Structure of the West Carpathian accretionary wedge: insights from cross section construction and sandbox validation

The restoration of structures along balanced cross sections through the Wes t Carpathian accretionary wedge and pseudo-3D restoration in the Smilno Tec tonic Window area shows that various defined units contain sediments from M agura and Silesian depositional areas. The shortened Magura succession was detached at the Upper Cretaceous stratigraphic level. The shortened Silesia n sedimentary package was detached at the Lower Cretaceous stratigraphic le vel. The Magura succession was the southwestern neighbor of the Silesian su ccession in a large depositional system. Both sedimentary packages were sho rtened during the Paleogene and the Magura succession was later thrust over the Silesian succession as an out-of-sequence oblique thrust during the Ne ogene. The general shortening mode is piggy-back. Thrust geometries are cre ated by both fault-bend and fault-propagation folding. The common out-of-se quence thrusting is caused by the involvement of the basement in the shorte ning and by interplay of friction and erosion. The influence of basal frict ion on thrust sheet length is validated by sand-box models. Variations in f riction along the basal thrust include low friction, documented by subhoriz ontal veins with vertically grown fibers and long thrust sheets, medium fri ction, indicated by duplexing and high friction, indicated by antiformal st acks and back thrusting. (C) 1999 Elsevier Science Ltd. All rights reserved .