The influence of salt layers on cover faulting during thick-skinned extensional faulting is examined using seismic examples from the salt basins offshore UK. The ratio of salt layer thickness to basement fault displacement is a key geometric parameter governing spatial offset between cover and basement fault segments. The influence of geological factors such as stratigraphic variation in salt thickness, basement fault zone geometry and basement fault growth through time on this parameter are individually examined. 3D models are constructed to illustrate the spectra of possible fault geometries which result from variations in these factors. Lateral stratigraphic variations within individual ‘salt’ layers are also considered, as are complications introduced by the addition of further salt layers into cover stratigraphy. Since diapiric intrusions occur after cover fault geometries are established and are localized by such faulting, an understanding of basement-cover fault relationships also illuminates salt diapir-basement fault relationships. An example from the Central North Sea diapir province is subject to such a genetic analysis, relating the diapir and its location to an underlying basement fault. The influence of salt on cover fault reactivation during basin inversion is discussed, focusin on the southern North Sea, where inhibition of reverse fault propagation from basement to cover is noted. It is suggested that analysis of local basement-cover relationships should form a first step in any attempt at a genetic classification of salt bodies.

The closure of the Uralian Ocean occurred in Early Permian-Early Triassic time. In the northern Ural fold belt, overthrusting to the west produced a major foreland basin to the west of the mountain chain. In contrast, in the northern extension of the Ural Orogen, the Taymyr fold belt, thrusting was directed to the SE. It is proposed that Novaya Zemlya, at the interface of these two zones, acted as a thin-skinned allochthonous nappe emplaced by gravity tectonics into a basin produced by rapid Permo-Triassic rifting in the eastern Barents Sea.

Internal deformation within the Eurasian continent during the Mesozoic and Cenozoic occurred in response to a series of discrete collisional events along its southern margin. Collisions are recorded from Late Triassic, Middle Jurassic, latest Jurassic, mid-Cretaceous and Late Palaeogene-Recent times. Periods of deformation recorded from sedimentary basins both close to and more distant from the southern margin of Eurasia can be related to these collisional events. The strain of each collision was accommodated both by intense deformation along the margin of Eurasia and by relative movement of continental blocks within the accretional collage of Eurasia along pre-existing heterogeneities. Additional mid-Jurassic and latest Cretaceous uplift events are not directly related to collisional events on the southern margin of the continent. Petroleum systems in both strike-slip dominated basins (such as the South Caspian and Turgay basins) and thrust-dominated basins (such as the Fergana and Afghan-Tajik basins) show the influence of deformation on trap formation and breaching as well as on the remigration and potential loss of hydrocarbons. Periods of deformation also have a direct influence on the timing of hydrocarbon generation.

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