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 stron g control on the geometric and kinematic evolution of the Paleozoic south U rals foreland thrust and fold belt. Pre-existing basement faults oriented s ubparallel to the Uralide structural grain were related to several stages o f Precambrian deformation. Reactivation focused the deformation along these earlier faults, resulting in the subsequent incorporation of crystalline b asement 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 crys talline basement that were filled by variable thickness of Riphean-aged sed iments. These influenced the localisation and development of numerous struc tures in the thrust belt that caused along-strike structural changes relate d to lateral ramps. Recognition of these features and their influence on th e 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 kine matic modelling. (C) 1999 Elsevier Science B.V. All rights reserved.