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

Abstract

The restoration of structures along balanced cross sections through the West Carpathian accretionary wedge and pseudo-3D restoration in the Smilno Tectonic Window area shows that various defined units contain sediments from Magura and Silesian depositional areas. The shortened Magura succession was detached at the Upper Cretaceous stratigraphic level. The shortened Silesian sedimentary package was detached at the Lower Cretaceous stratigraphic level. The Magura succession was the southwestern neighbor of the Silesian succession in a large depositional system. Both sedimentary packages were shortened during the Paleogene and the Magura succession was later thrust over the Silesian succession as an out-of sequence oblique thrust during the Neogene. The general shortening mode is piggy-back. Thrust geometries are created by both fault-bend and fault-propagation folding. The common out-of-sequence thrusting is caused by the involvement of the basement in the shortening and by interplay of friction and erosion. The influence of basal friction on thrust sheet length is validated by sand-box models. Variations in friction along the basal thrust include low friction, documented by subhorizontal veins with vertically grown fibers and long thrust sheets, medium friction, indicated by duplexing and high friction, indicated by antiformal stacks and back thrusting.