Stożek aluwialny pre-Kaczawy - przykład sedymentacji w czynnej strefie przesuwczej, plio-plejstocen, Sudety
Abstract
THE PRE-KACZAWA ALLUVIAL FAN – AN EXAMPLE OF SEDIMENTATION IN AN ACTIVE WRENCH ZONE, PLIO-PLEISTOCENE AGE, SUDETIC MOUNTAINS
Summary
Synsedimentary tectonic activity along the Sudetic Marginal Fault, SW Poland, resulted in the evolution of an alluvial fan sedimentary system and development of deformational structures in a sequence of Plio-Pleistocene sediments. The early phase of sedimentation, related to the dip-slip effect of the Sudetic Marginal Fault, resulted in progradation of alluvial fan at the outlet of the Pre-Kaczawa River onto the downthrown Fore-Sudetic Block. The following strike-slip movements along the fault induced the shingled arrangement of successive fan lobes and development of deformational structures in alluvial fan and interfingering proglacial deposits. The cross-cutting relationships allow the deformational structures to be arranged into a chronological sequence: 1 - soft sediment convection deformations within the lacustrine interlayers, 2 - normal planar faults and shear zones and, 3 - Iistric normal faults. The occurrence and the orientation of planar normal faults and shear zones shows close correlation with the strain ellipse connected with left-lateral shear couple along the Sudetic Marginal Fault. The displacement of fan apex in relation to supplying river outlet, shingled arrangement of successive fan lobes and occurrence and orientation of structures typical of shear couple along the major strike-slip fault seem to be useful criteria to distinguish alluvial fans on strike-slip faults.
Summary
Synsedimentary tectonic activity along the Sudetic Marginal Fault, SW Poland, resulted in the evolution of an alluvial fan sedimentary system and development of deformational structures in a sequence of Plio-Pleistocene sediments. The early phase of sedimentation, related to the dip-slip effect of the Sudetic Marginal Fault, resulted in progradation of alluvial fan at the outlet of the Pre-Kaczawa River onto the downthrown Fore-Sudetic Block. The following strike-slip movements along the fault induced the shingled arrangement of successive fan lobes and development of deformational structures in alluvial fan and interfingering proglacial deposits. The cross-cutting relationships allow the deformational structures to be arranged into a chronological sequence: 1 - soft sediment convection deformations within the lacustrine interlayers, 2 - normal planar faults and shear zones and, 3 - Iistric normal faults. The occurrence and the orientation of planar normal faults and shear zones shows close correlation with the strain ellipse connected with left-lateral shear couple along the Sudetic Marginal Fault. The displacement of fan apex in relation to supplying river outlet, shingled arrangement of successive fan lobes and occurrence and orientation of structures typical of shear couple along the major strike-slip fault seem to be useful criteria to distinguish alluvial fans on strike-slip faults.