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The extension of the lithosphere, controlling the development of rifted basins, is driven by a combination of plate-boundary forces, frictional forces exerted on the base of the lithosphere by the convecting asthenosphere and deviatoric tensional stresses developing over upwelling branches of the asthenospheric convection system. Although mantle plumes are not a primary driving force of rifting, they play an important secondary role by weakening the lithosphere and by controlling the level of rift-related volcanic activity. A distinction between “active” and “passive” rifting is only conditionally justified.The extension of the lithosphere, depending on its rate and magnitude, and the potential temperature of the asthenosphere, can cause by adiabatic decompression partial melting of the lower lithosphere and upper asthenosphere. In rift systems, the level and timing of volcanic activity is highly variable. The lack of volcanic activity implies “passive” rifting. An initial “passive” rifting stage can be followed by a more “active” one during which magmatism plays an increasingly important role. Magmatic destabilization of the Moho may account for the frequently observed discrepancy between upper and lower crustal extension factors. Combined with evidence for thermal thinning of the mantle–lithosphere, this suggest that the volume of the lithosphere is not necessarily preserved during rifting as advocated by conventional stretching models.The structural style of rifts is controlled by the rheological structure of the lithosphere, the availability of crustal discontinuities that can be tensionally reactivated, the mode (orthogonal or oblique) and amount of extension, and the lithological composition of pre- and syn-rift sediments. Simple-shear extension prevails in rifts that subparallel the structural grain of the basement. Pure-shear extension is typical for rifts cross-cutting the basement grain. Pre-existing crustal and mantle–lithospheric discontinuities contribute to the localization of rift systems.The duration of the rifting stage of extensional basins is highly variable. Stress field changes can cause abrupt termination of rifting. In major rift systems, progressive strain concentration on the zone of future crustal separation entails abandonment of lateral rifts. Depending on constraints on lateral block movements, crustal separation can be achieved after as little as 9 My and as much as 280 My of rifting activity.Syn-rift basin subsidence is controlled by isostatic adjustment of the crust to mechanical stretching of the lithosphere, its magmatic inflation and thermal attenuation of the mantle–lithosphere.Post-rift basin subsidence is governed by thermal reequilibration of the lithosphere–asthenosphere system. Deep-seated thermal anomalies related to syn-rift pull-up of the asthenosphere–lithosphere boundary have decayed after 60 My by about 65% and after 180 My by about 95%. The magnitude of post-rift subsidence is a function of the rift-induced thermal anomaly and crustal density changes, the potential temperature of the asthenosphere and initial water depths. Intraplate stresses can have an overprinting effect on post-rift subsidence. Stretching factors derived from post-rift subsidence analyses must be corrected for such effects. [Copyright &y& Elsevier]

Abstract: Four structural cross-sections through the central segment of the Upper Rhine Graben (URG) were balanced by means of Thermo-Tectono-Stratigraphic Forward Modelling (TTSF-Modelling). Results were compared to geometric retro-deformation of pre-rift reference horizons applying line length and area balancing methods. TTSF-Modelling with a deep necking level (>20km) and/or a high effective elastic thickness (Te≥15km) yielded extension values similar to those of geometric balancing, while modelling with shallower necking depths and/or lower Te yielded unrealistic high extension values. A best fit of geometric balancing, indicating 5km rift orthogonal extension, was reached by TTSF-Modelling with a Te of 15km and a ‘pre-rift’ necking depth of 29km coinciding with the Moho discontinuity. This is compatible with (a) the geophysically mapped Moho that does not shallow significantly beneath the central segment of the URG and its shoulders, (b) seismicity indicating brittle–elastic deformation of the entire crust and a-seismic, ductile deformation of the lithospheric mantle, (c) compensation of crustal faults and shear zones in the crust–mantle transition zone. Modelled time-extension paths imply rifting during the Middle Eocene to Early Miocene, a Late Miocene post-rift stage and renewed rifting during the Pliocene to recent. Apparent northward migration of extension in time is an effect of uplift processes, which are not related to rifting. Correcting for these, the extension history for the four cross-sections becomes very similar, suggesting plane strain deformation and rifting at very low strain rates of about 1.7×10−16 s−1 involving brittle–elastic deformation of the crust and ductile deformation of the highly viscous, high strength upper mantle that controls the position of the lithospheric necking level. [Copyright &y& Elsevier]

Abstract: The lithospheric memory is key for the interplay of lithospheric stresses and rheological structure of the extending lithosphere and for its later tectonic reactivation. Other important factors are the temporal and spatial migration of extension and the interplay of rifting and surface processes. The mode of extension and the duration of the rifting phase required to lead to continental break-up are to a large extent controlled by the interaction of the extending plate with slab dynamics. The finite strength of the lithosphere has an important effect on the formation of extensional basins. This applies both to the geometry of the basin shape as well as to the record of vertical motions during and after rifting. We demonstrate a strong connection between the bulk rheological properties of Europe's lithosphere and the evolution of some of Europe's main rifts and back-arc systems. The thermo-mechanical structure of the lithosphere has a major impact on continental break-up and associated basin migration processes, with direct relationships between rift duration and extension velocities, thermal evolution, and the role of mantle plumes. Compressional reactivation has important consequences for post-rift inversion, borderland uplift, and denudation, as illustrated by poly-phase deformation of extensional back-arc basins in the Black Sea and the Pannonian Basin region. [Copyright &y& Elsevier]