Extensional basins of the former Soviet Union - - structure, basin formation mechanisms and subsidence history

We review the structure and evolution of a number of Riphean-Phanerozoic rifts and extensional basins within the territory of the former Soviet Union (FSU). Horst-and-graben formation in strong crustal and subcrustal lithosphere layers can explain the multi-trough character of rift systems observed in the Russian platform, the Vilyuy rift, the West Siberian rift system, the Pechora-Kolva rift system and the Laptev Sea rift. Many features in the evolution of these rifted basins are incompatible with predictions of classical stretching models. Basin subsidence often occurs in the absence of any noticeable stretching and over time scales much longer than predicted by models of thermal subsidence. Other observations include a time gap between rifting and the onset of post-rift basin subsidence of tens to hundreds Ma and a correlation in timing of subsidence phases of rifted basins and platforms with opening and closure events of adjacent ocean basins. These observations point to an important role for mechanisms such as eclogite formation within or beneath the lithosphere as well as intraplate compression and stress-induced lithospheric deflection.