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Teper, L (2000). Geometry of fold arrays in the Silesian-Cracovian Region of southern Poland, In: J.W. Cosgrove and M.S. Ameen (eds.) Forced Folds and Fractures. Geol. Soc. London. Spec. Publs. 169, 167-179.

Geometry of fold arrays in the Silesian - Cracovian Region of southern Poland

Abstract

A zone of deformation characterised by en échelon folds extends along the NE margin of the Upper Silesian Coal Basin in southern Poland. The zone is well exposed by mining in numerous collieries where the deformation involving Upper Carboniferous strata can be observed. Folds and associated faults form a structural pattern consistent with an origin in dextral convergent wrenching on both the principal deep-seated fracture and subsidiary faults affecting crystalline basement beneath this part of the basin. The zone is crosscut by sublatitudinal belts of folds which, according to their geometrical parameters, seem to result from alternate transcurrent shearing along W-E oriented fractures of the basement, sinistral in one case and dextral in the other. Among folds caused by concentrated operation of force couple whose vectors lie in horizontal plane, there are examples of bending folds occurring in each array resulting from vertical component of movement of deep-seated fault blocks. Dimension of the folds changes with depth. Axial trend and inclination of axial surfaces differ with distance from the basement fault trace. Length of fold segments strongly depends on axes orientation. Widely distributed evidences of interlayer slip demonstrate a variable spatial distribution of tectonic-transport direction in the sedimentary sequence. Above-mentioned features and other geometrical attributes of the fold arrays enable to determine dynamics of forcing structures during Variscan tectogenesis and display hierarchical structure of the basement boundary zones. Examples from the Silesian-Cracovian Region suggest that drape folds can sometimes be originated in conditions provided by strike-slip regime.

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