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Mark Allen, University of Durham (United Kingdom)
Lester Anderson, ARKeX (United Kingdom)
Misha Buslov, Siberian Branch, Russian Academy of Sciences (Russian Federation)
Clare Davies, Woodside Energy (Australia)
Inna Safonova, Siberian Branch, Russian Academy of Sciences (Russian Federation)
Roger Searle, University of Durham (United Kingdom)
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The West Siberian Basin is an important example of intracontinental rifting because of its high width (>1000 km) and vast area (>2 million km2). Academic interest is strengthened by the association of rifting with the Siberian flood basalt magmatism at the Permo-Triassic boundary, and the possibility that these eruptions are linked to the end-Permian mass extinction. Hydrocarbon reserves in post-rift sediments add another impetus for understanding the basin's evolution.
Basement to the West Siberian Basin is a collage of microcontinental blocks and accretionary complexes, generated during much of the Palaeozoic in the Altaid orogeny. Rift geometries suggest a component of right-lateral, north-south shear during east-west extension (present co-ordinates). Several major exposed faults at the basin margins, mainly within the Altaid orogenic belt, underwent right-lateral strike-slip in the Late Permian - Early Triassic interval. The combined datasets show that the Siberian flood basalts were erupted during right-lateral oblique extension between the Urals and the Siberian craton, centred on a triple junction in the northeast of the West Siberian Basin. This triple junction is a plausible site for plume impact, associated with the flood basalt generation and eruption. Details of the rift structure are buried by the blanket of Mesozoic strata, deposited during post-rift thermal subsidence. The Mesozoic stratigraphic record of the satellite Kuznetsk Basin, to the south of the West Siberian Basin, shows angular unconformities, for example near the Triassic-Jurassic boundary.
These are related to pulses of deformation and uplift in the Altaids further south, but the impact on the interior of the West Siberian Basin is unclear. Geomorphology shows subtle, active, long wavelength deformation in the West Siberian Basin, presumably related to a far-field effect of the India-Asia collision. There is only localised evidence for conventional inversion structures, but the pattern of folding reveals a strong correlation with the location of rift, or even pre-rift basement faults.
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