphism at depth within this part of the orogen Blueschists have also been reported in the northeasternmost parts of the Kanin Peninsula The turbidite-dominated successions are extensively intruded by pre-tectonic dolerite dykes and, in northern Timan, by an alkaline suite of gabbros, granites, and syenites, often nepheline-bearing, yielding zircon U/Pb ages of ca 615 Ma To the south-west of the main Timanide deformation front, Late Vendian generally non-marine siliciclastic successions in the Varanger Peninsula, the Mezen Basin, and further south-east in the orogen were derived from the Timanide hinterland to the north-east, and are inferred to be molasse In the southern Urals (see Europe: The Urals), the Neoproterozoic turbidite facies is not exposed, and thick (up to 15 km) intracratonic successions were deposited from the beginning of the Mesoproterozoic to the Late Neoproterozoic, dominated by shallowwater siliciclastic and carbonate formations with some rift volcanics and sub-volcanic intrusions These successions are called Riphean and are overlain by Early Vendian tillites and Late Vendian molasse, the latter a response to Timanian Orogeny further east The type area for Riphean stratigraphy is located in the core of a major Late Palaeozoic fold, the Bashkirian Anticlinorium, in the foreland fold-belt of the Urals (Figure 2) Beneath a major Ordovician unconformity, the folded and faulted Riphean and Vendian sedimentary rocks are overlain by a more deformed and, in part, more metamorphosed (amphibolite facies, locally with eclogites) allochthon, the Beloretsk Terrane Neoproterozoic turbidites, similar to those in the Timan Range, may have been deposited in the areas at present occupied by the hinterland of the Southern Urals; if this was the case, they are now in the unexposed footwall beneath the Beloretsk Terrane Further north, in the middle Urals (Figure 2), another major Uralian fold, the Kvarkush-Kamennogorsk Anticlinorium, like the Bashkirian Anticlinorium (above), also contains Proterozoic successions below a postTimanian, Ordovician unconformity The siliciclastic and carbonate formations of this region are thought to be Neoproterozoic in age, reaching up into Early Vendian tillites and, probably, Late Vendian molasse Of particular interest is the occurrence in the Kvarkush area of blue schists of Late Vendian (or possibly earliest Cambrian) age, thrust on to the other less metamorphosed, low greenschist facies sedimentary rocks Ordovician quartzites overlie these Precambrian rocks and structures with major unconformity Basement of the Pechora Basin From the Timan Range, the Timanide Orogen extends eastwards beneath the Palaeozoic and younger