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Structural Style and Evolution of the Pechora Basin, USSR

MALYSHEV, N. A., and V. V. UDIN Institute of Geology, Komi Science Center, Syktyvkar (Komi), USSR, and S. SCHAMEL,* Earth Sciences and Resources Institute, University of South Carolina, Columbia, SC

The Pechora basin is the complexly structured foreland depression west of the Northern Urals. The majority of the large, commonly hydrocarbon-bearing, anticlinal structures within the basin and the Uralian foothills are fault propagation folds. However, based on their relationship to the sub-Paleozoic basement and origin identified in high-resolution reflection seismic lines, two general classes of structures can be distinguished. The broad northwest-trending anticlinoria (Pechora-Kozhva, Kolva, and Sorokin swells) crossing the central and northern portions of the basin comprise en echelon anticlines formed above relatively steep basement-rooted faults. Folds of this group developed in the Permian, during the early phase of the Uralian orogeny, by left-lateral transpressional inversio of Late Devonian half-grabens that underlie the anticlinoria. The anticlinoria within the broad Timan Ridge, the southeast margin of the basin, may have a similar origin. A second group of fault propagation folds frames the basin on the east and northeast, comprising the frontal structures (Chernov, Chernyshov, and Vuktyl anticlines) of the Northern Urals and Pay-Khoy thrustbelts. These anticlines are formed at the leading edges of shallow detachments within middle Carboniferous and/or older strata. Curiously, they appear to be slightly younger than the anticlines in the foreland depression.

Spatial relationships between the anticlinoria and associated thrusts in the Pechora basin and those in the frontal zone of the Northern Urals point to strong mechanical control of individual thrust sheets in the Urals by the northwest-trending middle Paleozoic rifts within the basin. Furthermore, spatial and timing relations suggest that all of the structures in the Pechora basin and Northern Urals root on a common, deep crustal detachment and that much, if not all, of the basin is allochthonous.

 

AAPG Search and Discovery Article #91007© 1991 AAPG International Conference, London, England, September 29-October 2, 1991 (2009)