Basement influence on foreland thrust and fold belt development: an example from the southern Urals

The reactivation of two sets of pre-existing basement faults provided strong control on the geometric and kinematic evolution of the Paleozoic south Urals foreland thrust and fold belt. Pre-existing basement faults oriented subparallel to the Uralide structural grain were related to several stages of Precambrian deformation. Reactivation focused the deformation along these earlier faults, resulting in the subsequent incorporation of crystalline basement thrust sheets in the thrust belt at an early stage of its evolution. Pre-existing basement faults oriented subperpendicular to the developing thrust belt structural grain were related to aulacogens in the Archean crystalline basement that were filled by variable thickness of Riphean-aged sediments. These influenced the localisation and development of numerous structures in the thrust belt that caused along-strike structural changes related to lateral ramps. Recognition of these features and their influence on the geometric and kinematic evolution of the south Urals foreland thrust and fold belt are important for understanding seismic reflection fabrics in the south Urals thrust belt, and for potential field, 3-D geological, and kinematic modelling. (C) 1999 Elsevier Science B.V. All rights reserved.