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[1] The Urals Seismic Experiment and Integrated Studies (URSEIS), Mikhailovsky, and Europrobe's Seismic Reflection Profiling in the Urals (ESRU) reflection seismic profiles provide constraints for the construction of balanced and restored geological cross sections across the southern and middle Urals foreland. The profiles image the transition from the undeformed foreland basin to the frontal structure of the foreland thrust and fold belt, the location of the basal detachment and the location of the ramp down into the middle or lower crust. In the URSEIS and ESRU profiles, the transition into the undeformed foreland basin is imaged as an emergent west-vergent thrust that deforms a westward thickening package of reflections related to synorogenic sediments, whereas in the Mikhailovsky profile, it is a buried system of imbricate thrusts, in all three data sets, the western flank of the foreland thrust and fold belt is imaged in the seismic data as an imbricate thrust system developed above a basal detachment located in either the upper part of the Neoproterozoic basement sediments or the lower part of the Paleozoic continental margin sediments. Truncation of reflections related to the undeformed sediments in the footwall to the imbricate thrust system mark the location of the ramp down of the basal detachment into the middle or lower crust beneath the basement-cored anticlines along the eastern flank of the thrust belt. The URSEIS and ESRU profiles image the basement-cored anticlines as predominantly east dipping reflections that extend into the middle and lower crust. Rocks in these anticlines record at least one phase of pre-Uralide deformation and, at least in part, the reflectivity is due to this deformation event. Balanced and restored cross sections constructed along the three profiles indicate that the minimum shortening is about 20-25 km. Citation: Brown, D., C. Juhlin, A. Tryggvason, M. Friberg, A. Rybalka, V. Puchkov, and G. Petrov (2006), Structural architecture of the southern and middle Urals foreland from reflection seismic profiles, Tectonics, 25, TC1002, doi:10.1029/2005TC001834.

A new compilation of deep seismic reflection data, in combination with the results of recent geological and isotopic investigations, provides the basis for significantly refined structural and evolutionary models of the Middle Urals. Many of the major structural boundaries observed at the surface (e.g. Main Uralian Thrust, Main Uralian Normal Fault, Serov-Mauk Fault, Prianitchnikova Shear Zone) can be followed on the seismic reflection data to depths of 8-15 km. Only a few features can be traced through the horizontal to shallow dipping zones of middle-crustal reflectivity that extend beneath much of the Middle Urals. Exceptions might be the Deevo Thrust and a newly discovered deep band of moderately dipping reflections beneath the West Siberian Basin that may represent the remnants of an ancient subduction zone. The reflectivity of the lower crust and Moho are similar beneath the hinterland of the Urals and below the western part of the West Siberian Basin, suggesting that in both places they have the same extensional origin. Accretion of various exotic terranes to the eastern margin of Baltica during Late Palaeozoic time involved considerable shortening of the continental margin. The accreted terranes (e.g. Tagil, Petrokamensk and Alapaevsk Arc Complexes) consist mostly of island-arc material formed during Mid- and Late Palaeozoic time. Closely associated with the island arcs are several high-grade metamorphic complexes (e.g. Salda and Murzinka--Adui Complexes) that were exhumed during and after Late Palaeozoic convergence. Towards the end of the orogeny, several north-south-trending strike-slip faults (e.g. Sisert Fault) were active. After the orogeny, major periods of tectonism and magmatism in the Middle Urals resulted in the extrusion of the Siberian trap basalts, crustal stretching and/or underplating, and the formation of the West Siberian Basin, the planet's largest intracontinental sedimentary basin. Finally, a period of renewed thrust faulting, often reactivating older faults, led to the inversion of the Mesozoic basins. Keywords: Uralide Orogen, West Siberian Basin, Palaeozoic, Mesozoic, seismic profiling.

Three overlapping seismic reflection data sets were obtained in the Middle Urals as part of the Europrobe's seismic reflection profiling in the Urals initiative. This data has been used to address issues including the interpretation of the current crustal structure in the Middle Urals and its geodynamic evolution. It has been established that the bivergent crustal structures are the Main Uralian and associated faults in the west and the Trans-Uralian Thrust Zone and other west dipping crustal shear zones in the east. The major shear zones seem to be listric into and/or truncated by zones of middle to lower crustal reflectivity.