Cretaceous collision and indentation in the West Carpathians: View based on structural analysis and numerical modeling

Abstract

A model of indentation of a rigid promontory into weak metasedimentary rocks during Cretaceous convergence is suggested for tectonic evolution of southern part of West Carpathians. An early arcuate cleavage fan has developed in front of northward moving southern rigid basement block. The interaction of the moving indenter with western stationary basement promontory is responsible for development of the boundary-parallel shear zone along which the main southern indenter is shifted to the east. This results in development of a new steep transpressional cleavage overprinting the early fabric. Eastward displacement of the southern indenter causes the development of a thrust zone parallel to the margin of the eastern stationary promontory. A proposed numerical model of the deformation of a thin viscous sheet in front of oval rigid indenter reliably simulates the development of the observed deformation pattern. Modeled discrete partitioning between the western promontory and the indenting block fully agrees with the observed secondary cleavage associated with the transpressional shear zone. Our numerical model interconnects this complex kinematic frame with finite strain pattern, which was to date possible only for simple boundary conditions. In addition, the model explains the polyphase cleavage patterns in terms of complex shapes of promontories and changes in movements of indenting blocks. Copyright 2003 by the American Geophysical Union.