Print this pageExtensional Basins in the Northern West Siberia and Kara Sea
Valeriy I. Savchenko1, Erik Henriksen2, Tamara A. Kirjukhina1, Maria Ogarkova1, Ivan Panarin1, and Ivan Kurasov1
1Geological, Moscow State University, Moscow, Russia.
2StatoilHydro, Harstad, Norway.
The West Siberia deep extensional basin has an intracratonic setting, where sediments are 15 km thick or more. The Earth crust base (“Moho” boundary) varies from 40-42 to 33-35 km. Conrad boundary is fixed at 20-25 km depth. The West Siberia intracratonic rift system is defining the main extensional basin submergence. According to the seismic data there is the system of the linear elongated inverted swells on the top of the Palaeozoic, separated by grabens and troughs filled with Triassic sediments. V.S.Surkov defines this zone as the West Sibera Triassic rift system. (Surkov et al,1981, 2002). This zone is likely to be of more ancient origin and it has inherited the Palaeozoic extensional basin, the system of grabens was formed already in Rifean, which in the Early or Middle Palaeozoic could regenerate. The inverted structures had been formed by the end of Palaeozoic and defined the structural configuration of the acoustic basement of the region. These Palaeozoic linear inverted structures are identified by negative gravity and magnetic anomalies. Triassic grabens were formed between them and Triassic sediments overlap and pinch out onto the uplifted structures. Within the Kara shelf the West Siberia intracratonic rift system is limited by the Payhoy monocline in the south-west and the East Kara Steps in the north-west. Both these positive tectonic elements could be the shoulders of the ancient Palaeozoic West Siberia rift system, in its Kara part.
The extensional regional rift system is traced for thousands kilometers and it is confirmed by the gravity and magnetic anomalies. The West Siberian intracratonic rift system includes the inverted swells and grabens separating them. In some individual places the inversion causes linear folding. Large inverted swells within the West Siberia intracratonic rift system - the Yamburg, Urengoy, Nurminsky and others. They extend into the Kara Sea where the Rusanovsky and Leningradsky swells correspond to them. The maximum depths of the basement within the West Siberia rift system amount to 12-14 and more kilometers.
AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia