We have analysed 129 stratigraphic sections from the Timan-Pechora basin, from its adjacent continental shelf and from the South Barents Sea basin, in order to determine whether existing models of extensional sedimentary basin formation can be applied to these intracratonic basins or whether new mechanisms of formation need to be invoked. The subsidence history of each section has been calculated using standard backstripping techniques. An inverse model, based on finite-duration lithospheric stretching, has then been used to calculate the distribution of strain rate as a function of time required to fit each subsidence profile. Results demonstrate an excellent fit between theory and observation. By combining our analysis with independent field-based and geophysical observations, we show that the Timan-Pechora basin underwent at least four phases of mild lithospheric stretching during the Phanerozoic (β < 1.2). These phases occurred in Ordovician, Late Ordovician-Silurian, Middle-Late Devonian and Permian-Early Triassic times. Growth on normal faults, episodes of volcanic activity and regional considerations provide corroborative support for the existence of all four phases. Although less well constrained, subsidence data from the South Barents Sea basin are consistent with a similar Early-Middle Palaeozoic history. The main difference is that Permian-Early Triassic extension is substantially greater than that seen onshore. This similarity implies structural connectivity throughout their respective evolutions. Finally, subsidence modelling demonstrates that rapid foreland basin formation, associated with the Uralian Orogeny, was initiated in Permo-Triassic times and is confined to the eastern margin of the Timan-Pechora basin. Coeval foreland subsidence does not occur on the eastern margin of the South Barents Sea basin, supporting the allochthonous nature of Novaya Zemlya. The most puzzling result is the existence of simultaneous lithospheric extension and foreland loading in Permian-Early Triassic times. This juxtaposition is most clearly seen within the Timan-Pechora basin itself and suggests that convective drawdown may play a role in foreland basin formation.
The setting of the petroleum basins of Russia varies from Precambrian cratons to Tertiary active margins. Four economically and strategically important basins illustrate this diversity. The North Sakhalin Basin is a Tertiary strike-slip basin supplied with Oligocene-Pliocene reservoir sands, and seal- and source-forming mudrocks by the palaeo-Amur delta. Miocene diatomites are additional source rocks. Plio-Pleistocene structuring was crucial to hydrocarbon entrapment. The West Siberia Basin contains identified oil reserves of 60 billion bbl and 1400 tcf gas, respectively 47% of the oil reserves of the CIS and 77% of its gas reserves. The world-class Upper Jurassic Bazhenov source rock and a high impedance entrapment style are the keys to the productivity of the basin. The Timan-Pechora Basin contains Ordovician-Triassic reservoirs and a major Late Devonian source rock. Hydrocarbon preservation is good despite the basin's complex history of subsidence and inversion. On the Siberian Platform in East Siberia 12 billion BOE reserves are sourced, reservoired and sealed by Upper Precambrian-Cambrian rocks. Protracted preservation times there reflect a stable geological setting.
The Morris Bugt Group, originally proposed in western North Greenland, is now extended across the whole of North Greenland. One new formation, the Kap Jackson Formation, is described; it includes two members, the Gonioceras Bay and Troedsson Cliff Members, which correspond to earlier formations of the same names. In the Washington Land - western Peary Land region the group comprises the Kap Jackson, Cape Calhoun and Aleqatsiaq Fjord Formations. The Børglum River and Turesø Formations of the Peary Land - Kronprins Christian Land region are here added to the group. New data on the age of the formations based on conodont biostratigraphy are given, and correlations with Arctic Canada, East Greenland and Svalbard are discussed.
Conodont colour alteration data for the Lower Palaeozoic strata of the North Greenland carbonate platform indicate a pattern of increased thermal maturity northwards within the Franklinian Basin. There is little variation in values through the Canadian–Llandovery (Lower Ordovician–Lower Silurian) interval at any given locality. A simplified thermal model for the platform suggests that the predominant control of conodont colour alteration and thermal maturation was maximum depth of burial, which occurred during the mid- to late Silurian. A preliminary integrated scheme for conodont and organic thermal maturity indicators can be compiled from the data now available from North Greenland.
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