Ar-40/Ar-39 dates from the West Siberian Basin: Siberian flood basalt province doubled

Widespread basaltic volcanism occurred in the region of the West Siberian Basin in central Russia during Permo-Triassic times. New Ar-40/Ar-39 age determinations on plagioclase grains from deep boreholes in the basin reveal that the basalts were erupted 249.4 +/- 0.5 million years ago. This is synchronous with the bulk of the Siberian Traps, erupted further east on the Siberian Platform. The age and geochemical data confirm that the West Siberian Basin basalts are part of the Siberian Traps and at least double the confirmed area of the volcanic province as a whole. The larger area of volcanism strengthens the link between the volcanism and the end-Permian mass extinction

The timing and extent of the eruption of the Siberian Traps large igneous province: Implications for the end-Permian environmental crisis.

We present new high-precision 40Ar/39Ar ages on feldspar and biotite separates to establish the age, duration and extent of the larger Siberian Traps volcanic province. Samples include basalts and gabbros from Noril'sk, the Lower Tunguska area on the Siberian craton, the Taimyr Peninsula, the Kuznetsk Basin, Vorkuta in the Polar Urals, and from Chelyabinsk in the southern Urals. Most of the ages, except for those from Chelyabinsk, are indistinguishable from those found at Noril'sk. Cessation of activity at Noril'sk is constrained by a 40Ar/39Ar age of 250.3 ± 1.1 Ma for the uppermost Kumginsky Suite.\ud \ud The new 40Ar/39Ar data confirm that the bulk of Siberian volcanism occurred at 250 Ma during a period of less than 2 Ma, extending over an area of up to 5 million km2. The resolution of the data allows us to confidently conclude that the main stage of volcanism either immediately predates, or is synchronous with, the end-Permian mass extinction, further strengthening an association between volcanism and the end-Permian crisis. A sanidine age of 249.25 ± 0.14 Ma from Bed 28 tuff at the global section and stratotype at Meishan, China, allows us to bracket the P–Tr boundary to 0.58 ± 0.21 myr, and enables a direct comparison between the 40Ar/39Ar age of the Traps and the Permo–Triassic boundary section.\ud \ud Younger ages (243 Ma) obtained for basalts from Chelyabinsk indicate that volcanism in at least the southern part of the province continued into the Triassic