Intracontinental strike-slip faults as indicators for changing stress fields (Late Paleozoic of the Bohemian Massif, Germany)
Northwest-trending strike-slip zones of the Bohemian Massif were studied as to their Late Paleozoic shear sense. Upper Carboniferous dextral shearing was followed by minor sinistral slip during the Rotliegend (Lower Permian). Since these parallel-trending shear zones span a lateral distance of 250 kilometers, two different homogeneous(?) stress fields must have existed within the Bohemian Massif.
The eastern Bavarian ductile Danube/Pfahl shear zone displays a dextral simple shear fault pattern. Synthetic faults follow the geometry of HARDING's strain ellipse. Northern parts of the shear zone were reactivated left-laterally under transitional conditions from ductile to brittle as indicated by Rotliegend pull-apart basins, mylonite microfabrics and quartz-filled shear veins.
Farther north, Rotliegend sinistral slip occurred at the brittle "Frankische Linie" fault. It locally shows the shear pattern of a sinistral extensional strike-slip duplex which functioned as a pull-apart basin. The fault's southern termination is a sinistral leading extensional fan. Except in the fault's immediate vicinity, older dextral displacements of metamorphic rocks are the rule.
The Elbe zone at Dresden was intruded by the zoned, lazy Z-shaped Meissen pull-apart pluton during Upper Carboniferous dextral slip. Microfabrics of its outer syenodiorite zone indicate high and low temperature solid state dextral shearing. The mylonitized country rock's microfabrics indicate dextral shear sense. However, towards the southeast, microfabrics were observed suggesting younger opposite slip. Southwest of the Elbe zone, rhyolite-filled shear veins were formed by these sinistral movements.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California