Quantitative structural analyses and numerical modelling of ...

J. KonopaÂsek et al. / Journal of Structural Geology 23 2001) 1373±1392 1389aNS 2L 2L 2bD 3 kink-bandsNL 1L 2L 3D 4 kink-bandsFig. 11. Schematic sketches showing the evolution of large-scale structures in time. a) Situation after the late D2 deformation is interpreted as a result ofbuttressing of the allochthonous unit from the west. Continuous E±W compression leads to the development of large-scale periclinal structures the MeÏdeÏnecsynform and Oberwiesenthal structure). b) Subsequent N±S compression leads to refolding of the late D2 structures by km-scale antiforms the MeÏdeÏnec andKlõÂnovec antiforms). Brittle-ductile structures in the ¯at lying S 2 foliation appear during the late D3 deformation. Disappearance of the N±S oriented D3compressive stress leads to strengthening of the role of overburden. Vertical D4 compression produces D4 kink-band folds to kink-bands.show 5% increments of strain imposed on a former D2fabric ellipsoid.In those areas that were not affected by the D3 deformation,we have identi®ed three types of the D2 strains symmetriesFig. 8) and these approximately represent startingpoints of trajectories in the Fig. 10. An attempt was made to®nd those ®nite strains observed in natural samples from themegafold limbs. Moreover, different ®nite D3 fabrics mustbe produced after an equal number of increments of the D3deformation. Our analysis demonstrates Fig. 10) that thiscase is reached when most of the imposed shortening isaccommodated by elongation of former Y-axis and smallchange of former X-axis. For plane-strain to constrictionalvertical D2 fabric with higher strain intensity Fig. 10a),65