West Siberian Basin
The West Siberian basin lies between the Ural mountains and the Siberian craton to its east. It corresponds to the geographic region of the West Siberian plain. Deposition in rift valleys resulting from prolonged subsidence of the Triassic Koltogor-Urengoy graben in an intra-cratonic sag basin beginning in the Jurassic has resulted in a thick 'basin fill' of sedimentary deposits ranging from Jurassic to Cenozoic in age. There are two major north-south trending rift structures of Triassic age buried beneath the basin fill: the Urengoy and the Khudosey rift. These rifts are mainly filled with Lower Triassic basic volcanic rocks.
The West Siberian basin and its offshore portions in the south Kara sea are the largest oil province in the world. It has an area of 2,200,000 square kilometres (850,000 sq mi) and the USGS estimates oil and gas reserves of 360 billion barrels of oil equivalent in the basin.
Read more about this topic: Geology Of Russia
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